Mineral chemistry and fluid inclusion composition as petrogenetic tracers of iron oxide-apatite ores from Hormuz Island, Iran

Journal of African Earth Sciences 155 (2019) 90–108

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Mineral chemistry and fluid inclusion composition as petrogenetic tracers of iron oxide-apatite ores from Hormuz Island, Iran

T

Narges Sadat Faramarzia, Mahboobeh Jamshidibadra,∗, Soraya Heuss-Assbichlerb, Gregor Borgc a

Department of Geology, Payame Noor University, PO BOX 19395-4697, Tehran, Islamic Republic of Iran Department for Earth and Environmental Sciences, LM-Universität München, Theresienstr. 41, 80333, Munich, Germany c Institute of Geosciences and Geography, Martin Luther University Halle-Wittenberg, Germany b

A R T I C LE I N FO

A B S T R A C T

Keywords: Iron oxide Fluorapatite Mineral chemistry Fluid inclusion Hormuz island Iran

Hormuz Island is a salt diapir in southern Iran, which also comprises transported blocks of rhyolitic and rhyodacitic rocks, which were brought to the surface during the island's diapiric emergence from the Persian Gulf. The rhyolites (558 ± 7 Ma) and rhyodacites, have both formed from the same peraluminous calc-alkaline I-type magma, in a volcanic arc settings at an active continental margin. The volcanic rocks contain significant quantities of accessory apatite. The majority of the small crystals of apatites (type-I) have crystallized during an early magmatic phase. Additionally, large single crystals of apatite (type-II) occur together with magnetite in veins within the rhyodacite rocks. The geochemical investigation of the two types of apatite revealed they both formed from the same magma source. Based on the microthermometric characteristics of primary fluid inclusions, two different events during the formation of apatite type-II crystals were distinguished. Our study revealed that in addition to the igneous fluids, a second set of fluid inclusions was trapped in the core of the crystals, indicating a post magmatic interaction with external basinal fluids during the growth of apatite type-II. On Hormuz Island, iron oxides occur as well in different styles from massive iron oxide bodies, magnetite-apatite veins, to red magnetic-hematitic soils. Based on the volcanic structures and textures of the massive iron oxide bodies as well as geochemical results from the magnetite, it is proposed that a source potential for both Fe and P could have been an immiscible iron-rich volatile phase which evolved from the parental felsic magma. Results from fieldwork, microscopy, and geochemistry revealed that mega-crystals of hematite and specularite in the magnetite-apatite veins were formed from magmatic-hydrothermal fluids released from the crystallizing magmas. The occurrence of exotic banded iron ores, red soils and alternating bands of hematite with evaporite minerals could be the result of seawater-rhyolite interactions by circulating exhalative hydrothermal fluids.

1. Introduction Apatite, Ca5 (PO4)3(F, OH, Cl), is an accessory mineral occurring in a wide range of rock types. It is one of the most important carrier minerals of phosphorus and volatiles in igneous rocks (Broska et al., 2004). Commonly, granites and rhyolites contain up to 0.5 wt % P2O5, mostly concentrated in apatite (Cao et al., 2012). Apatite is a common type of mineral with the ability to contain and thus record geochemical information about the parental magma and its evolution process (Chu et al., 2009). The incorporation of high amounts of trace-elements, including rare-earth elements, Sr, Mn and Th (Roeder et al., 1987) in apatite, make it a particularly good petrogenetic tracer or indicator mineral. Additionally, apatite commonly hosts fluid inclusions, which can be studied with the aim to understand the nature and evolution of the coexisting magmatic or hydrothermal fluids. Studying such fluid ∗

inclusions provides a powerful tool to reveal the physico-chemical conditions of the parental magma (e.g. temperature, pressure, and salinity) during apatite mineralization. In addition to apatite, magnetite is also useful as an indicator mineral to record the source rock composition. Magnetite forms either at a relatively low temperature from hydrothermal fluids (Nadoll et al., 2012) or it can crystallized from high temperature silicate and sulfide melts (Dare et al., 2014). Magnetite is a common ore mineral in banded iron formations (BIF; Nadoll et al., 2012) but is also found in varying amounts in a wide variety of geological environments (Lindsley, 1991; Dare et al., 2014). A variety of elements with similar ionic radii to Fe2+ and Fe3+ can substitute in the magnetite structure (e.g., Mg, Al, Si, P, Ca, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Sn, Ce; Nadoll et al., 2012). Magnetite is also relatively resistant to surface weathering, and thus can be useful for petrogenetic studies (e.g. Nadoll et al., 2012; Broughm et al., 2017). For example, by using trace

Corresponding author. E-mail address: [email protected] (M. Jamshidibadr).

https://doi.org/10.1016/j.jafrearsci.2019.03.018 Received 16 July 2018; Received in revised form 20 February 2019; Accepted 20 March 2019 Available online 16 April 2019 1464-343X/ © 2019 Elsevier Ltd. All rights reserved.

Journal of African Earth Sciences 155 (2019) 90–108

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Fig. 1. Simplified geological map of Hormuz Island (Faramarzi, 2015) in south Iran, showing the distribution of rhyolites and rhyodacites. The star depicts the occurrence of the apatite veins.

Gondwana margin where convergent (Proto-Tethyan) and extensional (Najd) tectonic regimes coexisted at that time (Allen, 2007; Faramarzi et al., 2015a, b; Faramarzi et al., 2017). Such a depositional environment made the Middle East one of the world's largest evaporite provinces and is well preserved in southern Iran (Hormuz Formation), Oman (Ara Group), India, Pakistan, Saudi Arabia, Jordan etc. (e.g. Faramarzi et al., 2015a, b; Reuning et al., 2009). Evaporites and carbonates of the Hormuz Formation exposed in southern Iran have been observed in over 200 salt-gypsum diapiric domes, with Hormuz Island, located in the Persian Gulf, being one of the most impressive ones (e.g. Edgell, 1996). Hormuz Island shows a concentric structure in the central part and consists mainly of colorful evaporites (halite, gypsum, sylvite, and anhydride). Generally, iron had the greatest impact on the coloring of the evaporites but other elements have also a minor effect (Faramarzi, 2015). During the island's diapiric rise and eventual emergence from the Persian Gulf, the Hormuz Dome transported blocks of “exotic” igneous, pyroclastic, sedimentary, and low-grade metamorphic rocks as mega xenoliths to the surface (Fig. 1). These non-evaporitic rocks occur concentrically, mainly in the outer parts of the central salt deposit. The various sedimentary and volcanic lithotypes comprise dolomite, limestone to sandy limestone, Fe oxide layers, pyroclastic rocks (rhyolitic tuffs and ignimbrites) and volcanic rocks (rhyolite, rhyodacite, trachyte and diabase). Pyroclastic rocks are more common in outcrops compared to volcanic igneous ones. A brecciated ferruginous ring with a thickness between 18 and 117 m, surround the aforementioned rocks. This ring is predominantly composed of angular fragments of sedimentary and igneous rocks, which have mostly been cemented in a fine-crystalline matrix of magnetite and hematite. In some parts, blocks of magnetite with flow layering, vesicular iron-ore fragments, ash-like crystalline hematite, sandy magnetite, and layered hematite-jaspilite occur irregularly scattered within in this ferruginous concentric zone. MiocenePliocene and Recent sediments occur predominently in the outer parts of the island near the coast line. The Hormuz rhyolites (with zircon UePb age of 558 ± 7 Ma) and rhyodacites formed from subductionrelated magmas, generated in an active continental margin setting (Faramarzi et al., 2015a, b). Field observations and microscopic studies

element chemistry of magnetite it is possible to distinguish processes involved during magnetite crystallization (e.g. magmatic, hydrothermal or a combination of them; Broughm et al., 2017). The salt diapir of Hormuz Island in the Persian Gulf exposes also blocks of rhyolite and rhyodacite, which were transported to the surface together with salt and gypsum of the diapir sensu stricto (Fig. 1). These volcanic rocks contain significant quantities of relatively small crystals of apatite (apatite type-I) as accessory minerals, which have probably crystallized during the early magmatic phase. In addition, some polymictic veins cutting across rhyodacitic rocks contain megacrysts of apatite, rich in fluid inclusions (apatite type-II) and also of magnetite. Fission-track dating of the apatite type-II yielded an age of 55.4 ± 2.6 Ma for a cooling temperature of approximately 100 °C (Hurford et al., 1984). The question arises if these two different types of apatite share a common geological history or if they have formed by separate, unrelated processes. Previous studies have shown that an intensive, post-magmatic hydrothermal event has affected the rocks of Hormuz Island (Faramarzi, 2015) and other parts of the Hormuz Formation (Mortazavi et al., 2017). In our present investigation, we studied the petrography and geochemistry of the Hormuz Island apatites and their fluid inclusions as well as the composition of the iron oxides with the aim to answer the following three questions: (1) What is the origin of the iron oxides and the two types of the Hormuz Island apatite, e.g. magmatic, hydrothermal or both? (2) What is the petrogenetic relationship between the iron oxides, apatites and the Hormuz Island magmatism? (3) Which information do these minerals provide about the magmatic evolution of Hormuz Island? Our study is based on the results from fieldwork, microscopy, geochemistry and fluid inclusion analyses of apatites from Hormuz Island rhyolites, rhyodacites, and vein mineralization within rhyodacite rocks as well as of the iron oxide mineralization. 2. Geological setting During the Late Neoproterozoic to Early Cambrian (Ediacaran), an evaporite depositional environment predominated along the northern 91

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Fig. 2. A) Rhyolite outcrop on Hormuz Island. B) Rhyodacite from the southern part of the island with veins containing single apatite crystals (type-II). C) Hand specimen of rhyodacite showing up to 1 cm sized apatite crystals type-II on the wall of the vein; D) Apatite metacrysts type-II up to 2 cm in size. Table 1 XRF analysis (for oxides) from the Hormuz Island rhyolites and rhyodacites. Lithology

Rhyolite

Rhyodacite

Sample

FH-12

FH-14

FH-22

FH-23

FH-49

FH-53

FH-72

FH-94

PH-102

PH-104

PH-112

PH-132

FH-29

FH-69

FN-6

HN-39

HN-56

SiO2 (wt. %) TiO2 Al2O3 Fe2O3 MnO MgO CaO Na2O K2O P2O5 LOI Total

69.1 0.38 13.1 3.63 0.07 1.28 0.54 0.90 8.85 0.08 1.64 99.6

72.5 0.36 13.8 0.91 0.03 1.03 0.34 4.35 5.59 0.06 0.89 99.9

71.0 0.27 13.2 2.60 0.06 2.37 0.72 2.93 4.56 0.07 2.04 99.8

69.6 0.72 13.6 2.40 0.04 1.80 1.45 3.70 4.62 0.13 1.23 99.3

74.6 0.15 11.7 0.97 0.01 0.19 0.39 0.44 10.8 0.03 0.69 100

73.7 0.19 11.5 0.79 0.00 2.25 0.45 0.42 9.67 0.02 0.91 99.9

73.3 0.20 13.2 2.12 0.03 1.07 0.08 0.58 6.85 0.03 2.02 99.5

72.9 0.35 13.3 2.98 0.03 2.56 0.31 0.85 5.04 0.07 1.57 100

67.6 0.39 13.3 4.74 0.07 1.21 0.59 1.03 9.11 0.09 1.70 99.8

70.9 0.35 14.0 2.01 0.02 0.98 0.31 4.18 5.69 0.07 1.30 99.8

68.7 0.27 12.9 4.54 0.05 2.35 0.75 2.96 4.36 0.07 2.90 99.9

72.1 0.20 12.1 3.82 0.03 1.60 0.06 0.47 7.12 0.03 2.40 99.9

68.6 0.49 14.1 3.74 0.08 3.51 3.38 1.30 3.54 0.15 0.20 99.1

67.3 0.57 13.3 4.31 0.11 3.50 4.37 3.21 2.04 0.17 0.21 99.1

67.1 0.58 14.2 3.76 0.09 3.08 4.35 3.53 2.64 0.14 0.11 99.6

68.1 0.49 13.5 3.88 0.03 3.24 4.11 4.02 2.06 0.21 0.11 99.8

68.6 0.53 14.1 4.05 0.06 2.78 4.29 3.84 1.52 0.23 0.10 100.1

Iranian salt diapirs. In addition to megacrystals of apatite type-II and euhedral crystals of hematite, some coarse grained euhedral shape minerals (e.g. ferro-augite, albite, amphibole, tourmaline, dolomite, and pyrite) are also observed in the Hormuz Island rocks. The idiomorphic shape and the relatively large size of these minerals may indicate the prominent role of hot hydrothermal fluids during their crystallization.

show that the volcanism occurred at least partly simultaneously with the deposition of the evaporites and carbonate sediments. The rhyolites are exposed more commonly in outcrops than the rhyodacites, the latter being only observed in two outcrops in the southern part of the island (see Figs. 1 and 2 A-B). The rhyodacites show a porphyritic texture and are strongly fractured and brecciated. Typically, the rhyodacites consist of fragments with reddish color and different sizes ranging from < 10 cm to several meters, embedded in the surrounding brecciated ferruginous ring. Within these rhyodacitic fragments, poly-mineral veins (described below) with a thickness between 1 and 50 cm occur and these host single megacrystals of apatite type-II (Fig. 2 B). Furthermore, many apatite type-II crystals occur scattered in the decomposed groundmass of the rhyodacite, with the decomposition caused by brecciation and intense alteration of the rocks (Fig. 2C and D). At Esfordi, Choghart, Zarigan and some other localities of Iran, crystalline apatite mineralization occurs in association with iron ore and felsic volcanic rocks (Sabet-Mobarhan-Talab et al., 2015). In these areas apatite occurs in veinlets and disseminated within the iron ores. The abundance of hematite, varying from powder-like ochre to euhedral hematite and specularite crystals is also a noticeable feature in most

3. Sample materials and analytical techniques A total of twelve rhyolitic and five rhyodacitic rock samples were initially studied by microscopy and subsequently selected for whole rock analysis. The altered and fractured parts of the samples were cut off to obtain the least altered rock portion. The samples were pulverized to < 74 μm using an agate mill. The major elements were analyzed by X-ray fluorescence (XRF) and minor and trace elements by inductively coupled plasma mass spectrometry (ICP-MS). The whole rock chemistry of six samples of banded iron ore and red soil were additionally determined by ICP-MS. The XRF analyses were carried out using a Panalytical Axios instrument with Super Q analytical software at the 92

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Table 2 ICP-MS analysis (for trace elements) from the Hormuz Island rhyolites and rhyodacites. Lithology

Rhyolite

Rhyodacite

Sample

FH-12

FH-14

FH-22

FH-23

FH-49

FH-53

FH-72

FH-94

PH-102

PH-104

PH-112

PH-132

FH-29

FH-69

FN-6

HN-39

HN-56

Zr (ppm) Hf U Th Y Rb Ta Nb Co La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu ∑ REE Th/Ta

152 4.18 5.11 11.7 37.2 190 0.78 7.02 4.01 21.9 44.2 5.35 20.1 0.39 0.58 4.99 0.72 4.50 0.98 2.44 0.31 1.99 0.23 109 15.0

121 6.57 3.32 11.5 55.8 147 0.77 7.80 1.78 44.0 87.9 9.52 35.8 8.01 1.57 7.41 1.36 6.32 1.34 3.89 0.48 3.07 0.42 211 14.9

137 4.40 3.41 11.8 32.9 107 0.82 8.49 3.05 35.1 73.6 8.58 32.1 6.26 1.30 5.53 0.76 5.23 1.06 2.50 0.43 2.12 0.27 175 14.4

138 6.76 2.38 10.9 36.6 106 0.89 9.55 2.87 23.5 48.8 6.06 24.3 4.12 1.28 5.18 0.81 5.17 1.00 2.43 0.41 2.46 0.28 126 12.2

95.2 3.85 2.21 12.7 29.3 63.2 0.76 9.21 2.26 7.31 15.9 2.01 7.32 2.27 0.82 2.52 0.44 2.40 0.60 1.21 0.23 1.29 0.19 44.5 16.7

137 3.71 4.09 10.3 24.0 182 0.81 4.75 0.03 3.13 6.51 0.66 2.31 0.53 0.56 0.61 0.07 0.46 0.10 0.23 0.05 2.19 0.03 17.4 12.7

98.8 6.29 6.56 11.5 27.5 141 0.70 10.2 2.16 7.73 16.6 2.91 9.72 2.02 0.48 1.18 0.22 1.22 0.34 1.51 0.30 2.09 0.09 46.4 16.4

120 4.84 2.92 10.1 27.3 130 0.73 9.01 3.78 14.8 37.4 4.33 17.8 3.50 0.41 2.45 0.30 0.09 0.23 0.35 0.08 1.31 0.07 83.2 13.8

151 4.70 2.80 10.4 27.8 188 0.72 7.50 6.61 26.2 47.6 5.82 20.6 4.76 0.60 5.01 0.71 4.92 0.93 2.58 0.44 2.87 0.43 124 14.4

124 4.20 3.20 10.5 37.2 139 0.70 7.51 1.20 58.1 98.7 11.3 39.4 7.36 1.16 7.11 1.09 6.86 1.34 4.04 0.55 3.74 0.52 241 15.0

138 4.30 3.30 11.5 22.1 105 0.71 6.80 4.51 41.8 73.2 8.73 33.0 5.22 0.70 4.96 0.67 3.95 0.76 2.40 0.35 2.52 0.40 179 16.2

80.2 6.80 5.60 14.8 16.4 130 0.80 9.31 1.60 43.9 55.1 10.2 36.7 4.99 0.36 1.75 0.32 2.13 0.61 2.25 0.42 3.42 0.54 163 18.5

122 7.15 3.93 11.9 48.3 86.3 0.88 8.61 4.14 31.9 63.2 6.89 26.7 6.77 0.21 5.23 1.04 5.40 1.12 2.93 0.43 2.78 0.49 155 13.5

111 9.24 4.82 12.5 43.1 118 0.93 12.7 6.38 54.1 104 10.2 44.0 10.5 0.52 8.41 1.08 6.63 1.31 3.56 0.54 3.34 0.58 249 13.4

146 7.18 5.31 7.50 27.2 100 1.01 10.4 4.40 45.0 98.3 9.44 39.9 8.39 0.36 6.54 1.05 6.13 1.27 2.90 0.44 2.67 0.44 223 7.43

138 8.09 4.71 6.94 38.1 98.9 0.96 10.1 5.21 33.5 67.4 7.04 27.6 6.54 0.32 5.21 1.04 6.07 1.21 2.96 0.45 2.79 0.47 163 7.23

121 9.13 5.04 9.88 33.8 112 1.05 9.88 4.80 27.9 57.2 6.03 24.9 5.98 0.28 5.52 0.96 5.38 1.11 2.73 0.42 2.78 0.43 142 9.41

Fig. 3. A) Apatite type-I crystal in the groundmass of rhyolite in PPL and B) in XPL; C) Apatite type-I and zircon as inclusions in biotite within rhyolite in PPL and D) in XPL; (Ap: apatite, Chl: chlorite, Zrn: zircon, Bt: biotite).

Wittenberg, Germany. Minerals, which could not be identified by polarized light microscopy, were analyzed semi-quantitatively using the SEM-EDX (including SEM-mapping) technique. Thin sections for SEM work were coated with carbon. Analytical EDX settings were 20 kV beam voltage and a count time of 60 s (peaks). Major and minor elemental compositions of three apatite crystals (from rhyolites) and seven magnetites (coexisting with vein-type apatite type-II) were analyzed by electron microprobe analyses (EMPA) using a JEOL 8200 Super Probe at the University of California, Los

University of the Free State (South Africa). The accuracy was < 1% for SiO2 and Al2O3 and 5% (relative) for the other oxides. The whole rock ICP-MS analyses were conducted at ACME Laboratories (Canada) following a lithium metaborate/tetraborate fusion and nitric acid digestion of 0.2 g sample powder. The detection limit for trace elements (including the REE) by ICP-MS is ∼0.01 ppm. Scanning electron microscopy (SEM) with an energy dispersive spectrometer has been carried out using a GEOL JSM6300 at the Institute of Geological Sciences of the Martin-Luther University Halle93

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Fig. 4. SEM-element mapping images of biotite with apatite inclusions in a rhyolitic sample (FHe50P-6). Element distribution map of Al, K, Mg, Ca, Fe, Na, Cl, Ti and P showing inclusions of apatite type-I in biotite (see also points 1 and 2 in Table 3). The apatite is recognizable by high concentrations of P and Ca in this map. The high Ti concentrations stem from rutile inclusions.

were pulverized to < 74 μm, using an agate mill, and the powders were analyzed by ICP-MS for minor and trace elements. The ICP-MS analyses on apatite type-II were also conducted at ACME Laboratories (Canada). For studying fluid inclusions, three doubly polished thin sections (200–250 μm thickness) of type-II apatite were prepared. Fluid inclusion microthermometry was carried out on inclusions in apatite type-II using a Linkam THM600 heating-freezing stage, fitted with a thermal control unit TMS-93 and equipped with Zeiss microscope at the Kharazmi University of Iran by applying standard procedures (Shepherd et al., 1985). The heating-freezing stage allows measurements within the range of −90 °C to +550 °C. Freezing and heating runs were undertaken, respectively, using liquid nitrogen, and a thermal resistor calibration of the stage was carried out by using standard natural and synthetic inclusions. The accuracy of the temperature measurement is about ± 0.1 °C in the low temperature range

Angeles (UCLA). The operating conditions were 15 kV accelerating voltage, 20 nA beam current, a spot size varying from 1 to 3 μm and counting times of about 30 s or 40000 counts. Standards for the point analyses consisted of a suite of C.M. Taylor Company mineral and synthetic standards. Cl standard using the Sodalite standard followed the procedures of Sharp et al. (1989). Analytical precision for most elements is better than 1%, except for F and Cl which is around 4%. It is important to note that any exsolution of ilmenite present in magnetite were incorporated into the analysis and thus better represent the initial composition of the Fe oxide before a subsolidus oxyexsolution process of ilmenite occurred (Dare et al., 2014). 50 single-grain apatite (type-II) crystals with different sizes and the least number of fractures were selected from the veins occurring in rhyodacite rocks. The crystals were washed in three steps with pure distilled water to eliminate surface contamination. Selected crystals 94

Journal of African Earth Sciences 155 (2019) 90–108

– – – – 0.00 0.00 0.70 0.00 0.10 – – – – – – 0.00 0.00 7.60 0.00 0.00 – –

4.1. Petrology and geochemical composition

– – – – 0.00 0.00 3.20 1.00 0.00 – –

4.1.1. Whole rock petrology The rhyolites show a porphyritic texture. Quartz, sanidine, sodic plagioclase, biotite, and hornblende occur as major minerals (phenocrysts) along with apatite, monazite, zircon, tourmaline, FeeTi oxides, ilmenite, rutile, and more rarely epidote as accessory minerals. The rhyodacitic rocks show also a porphyritic texture. They are composed of quartz, sanidine, plagioclase, and hornblende as major minerals (phenocrysts), and contain monazite, zircon, fine-crystalline mica, ilmenite, rutile, and chlorite as accessory minerals. Whole rock major and trace-element analyses of the rhyolites and rhyodacites of the Hormuz Island are provided in Tables 1 and 2. Both rock types have undergone drastic changes during their ascending passage together with the diapiric salt dome and these rocks are consequently altered due to intensive contact with rock salt and evaporites. The rhyolites contain 67.6–74.6 wt % SiO2, high levels of K2O (4.36–10.8 wt %), comparatively low amounts of Na2O (0.44–4.35 wt %) and CaO (0.06–1.45 wt %). The rhyodacites contain 1.30–4.02 wt % Na2O and are characteristic by lower amounts of SiO2 (67.1–67.6 wt %) and K2O (1.52–3.54 wt %) with higher concentrations of CaO (3.38–4.35 wt %).

– – – – 1.70 0.00 33.5 0.60 0.00 – – – – – – 0.00 0.00 0.60 0.00 0.00 – – 20.9 20.3 14.2 16.9 15.1 0.00 13.1 12.4 0.00 0.00 0.00

4.1.2. Apatite Type-I Apatite is a relatively abundant accessory mineral in the rhyolites of Hormuz Island. The apatite of type-I exhibits typically euhedral hexagonal prisms of 0.1–0.6 mm diameter. Apatite crystallized not only in the groundmass (Fig. 3A and B) but also occurs as inclusions within biotite (Fig. 3C and D). Due to the extensive chloritization of biotite, the small apatite inclusions cannot be easily identified by polarization microscopy. High concentrations of P and Ca in element mapping by SEM-EDS (Fig. 4) allowed for the identification of numerous small apatite inclusions within the biotite. SEM and EPMA analyses (Tables 3 and 4, respectively) show very low Cl concentrations of these apatites, whereas they contain F concentrations of up to 3.99 wt % and hence are classified as fluorapatite. In general, the apatites are free from inclusions, and only few crystals contain small inclusions of magnetite and monazite. In the rhyodacite, apatite type-I with a size of 0.01–0.2 mm was observed as inclusions within hornblende (Fig. 5 A) and feldspar (Fig. 5 B; Table 3). Microanalyses of these apatites show high concentrations of F (up to 4.29 wt %) and low concentrations of Cl (up to 0.45 wt %), and thus they can also be classified as fluorapatite (Table 3).

H-AP5

H-AP4

H-AP1

FH-69-2

4.1.3. Apatite Type-II Apatite type-II occurs typically as relatively large subhedral to euhedral bipyramidal hexagonal prisms. The apatite type-II displays a wide range of crystal sizes from 1 mm up to 12 cm (Fig. 6A and B). These apatite megacrysts occur together with monazite, fluorite, hematite, magnetite, ilmenite and quartz in veins within the rhyodacite. These type-II apatites are commonly fractured and occur preferentially in a decomposed groundmass including smaller sized apatite, monazite, and hematite (Fig. 6 C). The surrounding rocks are generally strongly altered and contain albite, quartz, fine-crystalline mica, allanite and tourmaline. Apatite type-II usually host few monazite and magnetite inclusions in their central parts (Fig. 6 D) and may contain numerous inclusions of magnetite in the rims of these apatite crystals. In addition, magnetite and fluorite exist in the more fractured and brecciated parts of the veins

Vein within rhyodacite

Vein within rhyodacite

Apatite type-II Magnetite Monazite Apatite type-II Fluorite Fluorite Magnetite Vein within rhyodacite

Rhyodacite

Apatite type-I as inclusion in feldspate

27.0 23.6 45.9 41.0 41.4 30.3 19.3 50.3 3.70 0.00 29.8 1 2 1 2 1 2 3 1 2 1 2 FH-50-6

Rhyolite

Apatite type-I as inclusion in biotite

3.57 3.27 4.29 4.11 2.80 0.00 0.00 1.90 52.3 50.3 0.00

0.00 0.25 0.00 0.00 – – – – – 17.8 0.00

0.00 0.16 0.00 0.00 – – – – – 8.00 0.00

0.27 0.24 0.23 0.20 0.20 0.00 0.00 0.30 0.00 19.2 0.00

0.86 0.50 0.45 0.31 0.70 0.00 0.00 0.50 0.00 – –

47.4 51.5 34.5 37.3 36.5 0.00 1.4 32.2 44.0 47.7 0.00

0.00 0.20 0.46 0.27 0.00 58.6 0.00 0.60 0.00 0.00 68.9

– – – – 0.60 0.00 0.00 0.20 0.00 – –

– – – – 0.00 11.1 0.00 – – 0.00 1.20

Ce La Ti S Na Fe Ca Cl P Si Al Mg F O Mineral Rock point Sample

Table 3 Chemical composition of analyzed minerals using SEM (Figs. 4–6).

2.00 – – – – – 1.70 0.00 33.5 0.60 0.00 – –

Nd

4. Results

Sr Sm

(−190 to 50 °C) and ± 2 °C in the high temperature range (100–550 °C). The salinity of aqueous fluid inclusions was calculated based on the Bodnar (2003) equation and the density was calculated by using the equation proposed by Brown and Lamb (1989).

Pr

N.S. Faramarzi, et al.

95

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Table 4 Chemical composition of an apatite type-I from rhyolite (sample FHe 22 A) analyzed using EPMA. Analysis point

P2O5

SiO2

FeO

MnO

CaO

Na2O

K2O

La2O3

Ce2O3

F

Cl

S

Total

89-FH-22A-1 89-FH-22A-2 89-FH-22A-3

39.1 38.8 39.5

0.3 0.31 0.31

0.07 0.09 0.12

0.01 0.04 0.02

53.1 53.4 53.7

0.42 0.34 0.38

0.01 0.00 0.01

0.53 0.42 0.47

1.43 1.03 1.02

3.12 3.99 3.54

0.77 0.72 0.66

0.23 0.17 0.24

99.1 99.2 100

Calculation based on 26 (O, OH, F, Cl, S) 89-FH-22A-1 89-FH-22A-2 89-FH-22A-3

P 5.90 5.90 5.90

Si 0.00 0.00 0.10

Fe 0.00 0.00 0.00

Mn 0.00 0.00 0.00

Ca 9.80 10.1 9.70

Na 0.10 0.10 0.10

K 0.00 0.00 0.00

La 0.00 0.00 0.00

Ce 0.10 0.10 0.10

F 1.30 1.20 1.10

Cl 0.10 0.10 0.10

S 0.10 0.10 0.10

Fig. 5. A) BSE image from rhyodacite showing apatite type-I and sphene as inclusions in hornblende. B) BSE image from rhyodacite showing apatite inclusions (points 1 and 2) hosted in feldspar (sample FH-69-2; Table 3).

(Fig. 6 E − F; Table 3). SEM element mapping images (Fig. 7) from the central part of the vein toward the contact of the vein with the rhyodacitic wall rock clearly show abundant P, Ca, Fe, Ti, and Mg pointing to the occurrence of apatite, magnetite, and hematite along this section. The rhyodacitic rocks were obviously effected by crystallization of calcite, as indicated by Ca-rich veins in the groundmass. The chemistry of apatite type-II is shown in Tables 3 and 5, respectively. The crystals contain high amounts of F (av. 3.41 wt %) and low concentrations of Cl (av. 0.02 wt %) and hence are also classified as fluorapatite.

rocks (Fig. 8 E) may indicate a magmatic origin for these massive ironoxide bodies. 4.1.4.2. The brecciated ferruginous ring. The ferruginous ring is predominantly composed of angular fragments of all sorts of country rocks, which have been cemented in a red, fine-crystalline hematiterich matrix. The fragments show different sizes and range from < 1 cm to 1 m in diameter. The fragments consist mostly of broken and brecciated pieces of the island's volcanic, volcanoclastic, and sedimentary rocks, which have been brecciated probably due to salt tectonics and salt diapirism (Fig. 8 F). The matrix consists of magnetite, hematite, quartz, chlorite, sericite, halite, gypsum, and FeeMn-bearing clays. Although magnetite is the first ubiquitous mineral, all gradual transitions of magnetite to hematite, i.e. martitization can be recognized (Fig. 8 G). In some parts, blocks of “sandy” magnetite and hematite are scattered within the ferruginous ring. These blocks show an unconsolidated, laminated fine-grained structure and are mostly less than 1 m thick (Fig. 8 H).

4.1.4. Iron oxides 4.1.4.1. At Hormuz Island, the iron oxides occur in different styles as will be described below: massive iron-oxide bodies. The term massive is used here for a type of iron mineralization with igneous textures and without any bedding or lamination. These massive iron oxide ore bodies show evidence of an ortho-magmatic origin such as contorted flow layering (Fig. 8 A) and vesicular textures with open vesicles, possibly suggesting a magnetite-rich extrusive “lava” flow. At Hormuz Island, the vesicular iron-ore fragments are up to tens of centimeters in diameter and occur scattered in the ferruginous outer ring of the island (Fig. 8 B). These iron oxide rocks have the appearance of basaltic scoria and seems to have formed by a strombolian-like eruption of an iron-oxide magma. Similar vesicular textures are common in many of the massive magnetite units of magmatic origin (e.g. at the El Laco volcano, Chile; Naslund et al., 2002). Ash-like crystalline hematite rocks seem to be another feature for the eruption of iron oxides as pyroclastic flows (Fig. 8 C). These rocks show also vesicular textures with spherical open vesicles. These vesicular textures are hard to reconcile with an origin by hydrothermal alteration or replacement, which usually fills pores and vesicles during the initial stages of alteration. However, some of the few subvolcanic ore bodies, which crosscut the ferruginous outer ring of Hormuz Island, are magnetite dykes with up to < 2 m width. These dykes are strongly brecciated and therefore the contact with the surrounding wall rocks are not always clear (Fig. 8 D). Additionally, crosscutting magnetite veins (1 mm to > 10 cm wide), which have cemented the strongly altered and fractured rhyolitic host

4.1.4.3. Banded iron stones. Alternating bands of hematite and evaporite minerals are a common rock unit in the central part of Hormuz Island (Fig. 9 A). During field work, we identified outcrops of layered hematite-jaspilite within the ferruginous ring. However, due to the scale of mapping and the high degree of brecciation it was not possible to graphically show this unit separately from the ferruginous ring in the geological map (Fig. 1). Atapour and Aftabi (2017, see Fig. 9 B) reported bullet-shape dropstones, composed of sericite, epidote, cherty dolomitic marbles, and metamorphosed mudstones within the jaspilitic banded iron unit. These authors proposed that the dropstones belong to the global Late Ediacaran glaciation. However, due to the lack of isotopic and geochronological age data from fragments within the hematite-jaspilite layers and also the lack of other traces of glaciation (e.g. glacial striation marks) on Hormuz Island, it still remains an open question, if these are banded iron formations and have a cryogenic origin. Alternatively and given the spatial association with the vesicular iron oxide rocks on Hormuz Island, we rather suggest that these rocks have formed as an iron oxide ignimbrite, which is a common feature in 96

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Fig. 6. A) Microphotograph of euhedral apatite typeII crystallized within veins of rhyodacites in PPL and B) in XPL. C) BSE image from the central parts of the vein showing apatite type-II coexisting with monazite and hematite. D) BSE image showing magnetite (point 2) and monazite (point 3) as inclusions in the previous apatite type-II (sample H-AP1; Table 3). E) BSE image from brecciated parts of the vein, which show apatite type-II crystals coexisting with hematite and fluorite (sample H-AP4; Table 3). F) BSE image from decomposed parts of the vein, which show apatite type-II, quartz, hematite, fluorite and magnetite (sample H-AP5; Table 3).

rocks in the outer parts of the island. The specularite mostly occurs as scattered fragments with hematite aggregates up to 2 cm in length (Fig. 9 F). Bosak et al. (1998) believe that the presence of specularite on fissure and vugs in the Hormuz Formation is related to mineral leaching during hydrothermal activity.

several other magmatic massive iron-oxide bodies (e.g. at the Durango deposits in Mexico; Mungall et al., 2012; see Fig. 9 C). 4.1.4.4. Mega-crystals of hematite. Commonly, hematite shows tabular, rhombohedral, and occasionally prismatic or pyramidal crystal shapes. However, the hematite mega-crystals of Hormuz Island display hexagonal bipyramidal and hexagonal prismatic shapes, which are globally a rare phenomenon. The Hormuz hematites occur as euhedral to subhedral crystals (ranging in size from 4 to 7 cm) within veins or in cavities in halite rocks. Due to the intense solubility of salt, hematite mega-crystals occur also scattered over many parts of the island, where they form residual hematites after dissolution of the salt rocks, especially along the brecciated ferruginous ring (Fig. 9 D).

4.1.4.7. Red soil (ochre). From field observation, it can be assumed that the “Red Soil” derives its color from a mixture of hematite and iron hydroxides (FeOOH). The overall color, however, is more violet-reddish rather than orange to yellow. A predominance of hematite over the iron hydroxides is thus assumed. The red ocher hematite, which has been mined in numerous other locations of the Hormuz Formation salt domes, occurs in the south-western part of Hormuz Island. The red ochre consists of coherent fragments scattered in a red color soil. Specularite, quartz, and sericite are the main minerals in the coherent fragments (Fig. 9 H). Rounded aggregates of minerals such as hematite, quartz, calcite, dolomite, apatite, and ilmenite are other distinguishable minerals within the red color soil. In addition to Fe, iron oxides from Hormuz Island contain important major, minor and trace elements, which were analyzed using EPMA and ICP-MS. The representative results of EMPA analysis for magnetite (which crystalized in veins within the rhyodacitic rocks and are coexisting with apatite type-II) presented in Table 6, and the results of ICPMS analysis for banded iron and red soil are shown in Table 7. Detailed mineral chemistry of the magnetite grains (Table 6) show wide ranging concentrations of Al2O3 (0.16–0.01 wt %), TiO2 (4.02–0.03 wt %), MgO (0.04–0.01 wt %), V2O3 (0.45–0.12 wt %), NiO (0.02–0.06 wt %), SiO2

4.1.4.5. Magnetite and hematite coexisting with apatite Type-II. Magnetite and hematite occur also together with apatite type-II, monazite, fluorite, ilmenite, and quartz in veins within the rhyodacitic rocks (Fig. 6 E). Magnetite forms typically subhedral to euhedral crystals or aggregates with an average size of 200 μm diameter, but locally up to 1 mm. Some magnetites show exsolution of ilmenite (visible in BSE image; Fig. 9 E), which is a common texture found in magmatic magnetite, crystallized in hot and reduced settings (Mehdilo and Irannajad, 2010). 4.1.4.6. Specularite (oligist). Coarse aggregates of euhedral hematite, forming specularite occur commonly within crosscutting veins and in open vugs of the ferruginous ring, in rhyolitic tuffs, and in sedimentary 97

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Fig. 7. SEM element mapping images showing the contact between the vein (right side) and the host rhyodacite (left side). The rhyodacite is rich in O, Si, Al, and K, indicating quartz and K-feldspar, whereas the vein part contains high amounts of Ca, Fe, Ti, and P due to crystallization of apatite, magnetite, hematite, and ilmenite.

shaped and occur in different sizes from 5 to 20 μm diameter (Fig. 10). Three types of primary fluid inclusions (FI) were identified in apatite type-II. The fluid inclusions differ in their homogenization temperature (TH, i.e. the temperature at which the gas and liquid phases in an aqueous inclusion become homogeneous), density and salinity as listed below: FI-type 1: The most abundant type are two-phase fluid inclusions (Fig. 11A and B) consisting of both, a vapor-dominated phase with minor liquid (V + L) and a liquid-dominated phase with minor vapor (L + V). In the latter FI, the homogenization process occurred at low temperatures (TH = 109–187 °C). The density of these fluid inclusions varied between 0.98 and 1.01 (g/cm3) indicating low salinity (5.31–13.73 wt % NaCl eq.; Table 8). FI-type 2: This type 2 inclusions are mono-phase gas inclusions (V; Fig. 11 C). FI-Type 3: These inclusions are three-phase fluid inclusions (L + V + S) containing solid phases of halite and these are of the least abundant FI type (Fig. 11 D). In contrast to the two-phase fluid

(0.04–0.48 wt %), CaO (0.01–0.32 wt %), MnO (0.01–0.03 wt %) and Cr2O3 (0.01–0.04 wt %). 4.2. Fluid inclusions in apatite In general, fluid inclusions occur in apatites from a wide variety of environments (e.g. magmatic and hydrothermal; Tornos et al., 2016). The Hormuz Island apatites type-I are very small in size and therefore contain no suitable fluid inclusion for studying. The apatite type-II megacrysts are highly transparent and in their central part, host many primary fluid inclusions. Minor secondary fluid inclusions are mostly small in size (≥5 μm) (classified based on Roedder, 1984). Towards the rim, the type-II apatites contain large numbers of magnetite inclusions but with no suitable fluid inclusions for studying. To provide accurate information on the crystallization conditions of the apatite type-II, we studied only those fluid inclusions, which were not affected by secondary cracks. These fluid inclusions display various shapes and these are spindle, round, tubular and rod98

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Table 5 Chemical composition of apatite type-II crystallized in veins within rhyodacite, obtained by ICP-MS analyses.

EU / EU∗ =

EUN (GdN × SmN )

Sample

P2O5 (%wt)

CaO

Si (ppm)

Mn

S

F

Cl

Fe

Ni

Rb

Sr

Zr

La

Ce

Pr

Nd

A1-H A2-H A3-H A4-H A5-H

41.7 41.2 42.0 41.1 41.6

53.0 54.1 53.0 54.8 54.9

370 1288 643 735 1002

155 124 125 112 216

163 151 160 160 338

33432 39184 36235 39129 22912

121 134 217 287 208

954 947 634 765 756

234 176 201 198 179

328 586 255 347 303

297 289 312 354 277

0.59 1.09 0.44 1.12 2.13

2534 3038 2543 2653 2764

7229 7198 6054 6697 6985

954 1032 865 943 946

3730 4055 3263 3658 3712

Sample A1-H A2-H A3-H A4-H A5-H

Sm (ppm) 698 756 644 598 686

Eu 67.1 63.1 56.3 59.1 57.6

Gd 844 897 812 837 802

Tb 124 143 126 120 117

Dy 655 682 605 645 617

Y 534 312 413 638 429

Er 437 468 397 415 402

Tm 57.1 56.9 54.3 54.5 53.2

Yb 363 367 309 303 354

Lu 49.4 50.9 46.0 45.4 44.8

U 2.45 2.39 2.98 1.78 1.95

Th 3.12 3.09 3.75 2.55 2.06

F/Cl 276 292 166 136 110

Eu/Eu* 0.27 0.23 0.24 0.26 0.24

(Ce/Yb)cn 5.15 5.07 5.07 5.72 5.10

∑REE (%wt) 1.83 1.91 1.62 1.77 1.80

inclusions (FI type 1), these L + V + S fluid inclusions show higher densities (1.08–1.15 g/cm3) and salinities (33.77–41.49 wt % NaCl eq.; Table 8). They homogenize at 250–420 °C.

(Belousova et al., 2002), which is of particular interest in case of the apatite type II. Average contents of CaO and P2O5 in apatite type-I (Table 4) and type-II (Table 5) are very similar, corresponding exactly with typical apatite compositions (CaO 53–57 wt % and P2O5 39–44 wt %; Belousova et al., 2002). The microchemical results obtained from SEM (Table 3), EPMA (Table 4) and ICP-MS (Table 5) analyses show that both the apatites of type-I and II are compositionally fluorapatite. Fluorapatite with high F contents > 1 wt %, and a F/Cl ratio > 1 is typical for igneous sources (Chu et al., 2009). The fluorine content in apatite can also be an indicator of the aluminum saturation index (ASI) of the parental magma. Commonly, apatite crystallized from a metaluminous magma contains low amounts of fluorine (1.3–1.5 wt %), whereas those formed from peraluminous magmas contain higher fluorine (2.5–3.6 wt %). The high content of fluorine (2.3–3.9 wt %) in the Hormuz Island apatites may be in accordance with the peraluminous composition of the rocks. In general, the chlorine content in apatite reflects the degree of fractionation of the melts (Chu et al., 2009). Typically, less-fractionated rock types such as carbonatites, lherzolites, and dolerites contain apatite with high amounts of Cl from 0.5 to 2 wt %. Chlorine content in the apatite type-I is on average 0.71 wt % (Table 4); relevant to the crystallization from Hormuz fractionated rhyolitic magma. The apatite type-II shows even lower chlorine contents (av. 0.02 wt %; Table 5), documenting their crystallization from a highly fractionated magma or a hydrothermal source (compare e.g. the widely known hydrothermal Durango apatite, Mexico; Marks et al., 2012; Teiber et al., 2015). Especially the Sr contents of apatite can be used as an indicator to distinguish between apatites crystalized from Ie, Se and, A-type granite suites (Chu et al., 2009). Apatites from I-type granites may contain up to 330 ppm Sr and those from S-type granites contain commonly less than 100 ppm Sr (mostly ∼50 ppm; Chu et al., 2009). The Sr contents of apatite type-II vary between 277 and 354 ppm and it is therefore assumed to have crystallized from an I-type granitic magma. Sha and Chappell (1999) demonstrated that apatites from Itype granites contain less Mn (mostly < 900 ppm) and Fe (< 2100 ppm) than apatites from S-type granites (> 910 ppm Mn and mostly > 2000 ppm Fe). Mn and Fe contents of apatite type-II range from 112 to 216 ppm and 634–954 ppm respectively (Table 5), and therefore, the origin of these apatites is also related to an I-type granitic magma. Zircon is an important accessory mineral in both rocks, the Hormuz Island rhyolites and rhyodacites. The low amounts of Zr in apatite typeII (1.07 ppm) may indicate a magma depleted in Zr during apatite crystallization. U contents in apatites commonly vary from 10 to 100 ppm, (Belousova et al., 2002; Chu et al., 2009). The low concentration of U in Hormuz apatites (av. 2.31 ppm) may also be

5. Discussion 5.1. Geochemistry of the rhyolites and rhyodacites Based on their composition, the rhyolitic and rhyodacitic rocks are classified as peraluminous calc-alkaline rocks. Their compositions plot in the Th/Ta vs. Yb diagram in the active continental margin field (Fig. 12 A, Schandl and Gorton, 2002). Based on the Nb vs. Zr diagram (Fig. 12 B, after Thieblemont and Tegyey, 1994), these rocks crystallized from subduction-related calc-alkaline magmas. Furthermore, the rhyolites and rhyodacites show a gentle negative slope from LREE to HREE, with a low Eu depletion, but are not depleted in Nd in their chondrite-normalized REE patterns (Fig. 13 A). Accordingly they are interpreted as I-type orogenic rocks related to a volcanic arc settings (Faramarzi, 2015; Faramarzi et al., 2015a, b; Faramarzi et al., 2017). The magnesian nature of the Hormuz rhyolites, their zircon saturation temperatures, and the geochemical results obtained from selected minerals such as biotite and zircon, all exclude an origin from A-type magmatism (compare Faramarzi et al., 2017). Zircon crystals obtained from these rhyolites yielded an UePb age of 558 ± 7 Ma (Faramarzi, 2015; Faramarzi et al., 2015a, b; Faramarzi et al., 2017). As mentioned above, the rhyolitic and rhyodacitic rocks show a close relationship in composition and genetic aspects and a similar formation age of the rhyodacites can be assumed. 5.2. Apatite geochemistry The occurrence of apatite type-I in the groundmass of the Hormuz rhyolites (see Fig. 3A and B) and as inclusions in biotites (see Fig. 3C and D) clearly demonstrates that the type-I apatite formed as a primary magmatic mineral, which crystallized during an early magmatic phase. The occurrence of apatite type-I as inclusions in hornblende (see Fig. 5 A) and in feldspar (see Fig. 5 B; Table 3) in rhyodacitic rocks points also to its crystallization from a melt. The high abundance of magmatic apatite in these rocks may be related to the I-type nature of the Hormuz rhyolites and rhyodacites (Faramarzi, 2015; Faramarzi et al., 2015a, b; Faramarzi et al., 2017). Naturally, early magmatic apatite is common in the I-type granites but is less common in S-type and even rare in A-type granites (Broska et al., 2004). In general, the composition of apatite is linked to the chemical composition of the parental magma. Therefore it can help to understand the evolution of the parental magma at the time of its crystallization 99

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Fig. 8. A) Contorted flow layering in massive magnetite ore bodies of Hormuz Island; B) Magnetite scoria scattered in ferruginous ring; C) Ash-like crystalline hematite showing vesicular textures with open vesicles; D) The strongly brecciated magnetite dyke crosscutting the ferruginous ring; E) Strongly altered and fractured rhyolite, cemented by magnetite; F) The ferruginous ring, which consists of angular brecciated fragments of the country rocks cemented by iron oxides; G) Microphotograph of the matrix of the ferruginous ring, showing magnetite, hematite, quartz, chlorite, sericite, and halite in XPL; H) Unconsolidated and laminated fine-grained blocks of sandy magnetite and hematite scattered within the ferruginous ring.

apatite type-II (av. 2.91 ppm) may confirm a genetic relationship to the rhyodacitic magmas. In general, REE can substitute Ca in apatite (e.g. Coulson and Chambers, 1996) and in apatites derived from different sources contain different amounts of REE and, as a result, may show different chondritenormalized trace-element patterns (Belousova et al., 2002). The REE patterns of apatites are generally linked to the bulk REE patterns of their parental magma, but apatite commonly contains higher REE concentrations compared to their source rocks. The total REE content of apatite type-II from Hormuz Island ranges from 1.62 to 1.93 wt % (Table 5). The total REE content in rhyolites and rhyodacites ranges from 17.4 to 241 ppm and 141.7–249.1 ppm respectively (Table 2). The similar REE patterns of the Hormuz Island apatite type-II and their

attributed to zircon crystallization before and/or concurrently with apatite type-II in the parental magma. Therefore, it is possible to assume that apatite type-II was formed after zircon crystallization from the rhyodacitic magma. This implicates that the Th content of apatite type-II should be much lower than that of normal apatite (1–2000 ppm, Belousova et al., 2002; Chu et al., 2009) and monazite should be a common accessory mineral. Zircon is the only mineral, which has a much higher preference for U than Th (Chu et al., 2009), and after zircon crystallization, the residual high amounts of Th tend to partition into the monazite. Monazite was observed as single-crystal minerals in the Hormuz Island rhyolites and rhyodacites, as well as within the apatite rich veins. Furthermore, monazite occurs as inclusions within apatite type-I (see Fig. 6 D). However, the low amounts of Th in the 100

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Fig. 9. A) Alternating bands of hematite and evaporite minerals; B) Quasi “bullet-shaped” and subrounded dropstones in banded jaspilitic hematite, after Atapour and Aftabi (2017); C) Iron oxide ignimbrite from Durango deposits, Mexico, after Mungall et al. (2012); D) Mega-crystals of hematite; E) BSE image from magnetite coexisting with apatite type-II which showing exsolution of ilmenite; F) Iron oxide mineralization as specularite in hand specimen; G) BSE image from tabular specular hematite crystals; H) BSE image of coherent fragments of red soil showing hematite, sericite, and quartz. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Table 6 Chemical composition of magnetites coexisting with apatite type-II analyzed using EPMA. Analysis point

FeO

MgO

Al2O3

SiO2

Na2O

K2O

CaO

Ti2O

Cr2O3

MnO

V2O3

NiO

ZnO

Total

Mt-1 Mt-2 Mt-3 Mt-4 Mt-5 Mt-6 Mt-7

93.3 91.6 92.2 91.8 92.8 94.6 94.1

0.01 0.02 0.01 0.01 0.01 0.01 0.04

0.13 0.16 0.10 0.05 0.06 0.01 0.04

0.41 0.04 0.09 0.11 0.11 0.23 0.48

0.00 0.00 0.03 0.00 0.00 0.00 0.01

0.07 0.01 0.01 0.01 0.04 0.16 0.17

0.15 0.22 0.21 0.25 0.32 0.03 0.01

1.99 4.02 3.04 3.09 0.98 0.08 0.03

0.01 0.04 0.01 0.01 0.01 0.01 0.01

0.02 0.01 0.03 0.03 0.01 0.01 0.01

0.27 0.45 0.37 0.39 0.12 0.45 0.38

0.04 0.06 0.05 0.05 0.04 0.02 0.04

0.02 0.02 0.01 0.03 0.01 0.02 0.02

96.4 96.6 96.2 95.8 94.5 95.6 95.3

101

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Table 7 Chemical composition of banded iron (BI) and red soil (RS) obtained by ICP-MS analyses. Samples (%wt)

SiO2

Al2O3

Fe2O3

MnO

MgO

CaO

Na2O

K2O

TiO2

P2O5

L.O.I.

Total

RS 1 RS 2 RS 3 BI 1 BI 2 BI 3

15.7 15.7 15.7 15.7 15.7 6.14

2.13 1.94 3.22 0.62 0.58 0.82

71.3 72.1 74.8 74.9 73.5 63.3

0.23 0.15 0.02 0.03 0.3 0.04

0.78 0.34 0.53 0.02 0.98 1.64

0.26 0.38 0.41 0.23 0.52 17.2

1.54 1.37 1.32 0.54 0.69 0.94

1.02 0.84 1.11 0.67 0.93 0.75

0.08 0.08 0.06 0.05 0.04 0.05

0.29 0.43 0.12 0.07 0.06 0.22

5.8 4.22 2.54 1.34 3.12 8.32

99.0 99.1 99.6 98.6 99.9 99.5

Samples (ppm) RS 1 RS 2 RS 3 BI 1 BI 2 BI 3

Cl 7983 8354 8023 6983 7412 415

F 259 474 389 165 189 53

V 23.1 22.8 25.9 45.2 38.9 56.1

Co 1.8 1.92 2.98 2.18 3.02 1.78

Ni 4.43 5.12 1.54 5.63 6.77 8.22

Cu 12.2 10.4 13.0 73.3 65.1 12.4

Zn 11.3 9.84 12.1 12.7 24.2 24.1

Ga 6.13 6.43 5.06 8.12 8.09 6.93

Rb 23.1 26.0 13.9 2.04 7.45 43.1

Sr 512.1 499.3 617.8 301.2 314.9 246.9

Y 9.12 8.93 8.99 12.9 6.74 28.9

Zr 47.1 28.9 44 27.2 21.4 191.0

Samples (ppm) RS 1 RS 2 RS 3 BI 1 BI 2 BI 3

Nb 3.73 4.12 4.18 1.24 1.58 8.23

Mo 3.24 2.09 2.45 21.6 19.8 49.6

Ag 0.21 0.01 0.09 1.02 1.32 0.75

Sn 1.08 2.02 1.43 3.94 4.18 15.0

Ba 896 1120 743 534 389 1286

La 27.1 32.9 25.9 54.1 36.9 190

Ce 30.0 31.8 26.7 57.0 41.1 209

Pr 3.42 2.78 2.63 5.67 5.24 18.9

Nd 5.98 5.06 5.77 5.94 4.76 49.4

Sm 0.93 1.06 0.98 0.75 1.02 7.12

Eu 0.66 0.54 0.62 0.54 0.72 6.66

Gd 1.4 1.54 1.76 1.81 1.93 5.47

Samples (ppm) RS 1 RS 2 RS 3 BI 1 BI 2 BI 3

Tb 0.32 0.34 0.27 0.43 0.71 0.78

Dy 0.57 0.47 0.52 0.78 0.56 21.9

Ho 0.76 0.84 0.68 0.70 0.81 0.93

Er 0.09 0.2 0.24 0.21 0.34 3.01

Tm 0.06 0.09 0.05 0.10 0.08 0.29

Yb 0.21 0.25 0.21 0.12 0.21 2.01

Lu 0.09 0.12 0.11 0.06 0.07 0.21

Hf 0.83 0.92 1.02 1.01 1.05 3.71

Ta 0.44 0.53 0.47 0.56 0.74 0.81

Th 3.82 4.94 3.08 1.21 1.52 10.3

U 2.12 3.76 2.93 1.83 1.30 8.11

Fig. 10. Microphotograph of fluid inclusions hosted in the Hormuz apatite type-II and their different shapes based on the classification of Roedder (1984). A) spindle; B) rounded; C) tubular and D) rod-shaped.

Fig. 11. Microphotograph of fluid inclusions hosted in the apatite type-II and their classification based on the contained phases. A) A two-phase fluid inclusion with high liquid phase (L + V). B) A two-phase fluid inclusion with high vapor phase (V + L). C) A monophase gas fluid inclusion (V). D) A three-phase fluid inclusion (L + V + S) containing solid phases of halite.

peraluminous S-type granites are flat or show upwardly convex shapes and are characterized by negative Eu and Nd anomalies. The slope of the REE pattern reflects the degree of LREE/HREE fractionation in a magma series. Frietsch and Perdahl (1995) have demonstrated that calc-alkaline magmas show a weak to moderate LREE/HREE fractionation, whereas alkaline magmas show a stronger LREE/HREE fractionation. The weak negative slope from LREE to HREE for the Hormuz apatite type-II (Fig. 13 B) may refer to their crystallization from a calc-

rhyodacite host rocks, as well as rhyolites (Fig. 13A and B) suggest that they all have formed from the same parental magma. This pattern shows the gentle negative slope from LREE to HREE with a negative Euanomaly without depletion of Nd (Fig. 13 B), which all confirm their crystallization from peraluminous I-type granitic magmas. The REE patterns of apatites from metaluminous rocks typically show significant negative slopes and are characterized by little or no Eu negative anomaly (Fig. 13 C). In contrast, the REE patterns of apatites from 102

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genetic scenarios are possible: (1) late magmatic fluids were released or exsolved from a magma due to fractionated crystallization, similar to the process described e.g. by Tornos et al., (2016); (2) fluids, derived from an external source, e.g. meteoric or basinal fluids were heated during convection around the intruded magmatic body (Rhodes and Oreskes, 1999); (3) a combination of the aforementioned two processes by formation of an early generation of minerals crystallizing in a magma and a second generation overgrowing the mineral phases due to interaction with external hydrothermal fluids (e.g. Knipping et al., 2015). In the latter case, two generations of fluid inclusions could coexist within a mineral. Using the density and homogenization temperature TH (Shepherd et al., 1985), it is possible to estimate the pressure during the formation of the fluid inclusions. Fig. 15 A shows that two different types of fluid inclusions can be distinguished in the Hormuz apatite type-II. According to the high density and high TH (300–400 °C), the three-phase inclusions (L + V + S) of the Hormuz apatite type-II formed under slightly higher pressures (50–200 bar) compared to the two-phase fluid inclusions (< 50 bar). The salinity and homogenization temperature (TH) of the fluid inclusions can be used to identify various fluid compositions and fluid evolution processes. According to the Wilkinson (2001) diagram, threephase fluid inclusions (L + V + S) are overprinted by heating and depressurization processes (Fig. 15 B). Heating due to depressurization is a common magmatic process, which occurs during magma ascent from depth to the earth's surface. In contrast, two-phase inclusions point to fluid dilution, caused by interaction with surface fluids. The measured salinities and homogenization temperatures in the threephase and two-phase FI are different, indicating different sources of the fluids prevailing during the formation of apatite type-II. As shown in Fig. 15 B, the three phase FI can be related to late magmatic evolution and a second set, presenting the two phase FI, suggests be the result of hydrothermal processes by mixing of magmatic fluid with surface fluids. This becomes clearer when plotting the data in the salinity versus TH diagram of Kesler (2005), also developed to decipher the source of the fluids in inclusions. As shown in Fig. 15 C, the values plot along a line starting in field of the magmatic fluids and ending in the field of basinal hydrothermal fluids. This trend suggests that FI of apatite typeII have a magmatic source but were successively overprinted by hydrothermal processes and fluids.

Table 8 Microthermometric results of the Hormuz Island apatite type-II. Phases

L L L L L L L L L L L

+V+ +V+ +V+ +V+ +V+ +V+ +V+ +V +V +V + V

S S S S S S S

TH total °C

Ts NaCl °C

Tm

ice°C

420 334 270 330 250 307 374 187 164 98 109

296 295 289 235 289 257 340 – – – -

– – – – – – – −9.8 −8 −3.3 −4.8

Salinity (wt% NaCl eq.)

Density (g/ cm3)

37.85 37.78 37.33 33.77 37.33 35.12 41.49 13.73 11.7 5.31 7.53

1.09 1.09 1.11 1.11 1.15 1.1 1.08 0.98 0.99 0.99 1.01

alkaline magma, which is characteristic for convergent plate boundaries (Fig. 13 D). The HREE contents (2762–3063 ppm) in the apatite type-II points also to their crystallization from a peraluminous granitic melt. Commonly, the HREE concentration in apatites from peraluminous granites is higher (400–10,000 ppm) than that of apatites from metaluminous ones (Gd to Lu plus Y: 100–2000 ppm), whereas the LREE content is approximately similar in apatites crystallized from both types of magma (La to Eu: 1000–10,000 ppm; Chu et al., 2009). The relatively low contents of HREE in the Hormuz Island apatite type-II in comparison to typical apatites from peraluminous granites may be caused by the formation of HREE-rich accessory minerals before and/or during apatite crystallization. Minerals concentrating the HREE, e.g. zircon and hornblende, are common in rhyodacites. It is noteworthy that zircon and hornblende are not found in the veins occurring within the rhyodacitic rocks. Belousova et al. (2002) have shown that, in addition to REE patterns, there is a close relationship between apatite composition (Sr, Y, Mn, ∑REE and Eu/Eu*) and the respective source rock type. Therefore, it is possible to distinguish the apatite source rocks. According to the plots of Sr vs. Y, Mn, Eu/Eu* vs. Y, and (Ce/Yb) cn vs. ∑REE, it is conceivable that the Hormuz Island apatite type-II have formed from a source analogous to a granitic magma (Fig. 14 A - D). However, some samples plotting within or closed to the "iron ore" compositional field may be related to the occurrence of type II apatite megacrysts in close association with the brecciated ferruginous ring. 5.3. Apatite microthermometry

5.4. Iron oxides geochemistry

The two different primary fluid inclusion characteristics may provide valuable data to reconstruct the mineralization conditions of apatite type II. Based on chemical composition, temperature, pressure, and salinity of the trapped fluids in the inclusions three different

The geochemistry of iron oxides can indicate the mineral deposit type to which they belong (e.g., Loberg and Horndahl, 1983; Nadoll et al., 2012). Therefore, we used the geochemistry of iron oxides from Hormuz Island not only as a powerful tool to clarifying their Fig. 12. Hormuz rhyolites and rhyodacites plotted in A) the active continental margin field of Schandl and Gorton (Th/Ta vs. Yb, 2002) diagram and B) the subduction-related calc-alkaline field of the Nb vs. Zr diagram after Thieblemont and Tegyey (1994). The Nb and Zr contents are normalized based on primitive mantle (after McDonough and Sun, 1995).

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Fig. 13. Chondrite-normalized REE patterns of A) Hormuz Island rhyodacites and rhyolites; B) Hormuz Island apatite type-II; C) in comparison apatites from metaluminous, I-type and S-type peraluminous granites (after Chu et al., 2009) and D) apatites from calc-alkaline and alkaline rocks (after Frietsch and Perdahl, 1995). The chondrite REE values are those from Boynton (1984).

Fig. 14. Trace element discrimination plots for apatite type-II from Hormuz Island. A) Sr vs. Y. B) Sr vs. Mn. C) (Ce/Yb)cn vs. ∑REE and D) Y vs. Eu/Eu* (after Belousova et al., 2002).

Kiruna-type iron ores; see Loberg and Horndahl, 1983, Fig. 16A–C), the analytical results obtained from banded iron stones and red soil does not suggest any magmatic affinity. Instead, the banded iron stone and the red soil show geochemical similarities with typical sedimentary Banded Iron Formations (BIF; Fig. 16A–C). The alternating bands of hematite and salt minerals in Hormuz

relationship with type II apatite megacrysts but also as a petrogenetic indicator. Iron oxides from Hormuz Island show different geochemical characteristics. Whereas the ferride and trace element geochemistry of magnetite coexisting with apatite type-II confirm their geochemical similarity with magmatic and volcano-sedimentary iron ores (e.g.

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Fig. 15. The Hormuz apatite type-II comprise two different fluid inclusion groups according to A) TH vs density (Shepherd et al., 1985); B) TH vs. Salinity (Wilkinson, 2001) and C) salinity vs. TH (modified after Kesler, 2005).

and magnetite not only in the rhyodacites but also their abundance in the surrounding ferruginous ring (see Fig. 2 B) may indicate an interaction with hydrothermal fluids. Additionally, the geochemistry of the magnetites from Hormuz Island shows both magmatic and hydrothermal affinities (Fig. 16 D and E), which may be related to a transitional cooling trend from purely magmatic conditions to magmatichydrothermal conditions, following the ascent from depth to surface. Such a model is also in agreement with similar processes that have been proposed for the formation of many massive iron deposits worldwide by a synergistic combination of common magmatic processes enhanced during the evolution of caldera-related explosive volcanic systems (e.g. Ovalle et al., 2018; Lyons, 1988; Alva-Valdivia et al., 2001). Hydrothermal activity has been also reported from the other salt domes of the Hormuz Formation (South Iran), where hot fluids led to the formation of minerals like magnesioriebeckite, garnet, and epidote (Mortazavi et al., 2017). It is thus reasonable to assume that fluid mixing and complex hydrothermal processes, e.g. the combination of igneous and magmatic-hydrothermal processes (Broughm et al., 2017) may have led to the formation of the iron ores at Hormuz Island. The characteristics of this iron ore deposit are similar to that of the Kiruna-type magnetiteapatite ores (Faramarzi, 2015). Similarly, at Chador-Malu and Choghart (Bafq District, Central Iran), the circulation of high-temperature FeeP fluids, derived during the late-stage of magmatism and subsequent hydrothermal activities led to formation of a Kiruna-type magnetiteapatite ore deposit (Sabet-Mobarhan-Talab et al., 2015; Williams and Houshmand-Zadeh, 1996). Additionally, the occurrence of specular hematite along the south coast of Hormuz Island, where the neighboring volcanic rocks consist of rhyolitic, may point to the role of magmatic fumaroles. Gay-Lussac (1823) has shown that FeCl3 vapor, induced by felsic magmatism, in contact with water vapor at a high temperature, can lead to the formation of fumarolic specular hematite deposits. Such vapor reactions are considered to be responsible for the formation of the ash-like

Island are not consistent with the normal evaporation sequence of evaporites. Commonly, due to the lower solubility of hematite compared to calcite or salt minerals, hematite precipitates before or along with calcite without precipitating sequentially with anhydride or halite. Consequently, the alternating bands of hematite and salt minerals are probably related to synchronous seawater evaporation associated with exhalative hydrothermal pulses of mineralizing solutions and successive periods of submarine felsic volcanism. To discriminate between magmatic and hydrothermal magnetite, Knipping et al. (2015) proposed a discrimination diagram based on V vs. Ti concentrations. Although all analyzed magnetites from the present study lie within the magmatic field of the Knipping et al. (2015) diagram, two samples may refer to a hydrothermal process because they plot in the magmatic and hydrothermal overlapping area (see Fig. 16 D). Based on the discrimination diagram proposed by Dare et al. (2014), it is also possible to distinguish magmatic magnetites from hydrothermal ones using Ti and Ni/Cr concentrations (Fig. 16 E). The magnetites from Hormuz Island plot in both the magmatic and hydrothermal fields and this may indicate that they formed due to a combination of igneous and magmatic-hydrothermal processes. 5.5. Hydrothermal activity Generally, fluid mixing can play a critical role in the formation of hydrothermal minerals (Zhai et al., 2013; Jazi et al., 2017). Minerals like apatite, magnetite, fluorite, or monazite, can crystallize during late magmatic hydrothermal activities. The strong alteration of the rhyodacites including mineral such as albite, quartz, and fine-crystalline mica, together with the occurrence of magnetite inclusions in the rims of apatite megacrysts may also point to the post-magmatic interaction with hydrothermal fluids. Based on the petrography and geochemistry of the veins within the rhyodacitic rocks, the hydrothermal fluids were enriched in P, F, Na, Ca, Si, and REE. The crystallization of hematite 105

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Fig. 16. Iron oxide discrimination diagram by Loberg and Horndahl (1983) to distinguish various deposit types; A) based on V (ppm) vs. Ni (ppm); B) based on V (ppm) vs. Ti (ppm) and C) based on V/Ti vs. Ni/Ti with samples from this study plotted; D) Magnetite discrimination diagram based on the V vs. Ti concentrations proposed by Knipping et al. (2015) to distinguish magmatic and hydrothermal settings of the Hormuz Island magnetite; E) Magnetite plot on the Ti vs. Ni/Cr diagram proposed by Dare et al. (2014) to discriminate between magmatic and hydrothermal environments for magnetite formation.

Th, Sr, Mn, Fe, and the REE contents, the parental magma was peraluminous and calc-alkaline. Therefore, one common parental magma with a Late Neoproterozoic to Early Cambrian age (558 ± 7 Ma; Faramarzi et al., 2015a,b) is suggested as being responsible for the crystallization of both types of apatite. This conclusion differs from the fission track age of 55.4 ± 2.6 Ma for the Hormuz Island apatite type-II (Hurford et al., 1984), which has already been mentioned by some authors (e.g. Ghazban and Al-Aasm, 2010; Atapour and Aftabi, 2017) as crystallization time of apatite. Based on Hurford et al. (1984), the age of 55.4 ± 2.6 Ma does obviously not reflect the crystallization time of apatite and was possibly caused by later processes. Our microthermometric results obtained from primary fluid inclusions, however, indicate a more complex evolution of the apatite typeII. The three-phase fluid inclusions confirm a magmatic origin of the fluids trapped during the early crystallization stage. The low pressure, salinity, and homogenization temperatures (TH) of the two-phase fluid inclusions, however, indicate the interaction with external, non-

crystalline hematite in the apatite-bearing iron deposits of the Cerro de Mercado, Durango-Mexico (Lyons, 1988), which shows great similarities to the rocks at Hormuz Island from a minerogenetic point of view. 6. Conclusions Petrographic and geochemical results obtained from SEM, EPMA and ICP-MS analyses reveal that the apatites from the Hormuz Island rhyolites and rhydacites (type-I) as well as the single-crystal apatites (type-II) crystallized in veins within the rhyodacitic rocks expose very similar characteristics. Apatite type-I is a primary fluorapatite, which has crystallized during an early magmatic phase from a peraluminous calc-alkaline magma. The magma was compositionally classified as an I-type granite, which formed in a volcanic arc setting at an active continental margin. Similarly, apatite type-II is also a fluorapatite. According to the Sr, Y, Mn, Cl, ∑REE, and Eu/Eu* characteristics, apatite type-II formed from an I-type granitoid magma. Based on the F, 106

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magmatic fluids. The coexistence of two generations of fluid inclusions in magmatic apatite crystals can only occur when an early generation of magmatic apatite has been overprinted by subsequent hydrothermal fluids. The salinity and TH of the fluid inclusions indicate the mixing of magmatic and basinal fluids during the growth of apatite type-II. In addition to the felsic magmatism, a volatile-rich, iron oxide magmatism occurred at Hormuz Island. The well-preserved volcanic structures and textures in the massive iron-oxide bodies indicate crystallization from this iron oxide magma. Additionally, all of the available analytical data are consistent with a magmatic origin for the island's massive iron deposits. The close relationship between felsic and iron oxide magmatism in Hormuz Island is consistent with the magmatic model involving immiscibility between silicate and iron oxide-rich melts, which have been proposed for the genesis of Kiruna type deposits (Lyons, 1988). The results also confirm that the nearby magnetite-apatite veins as well as the mega-crystals of hematite and specularite were formed at high temperature from magmatic-hydrothermal fluids, released from the crystallizing magma. However, the occurrence of banded iron stones, red soil and the alternating bands of hematite with evaporite minerals could be the result of seawater-rhyolite interactions by circulating exhalative hydrothermal fluids.

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Acknowledgment We gratefully acknowledge Dr. Sadraddin Amini (department of Earth, Planetary, and Space Sciences of UCLA) for providing EPMA analyses, Prof. Christoph Gauert for providing XRF analyses (the University of the Free State of South Africa) and Sabine Walther (Martin Luther University Halle-Wittenberg, Germany) for helping with the SEM analyses. We are also grateful to Dr. Abdolrahim Houshmandzadeh for constructive suggestions. The Payame Noor University is appreciated for financially supporting this project. References Allen, P.A., 2007. The Huqf Supergroup of Oman: basin development and context for Neoproterozoic glaciation. Earth Sci. Rev. 84, 139–185. Alva-Valdivia, L.M., Goguitchaichvili, A., Urrutia-Fucugauchi, J., Caballero-Miranda, C., Vivallo, W., 2001. Rock-magnetism and ore microscopy of the magnetite-apatite ore deposit from Cerro de Mercado, Mexico. Earth Planets Space 53, 181–192. Atapour, H., Aftabi, A., 2017a. Comments on “geochronology and geochemistry of rhyolites from Hormuz Island, southern Iran: a new Cadomian arc magmatism in the Hormuz Formationˮby N. S. Faramarzi, S. Amini, A. K. Schmitt, J. Hassanzadeh, G. Borg, K. McKeegan, S. M. H. Razavi, S. M.Mortazavi, Lithos, Sep. 2015, V.236-237, P.203-211: a missing link of Ediacaran A-type rhyolitic volcanism associated with glaciogenic banded iron salt formation (BISF). Lithos 284–285, 779–782. Atapour, H., Aftabi, A., 2017b. The possible synglaciogenic Ediacaran hematitic banded iron salt formation (BISF) at Hormuz Island, southern Iran: implications for a new style of exhalative hydrothermal iron-salt system. Ore Geol. Rev. 89, 70–95. Belousova, E.A., Walters, S., Griffin, W.L., O'Reilly, S.Y., Fisher, N.I., 2002. Apatite as an indicator mineral for mineral exploration: trace-element compositions and their relationship to host rock type. J. Geochem. Explor. 76, 45–69. Bodnar, R.J., 2003. Introduction to fluid inclusions. In: In: Samson, I., Anderson, A., Marshall, D. (Eds.), Fluid Inclusion-Analysis and Interpretation, vol. 32. pp. 1–9 Mineralogical Association of Canada, Short Course Series. Bosak, P., Jaros, J., Spudil, J., Sulovsky, P., Vaclavek, V., 1998. Salt plugs in the Eastern Zagros, Iran: results of regional geological reconnaissance. Geolines, Institute of Geology, Academy of Sciences of the Czech Republic 7, 1–178. Boynton, W.V., 1984. Geochemistry of the rare earth elements. Meteorite studies. In: Henderson, P. (Ed.), Rare Earth Element Geochemistry. Elsevier, pp. 63–114. Broska, I., Williams, C.T., Uher, P., Konečný, P., Leichmann, J., 2004. The geochemistry of phosphorus in different granite suites of the Western Carpathians, Slovakia: the role of apatite and P-bearing feldspar. Chem. Geol. 205, 1–15. Broughm, S.G., Hanchar, J.M., Tornos, F., Westhues, A., Attersley, S., 2017. Mineral chemistry of magnetite from magnetite-apatite mineralization and their host rocks: examples from Kiruna, Sweden, and El Laco, Chile. Miner. Deposita 52 (8), 1223–1244. Brown, P.E., Lamb, W.M., 1989. P-V-T properties of fluids in the system CO2-H2O-NaCl: new graphical presentations and implication for fluid inclusions studies. Geochem. Cosmochim. Acta 53, 1209–1221. Cao, M., Li, G., Qin, K., Seitmuratova, E.Y., Liu, Y., 2012. Major and trace element characteristics of apatite in granitoids from central Kazakhstan: implications for petrogenesis and mineralization. Resour. Geol. 62, 63–83. Chu, M.F., Wang, K.L., Griffin, W.L., Chung, S.L., O'Reilly, S.Y., Pearson, N.J., Lizuka, Y.,

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