Geochemistry of late Archaean metagreywackes from the Western Dharwar Craton, South India: Implications for provenance and nature of the Late Archaean crust

Gondwana Research 15 (2009) 178–187

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Gondwana Research j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / g r

Geochemistry of late Archaean metagreywackes from the Western Dharwar Craton, South India: Implications for provenance and nature of the Late Archaean crust V.S. Hegde a,⁎, V.C. Chavadi b a b

S.D.M. College of Engg. & Tech., Dharwad-580 002, India Department of Geology, K.U. Dharwad-580 003, India

a r t i c l e

i n f o

Article history: Received 25 May 2007 Received in revised form 16 September 2008 Accepted 29 September 2008 Available online 17 October 2008 Keywords: Western Dharwar Craton Late Archaean metagreywackes Rare earth elements Provenance Tectonic setting

a b s t r a c t Late Archaean metagreywackes of the Ranibennur Formation, Dharwar Supergroup, in the Dharwar–Shimoga schist belt of the Western Dharwar Craton (WDC) are texturally and mineralogically immature of the quartz-intermediate type. The SiO2 content in them ranges from 60.58 to 65.26 wt.%. Chemical Index of weathering (CIW) values varies between 50 and 65. 4 indicating a low degree of chemical alteration of the provenance rocks. A high degree of correlation between K2O and Al2O3 (r=−0.73) and low Rb/Sr ratios also suggest a low degree of alteration of provenance rocks. Abundances of transition group elements (Cr=118–221; N=89–154; V=89–192 and Sc=11– 16 ppm) as well Zr (132–191 ppm) suggest a mixed mafic–felsic provenance for the metagreywackes. Low HREE and Y content, and low Tb/Yb ratios (0.23–0.41) suggest the presence of tonalite as an important component in the provenance areas. Values of Eu/Eu⁎(0.78) and Th/Sc (0.55) suggest that the granodioritic upper crust had evolved prior to serving as the provenance. Mixing calculations suggest 50–55 vol.% tonalite, 20–25 vol.% granite, 18–20 vol.% basalt and ~5 vol.% komatiite composition for the provenance. Geochemical characteristics of the Ranibennur metagreywackes suggest that sedimentary basin formed in the vicinity of a magmatic arc in a continental island arc setting, and the detritus were shed from the arc rock. © 2008 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

1. Introduction Fine-grained clastic sedimentary rocks serve as representative samples of provenance and hence are useful to study average composition of the upper crust. Petrography and chemical compositions of clastic sedimentary rocks, especially greywackes (McLennan, 1984; Dickinson, 1985; Taylor and McLennan, 1985; McLennan et al., 1990, 1993; Camire et al., 1993), have been used to understand provenance and evolution of the Archaean crust. Archaean crust in the Dharwar Craton showed evolution of sedimentary basins from quartzpebble conglomerate and quartz arenite to dominantly turbidite sequence at the top (Srinivasan and Naqvi, 1990). Naqvi et al. (1988), based on the petrography and major and trace element geochemistry of the late Archaean metagreywackes from Dharwar Carton, proposed a provenance made up of 70 vol.% tonalitic gneiss, 20 vol.% maficultramafic rocks and 10 vol.% sediments. However, this provenance composition is inadequate to explain many geochemical characteristics, in particular, the negative Eu anomaly. Naqvi et al. (1988) reported that chemical fractionation by sedimentary processes between greywackes and interbedded phyllite (originally shale) played a significant role in determining the chemical composition of the greywackes. However, Srinivasan et al. (1992) observed that Eu anomalies in different layers of the Bouma cycle do not show any ⁎ Corresponding author. E-mail address: [email protected] (V.S. Hegde).

strong dependence on grain size. In recent years abundant data, particularly on Archaean granitoids of 3.0 Ga are available (c.f. Meen et al., 1992). This paper attempts to refine the models for provenance proposed by Naqvi et al. (1988) in the light of new data from the late Archaean metagreywackes of the Ranibennur Formation. The studied metagreywacke–argillite suite constitutes the Ranibennur Formation of the Dharwar Supergroup (Harinadha Babu et al., 1981). It occurs over a large area of the Dharwar-Shimoga schist belt (Fig. 1A). The stratigraphic position within the Dharwar Supergroup is given in Table 1. Metagreywackes form part of the Chitradurga Group. The Chitradurga Group commences with basal polymictic conglomerate, chlorite schist, cross-bedded to rippled quartzite and subordinate basic volcanic rocks. The present investigation is confined to the study of metagreywackes exposed to the north of the Honnali Gneiss, which constitutes the basement to the Dharwar Supergroup. The whole rock Rb–Sr isochron age of the Honnalli gneiss is 3035 Ma (Dhana Raju et al., 1983). 2. Methodology Petrographic observations are based on thin sections from 50 representative fresh metagreywacke samples collected from quarry faces. Selected samples were pulverized to ~ 300 meshes in an agate mortar. A portion of the homogenized powder was used for chemical analysis. A dissolution technique (Thomson and Walsh, 1989) was adopted for sample preparation and U.S.G.S rock standards were used

1342-937X/$ – see front matter © 2008 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.gr.2008.09.006

V.S. Hegde, V.C. Chavadi / Gondwana Research 15 (2009) 178–187

as reference materials. Major elements were determined in 21 samples using a double beam Hitachi 902 Atomic Absorption Spectrophotometer at the Karnatak University Scientific Instrumentation Center, Dharwad. CO2 and H2O were determined by the method after Hughes and Hannacker (1978). Eight of the metagreywacke samples were analyzed for trace and rare earth elements by ICP-MS at the National Geophysical Research Institute, Hyderabad. The routine

179

precision for major elements is better than 1%; for trace elements it is better than 5%. 3. Geological setting and petrography The Ranibennur metagreywackes generally occur as ~ 1 m thick beds. They show graded bedding and comprise the A and B divisions of

Fig. 1. A Regional geological map of the Shimoga basin showing the area of the present investigation (source Swami Nath and Ramakrishnan, 1981). Fig. 1B Simplified geological map of the Ranibennur area (mapped by V.S.Hegde).

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Fig. 1 (continued).

the Bouma sequence. The metagreywackes are commonly interstratified with thin (approximately 15–20 cm thick) pelitic beds. Rhythmic inter-banding of banded iron formation on a regional scale is a common feature in the metagreywackes of the study area (Fig. 1B). The metagreywackes show syn-form and anti-form structures with axis trending Northwest–Southeast. The rocks locally display convolute bedding and lamination (Chavadi and Hegde, 1988). The greywackes are metamorphosed to lower green-schist facies of metamorphism and hence referred to as metagreywackes. However metamorphic fabric is not noticeable in hand specimen. The metagreywackes have a poorly sorted texture consisting of sand-sized (~ 0.65 mm) quartz, plagioclase, K-feldspar and fragments of metasedimentary rocks (~ 2.5 mm) set in a finer-grained (b0.03 mm) matrix (25.3–38.5 vol.%) consisting of an intimate intergrowth of chlorite, sericite and biotite. Part of the matrix also consists of silt-sized quartz and feldspar. The framework quartz grains are both mono-crystalline and polycrystalline, and plagioclase is sodic (An 10–25). K-feldspar is mostly perthitic. The rock fragments are angular and include commonly chert, quartzite and slate/phyllite. Carbonate (mostly dolomite) is a secondary phase, which replaces plagioclase and mica in the matrix. Common heavy minerals are zircon, titanite, apatite and rutile. Opaque minerals include pyrite and ilmenite and its alteration product leucoxene, both of which occur as irregular masses in the matrix. Pyrite occurs as euhedral crystals replacing other minerals, suggesting a late-stage origin.

Crook (1974) categorized 3 modes of provenance based on the quartz content: quartz-poor greywackes (b15 vol.% quartz) of volcanic provenance, quartz-rich greywackes (N65 vol.% quartz) of sedimentary provenance, and quartz-intermediate greywackes (15–65 vol.% quartz) of mixed provenance. The modal quartz contents in the Ranibennur metagreywacke (31–42 vol.%) fall in the range of the quartz-intermediate greywackes, and agree with the observation of McLennan (1984) that most Archaean greywackes belong to the quartz-intermediate type. Q–F–L plots for the metagreywackes show that they are akin to greywackes of the recycled orogen (c.f. Dickinson et al., 1983) (Fig. 2). 4. Major element composition In general, the Ranibennur metagreywackes are sodic (Na2O/K2O N 1) in composition. SiO2 ranges from 60.6 to 65.3 wt.% (Table 2) and Al2O3 ranges from 12.4 to 14.8 wt.%. The chemical indices of weathering (CIW) of the metagreywackes range from 54.4 to 65.4, indicating a low degree of chemical weathering. There is a strong negative Pearson correlation between Al2O3 and K2O (r = −0.73), which can be cited as evidence of weak chemical weathering because, in many basalts and granites, the contents of Al and K are negatively correlated (Plank and Langmuir, 1988; Maniar and Piccoli, 1989). SiO2 values show a pronounced inverse

Table 1 Stratigraphy of the Dharwar Supergroup (in Dharwar–Shimoga Belt) Ranibennur formation Chitradurga group

Unconformity Bababudan group

Metagreywackes argillite suite ~ 8800 m thick

Medur formation

Acidic and acidic intermediate volcanics and subordinate chemical sediments. ~ 600 m Joldhal formation Limestone and dolomites, banded manganese formation and banded iron formation Jandimatti formation Polymictic conglomerate, current bedded lithic arenite, quartz sericite schist/phyllite ~ 1000 m (Not divided into formation)

Unconformity 2900–3360 Ma Basement rocks

Quartz pebble conglomerate, quartzite, phyllite, banded ironstone with acidic and basic volcanic rocks ~ 1200 m TTG suite of rocks

After Swami Nath and Ramakrishnan, 1981.

Fig. 2. Q–F–L ternary plot for the metagreywackes of the Ranibennur area (Field boundaries after Dickinson et al., 1983).

V.S. Hegde, V.C. Chavadi / Gondwana Research 15 (2009) 178–187

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Table 2 Modal compositions of the Ranibennur metagreywackes Sample

X1

Quartz Feldspar Carbonate Matrix Lithic fragments Others Q F L L/F

36.20 31.80 37.60 39.20 12.00 11.20 14.40 14.50 10.20 10.60 7.20 5.70 35.10 32.70 33.30 36.60 4.70 4.70 5.90 2.10 1.80 9.00 1.60 1.50 68.40 66.70 64.90 69.70 22.70 23.40 24.90 26.50 8.80 9.90 10.20 3.70 0.40 0.40 0.40 0.10

X2

X10

X-13

X-18

X-26

R-7

R-12

R-35

R-47

A-7

A-13

A-19

A-26

A-33

G-6

G-7

G-9

39.70 39.80 35.40 34.30 40.00 41.00 38.80 39.00 42.00 37.60 36.00 41.00 38.00 41.50 13.90 11.20 11.40 12.00 11.80 11.60 15.40 11.40 11.80 12.00 14.50 14.50 12.20 11.00 5.00 7.00 7.40 8.80 9.50 8.50 6.40 7.60 6.20 6.80 7.00 7.00 6.80 7.00 35.60 36.20 38.50 35.20 32.40 29.80 25.30 29.30 36.50 35.00 32.60 29.00 3.00 32.50 3.70 4.50 4.30 5.80 3.40 6.30 6.70 5.90 2.50 3.60 5.40 5.50 7.00 4.00 2.00 1.30 3.0 3.90 2.90 2.80 7.40 6.80 1.00 5.00 4.50 3.00 6.00 4.00 69.30 71.70 69.20 65.80 72.00 19.60 63.70 69.30 74.60 70.60 64.40 67.00 66.00 73.00 24.20 20.20 22.30 23.00 21.30 19.70 25.30 20.20 21.00 22.50 26.00 23.70 21.00 19.40 6.40 8.10 8.40 11.10 6.10 10.70 11.00 10.50 04.00 6.70 9.60 9.00 12.20 7.00 0.30 0.40 0.40 0.50 0.30 0.50 0.40 0.50 0.20 0.30 0.40 0.40 0.50 0.40

G-10

G-12

G 13

36.50 42.00 42.00 15.00 11.50 11.50 7.40 6.70 8.00 30.40 34.00 28.00 7.00 3.80 5.70 3.70 2.00 4.70 62.40 73.00 70.90 25.60 20.00 19.00 11.90 6.60 7.90 0.50 0.30 0.50

Others include iron oxide, pyrite, titanite, zircon and apatite.

correlation with FeO(t), Al2O3 and Na2O, a moderate correlation with MgO, and a weak correlation with K2O and CaO. This suggests an increase in the quartz content with corresponding decrease in phyllosilicates and feldspars. A positive correlation is observed between SiO2 and P2O5. As both quartz and apatite are detrital, the positive correlation may suggest that P2O5 resides in the sand fraction. FeO (t) shows a moderate positive correlation with MgO. The MgO v/s FeO (t) plot for the Ranibennur metagreywackes (Fig. 3) shows an ironenrichment trend with regard to the MgO–FeO (t) igneous trend line, and hence precludes a significant contribution from basaltic sources. The composition of the Ranibennur metagreywackes suggests that postdepositional metasomatism has not affected them, as indicated by the negative correlation between MgO and Na2O and low values of Mg/K and Na/K (b2.7). Metasomatism produces a large scatter in Mg and Na distribution, resulting in low order or no correlation. According to Legault and Hattori (1994), low values (b4) of Mg/K and Na/K in metagreywackes are characteristic of un-metasomatised rocks. The K/Rb ratios of Ranibennur metagreywackes are consistent with the K/Rb ratios of tonalites (221–225) and basaltic rocks (196) of the WDC (Jayaram et al., 1983; Rama Rao et al., 1991) and absolute values of K2O in the metagreywackes are comparable to the AUCC (Taylor and McLennan, 1985). These features suggest that the Ranibennur metagreywackes have not been modified by K- metasomatism.

The values of Cr and Ni, as well as the ranges of Co, Sc and V abundances (21–30; 11–16 and 89–192 ppm respectively) are close to the average upper crustal composition (Fig. 4). Therefore, a significant contribution from ultramafic/komatiitic sources is unlikely. The abundances of the large ion lithophile elements (LILE) Sr and Rb are high in the Ranibennur metagreywackes (228–733 ppm and 40–94 ppm, respectively) with regard to AUCC (Fig. 4) and suggest a granitic source. The Rb contents are similar to those in tonalites of the WDC, which have Rb contents of 75.7 ± 31.2 ppm (c.f. Jayaram et al., 1983). The abundances of Hf and Zr are high in the Ranibennur metagreywackes, and Zr/Hf is high (42.4) compared to the other Archaean greywackes, which typically show Zr/Hf in the range between 33 and 40. Th/U ratios in the Ranibennur metagreywackes are low (average 3.17) compared to the Th/U ratio of 3.8 for the average Archaean upper crust (Taylor and McLennan, 1985). The Th/U ratios suggest a comparative enrichment of uranium in the metagreywackes. This is indicative of a provenance of K-rich granites, thus corroborating the inferences derived from LILE data. The presence of microcline in the rocks, as well as the occurrence of 3.0 Ga granodiorites at Chikmagalur as part of the Dharwar basement (Chadwick et al., 1985), lends support to our interpretation. 6. REE patterns

5. Trace element composition Cu and Zn are enriched in the metagreywackes and Cu/Zn ratios range between 0.76 and 1.93 (average 0.93), which closely resembles the Cu/Zn ratios of tholeiitic basalts (1.0), high Mg basalts (1.08) (Glikson, 1983) and komatiitic basalts (0.97) (Wilson and Versfeld, 1994). Therefore the presence of these rock types in the source area cannot be totally ruled out. Cr and Ni contents (118 to 221 ppm and 89 to 154 ppm respectively) (Table 3) are comparable with other late Archaean greywackes derived from a mixed provenance (Hofmann et al., 2003; Hofmann, 2005), but low compared to Archaean shales derived from a mafic source (Fedo et al., 1997; Hofmann et al., 2003).

Chondrite-normalized (Sun and McDonough, 1989) rare earth element (REE) patterns of the Ranibennur metagreywackes reveal overall enrichment of light rare earth elements (LREE)(Fig. 5A) and fractionated LREE/HREE patterns (La/Yb = 7.8–24.66). The La contents vary from 54–156 times and Yb 5–13 times the chondrite values (Table 4). A negative Eu anomaly is observed in all the 8 samples analysed (average Eu/Eu⁎ = 0.78). The Ranibennur metagreywackes are slightly depleted in their total REE content when compared with the post-Archaean verage Australian sedimentary rock (Nance and Taylor, 1977) (Fig. 5B), which may be due to the coarser grain size of metagreywackes relative to those of shale because REE are more concentrated in fine-grained clastics than in coarser fractions. 7. Discussion 7.1. Source area weathering

Fig. 3. Plot of FeO(t) vs MgO for the metagreywackes of the Ranibennur area showing iron enrichment.

The composition of clastic sediments is strongly influenced by chemical weathering of source rocks (Sawyer, 1986; Nesbitt et al., 1996), transport in fluvial systems (Johnsson, 1991) and sediment recycling (Nesbitt et al., 1997). Nesbitt et al. (1997) used A–CN–K and quartz-plagioclase –K- feldspar diagrams to illustrate the effects of the degree of weathering of granitic and granodioritic sources on the composition of clastic sediments. In the A–CN–K diagram (Fig. 6), the plot for the Ranibennur metagreywackes corresponds to zones III and IV of Nesbitt et al. (1997), suggesting that the source material is less weathered. Severely weathered sedimentary sequences have

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Table 3 Chemical compositions of metagreywackes of the Ranibennur area (in wt.%) Sample

X-1

X-2

X-10

X-13

SiO2 A12O3 TiO2 FeO(t) MgO K2O Na2O CaO MnO P2O5 LOI(t) Total CIW Na2O/K2O Al2O3/ Na2O SiO2/MgO Na/K Mg/K

61.24 14.23 0.49 9.17 4.34 1.88 4.18 2.26 0.08 0.08 2.00 99.95 56.40 2.22 3.40 14.10 2.00 1.70

60.58 13.60 0.56 10.75 4.57 1.64 3.24 2.08 0.07 0.07 2.83 99.99 59.80 1.97 4.20 13.30 1.70 2.20

61.91 14.69 0.48 8.73 3.42 2.15 4.06 1.82 0.08 0.08 2.57 99.99 59.50 1.88 3.60 19.00 1.70 1.10

62.25 14.84 0.43 9.84 4.05 1.56 3.06 1.55 0.06 0.10 2.24 99.98 65.40 1.96 4.80 15.40 1.80 1.90

X-18

X-26

R-7

R-12

R-35

R-47

A-7

A-13

A-19

A-26

A-33

G-6

G-7

G-9

G-10

G-12

62.26 62.92 61.85 61.18 63.31 64.75 64.81 63.28 65.18 63.52 61.27 64.07 63.41 64.85 61.98 65.26 14.19 13.40 13.94 14.11 13.90 13.53 14.74 13.19 13.81 13.83 14.38 14.27 13.44 12.36 14.81 13.12 0.38 0.43 0.30 0.44 0.38 0.40 0.53 0.52 0.41 0.51 0.50 0.53 0.45 0.46 0.39 0.42 9.46 9.54 8.74 10.00 8.85 7.74 7.59 8.86 7.56 9.13 9.61 8.36 9.18 9.37 8.83 8.04 4.16 4.18 4.31 4.61 4.09 3.91 2.90 4.18 3.41 3.46 4.01 3.15 3.65 4.00 4.55 4.24 1.54 1.77 1.41 1.39 1.38 1.36 1.48 1.58 1.18 1.55 1.27 1.26 1.72 1.11 1.27 1.48 3.96 4.12 4.30 4.09 3.74 3.92 4.06 3.15 3.55 3.53 4.16 4.06 3.39 2.84 3.60 2.78 1.73 1.36 2.51 1.91 2.38 2.08 1.55 2.03 2.22 1.71 2.22 2.20 2.03 1.90 2.18 1.22 0.06 0.06 0.10 0.12 0.03 0.02 0.10 0.10 0.15 0.13 0.13 0.10 0.09 0.10 0.10 0.10 0.11 0.12 0.09 0.10 0.11 0.07 0.10 0.12 0.10 0.15 0.13 0.07 0.11 0.10 0.17 0.07 2.14 2.09 2.44 2.04 1.82 2.21 2.22 2.98 2.42 2.47 2.31 1.92 2.52 2.90 2.11 3.26 99.99 99.99 99.99 99.99 99.99 99.99 99.99 99.99 99.99 99.99 99.99 99.99 99.99 99.99 99.99 99.99 59.40 50.00 54.40 58.00 57.00 57.00 60.80 59.70 58.20 60.80 56.90 57.20 59.10 60.30 60.00 65.90 2.57 2.32 3.04 2.94 2.71 2.88 2.74 1.99 3.00 2.27 3.27 3.22 1.97 2.55 2.83 1.87 3.60 3.20 3.20 3.40 3.70 3.40 3.60 4.20 3.90 3.90 3.50 3.50 4.00 4.40 4.10 4.70 15.00 15.00 14.30 13.30 15.50 16.60 22.30 15.40 19.10 18.30 15.30 20.30 17.40 16.20 13.60 15.40 2.30 2.10 2.70 2.60 2.40 2.60 2.50 1.80 2.70 2.00 3.50 2.90 1.70 2.30 2.50 1.70 2.00 1.70 2.20 2.40 2.10 2.00 1.40 1.90 2.10 1.60 2.30 1.80 1.50 2.60 2.60 2.10 _ Recalculated excluding CaO in carbonate. X average of 21 samples; STD standard deviation.

weathering indices N80 (Fedo et al., 1996; Hofmann et al., 2003) and such severe weathering is related to a CO2-rich atmosphere, an elevated surface temperature and a humid climate (Kasting, 1993; Knauth and Lowe, 2003). A lack of significant chemical weathering is also revealed by the limited variation of Cr/Ni ratios (1.06–1.91; Table 3), indicating no preferential removal of Ni (Ball and Gilkes, 1987). Chemical weathering of the source area produces higher Rb/Sr ratios in sedimentary rocks (Kimberley and Grandstaff, 1986). The Ranibennur metagreywackes, however, show consistently low Rb/Sr ratios (0.11–0.20) compared to the Archaean upper crustal composition (AUCC) (Taylor and McLennan, 1985). The Ranibennur metagreywackes have Al2O3 contents comparable to AUCC, and TiO2 contents are lower than AUCC (Taylor and McLennan, 1985). The low TiO2 contents in the Ranibennur metagreywackes, the weak correlation between Al2O3 and TiO2, and textural and mineralogical immaturities together with Al2O3/Na2O ratios (3.24–4.84) all reveal that the metagreywacke source materials were not highly weathered. It is well known that mineralogical and chemical differentiations are influenced by hydraulic sorting (Nesbitt and Young, 1996) during sediment transportation and deposition. The presence of angular rock fragments and angular grains of quartz suggest that there was a relatively short distance of transportation. As sorting influences REE contents of a rock by fractionation of accessory phases, the effects of

Fig. 4. Average Archaean upper crust (after Taylor and McLennan, 1985) normalized spider plot of the metagreywackes of the Ranibennur area.

G-13

_ X

STD

65.22 63.07 1.48 13.53 13.90 0.61 0.40 0.45 0.06 8.00 8.98 0.94 3.06 3.92 0.49 1.46 1.50 0.24 2.91 3.65 0.48 2.05 1.95 0.33 0.08 0.09 0.03 0.14 0.10 0.03 3.14 2.34 99.99 99.99 61.30 59.30 1.99 2.43 4.60 3.90 21.30 16.50 1.80 2.20 1.50 1.90

hydraulic sorting can be evaluated through the concentration of REE in the rocks. Common accessory minerals in the metagreywackes that have a strong influence on the REE pattern include zircon, apatite, monazite and titanite (sphene). Therefore, REE patterns are examined in the light of the modal abundance of the accessory minerals. Zircon is a common detrital mineral in most terrigenous sediments (Taylor et al., 1986) and HREE contents of zircons are extremely variable (Yb = 30 to 4000 ppm; Gromet et al., 1984). Assuming that average zircon contains 55 wt.% of ZrO2, to account for 176 ppm Zr in the rocks, about 0.043 vol.% of zircon is required in modal

Fig. 5. A Chondrite normalized rare earth element plots for the metagreywackes of the Ranibennur area (Chondrite data after Sun and McDonough, 1989). Fig. 5B PAAS normalized rare earth element plots for the metagreywackes of the Ranibennur area (PAAS data after Nance and Taylor, 1977).

V.S. Hegde, V.C. Chavadi / Gondwana Research 15 (2009) 178–187 Table 4 Trace and rare earth element compositions (ppm) and elemental ratios of the metagreywackes of the Ranibennur area

Rb Sr Zr Cr V Ni Co Cu Zn Sc Hf Th U Y La Ce Pr Nd Sm Eu Gd Tb Dy Tm Yb ΣREE La/Yb Eu/Eu⁎ (Gd/Yb)N Tb/Yb Cu/Zn Th/U La/Th Zr/Y Cr/Ni Th/Sc La/Co Zr/Cr Zr/Hf Rb/Sr K/Rb La/Sc Ti/Zr Zr/Sc

X-10

X-13

X-18

62 506 132 175 129 123 25 50 47 13 3.80 6.90 2.40 15 13 34 4.3 16 3.3 0.66 3.10 0.52 2.59 0.19 1.00 80.43 13.00 0.67 2.56 0.32 1.06 2.90 1.88 8.80 1.42 0.53 0.52 0.75 34.70 0.12 287 1.00 21.82 13.2

94 546 177 221 192 145 30 61 43 16 4.30 8.40 2.70 18 18 44 5.3 21 3.9 0.90 3.10 0.51 3.01 0.20 2.20 104.8 8.18 0.89 1.17 0.23 1.42 3.10 2.14 9.80 1.52 0.52 0.50 0.91 41.20 0.17 203 1.10 14.58 11.06

84 60 733 295 191 168 209 170 143 151 132 89 26 29 83 55 43 62 15 14 4.60 4.50 6.90 7.90 2.60 2.10 20 18 18 20 45 51 5.8 6.3 21 24 4.1 5.1 0.92 1.15 3.50 4.15 0.55 0.56 3.32 3.10 0.26 0.25 2.33 2.13 107.26 120.08 7.83 9.39 0.77 0.78 1.24 1.61 0.24 0.26 1.93 0.89 2.65 3.76 2.61 2.53 9.55 9.33 1.58 1.91 0.46 0.56 0.62 0.72 0.91 0.98 4.50 37.30 0.11 0.20 148 304 1.20 1.42 11.94 15.36 12.73 12

X-26

R-7

G-6

G-7

A-26

40 228 186 154 113 115 23 60 50 14 4.20 6.80 2.40 17 37 58 9 24 6 1.23 4.50 0.50 3.00 0.20 1.50 147.53 24.66 0.79 2.48 0.33 1.20 2.83 5.44 10.94 1.34 0.48 1.61 1.20 44.30 0.17 292 2.64 9.67 13.28

57 323 179 118 94 105 21 41 54 13 3.90 7.50 2.20 18 33 59 8.9 24 6 1.28 4.50 0.50 3.36 0.20 1.80 144.84 18.33 0.82 2.07 0.28 0.76 3.40 4.40 9.94 1.12 0.58 1.57 9.51 45.90 0.17 183 2.54 17.76 13.77

66 316 215 164 89 154 22 89 48 11 3.80 7.25 1.90 18 23 42 5.3 20 4 0.76 3.50 0.72 3.10 0.22 1.75 106.35 13.14 0.66 1.65 0.41 1.85 3.81 3.17 11.94 1.06 0.66 1.00 1.31 37.00 0.20 138 2.09 12.56 19.54

58 65 263 401 161 176 196 176 140 131 103 121 21 24 54 62 42 49 12 13.5 4.10 4.15 7.20 7.35 2.30 2.32 15 17.4 28 23.7 42 42.7 6 6.4 18.4 21.0 4.4 4.6 1.17 1.00 5.40 4.00 0.40 0.50 2.10 2.90 0.20 0.21 1.60 1.80 111.07 119.29 17.50 14.00 0.87 0.78 2.70 1.95 0.40 0.31 1.28 1.26 3.13 3.17 3.89 3.20 10.73 10.10 1.90 1.45 0.60 0.55 1.33 0.98 0.82 1.00 39.30 42.40 0.22 0.16 222 222 2.33 1.79 19 14.84 13.42 13.3

Average

composition. This modal proportion, however, cannot explain the Yb contents in the rocks, even if the Yb(N) of the zircon is 4000. Presence of garnet in the source would explain high Yb content in the metagreywackes. However, HREE and Y are compatible in the garnet, and presence of such a source would result in enrichment of these elements in the metagreywackes. But, Y content in the metagreywackes is comparable to the AUCC, and high LREE/HREE patterns (La/Yb = 7.8–24.66), which preclude presence of garnet in the source. REE particularly LREE, are traces in apatite. The P2O5 content of the rocks is 0.10 wt.%. Assuming that the average apatite contains 42 wt.% P2O5, the P2O5 content in the metagreywackes corresponds to 0.04 vol.% of apatite in the modal composition. This cannot account for the La or Yb contents of the rocks. Similarly, 0.0018 vol.% of modal monazite (assuming all Th content in the Ranibennur metagreywackes is due to monazite) can account for La(N) = 16 and Yb(N) = 0.05, and 0.125 vol.% of modal sphene (assuming all TiO2 in the metagreywackes is due to titanite) can account for La(N) = 3.75 and Yb(N) = 1.25. All these four heavy minerals, if present in the above proportions, can only contribute La(N) = 20.12 and Yb(N) = 2.04. This implies that fractionation has not taken place prior to the deposition of the Ranibennur metagreywackes. During greenschist facies metamorphism, selective mobility of alkali and alkaline earth elements may be expected (c.f. Gromet et al., 1984). Wedephol (1991) has shown that the whole rock Th/U ratio is a

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sensitive indicator of metamorphism in all types of rocks; the Th/U ratios may reach 8–10 in upper amphibolite facies and as high as 25 in the granulite facies. The Th/U ratios of the Ranibennur metagreywackes remain low (average. 3.17) indicating that there was no preferential removal of U during metamorphic processes (c.f. Camire et al., 1993). Such low values also could be due to leaching of Th. As REE are relatively immobile (Rudnick et al., 1985; Elderfield and Sholkovitz, 1987), the La/Th ratio can be used to evaluate the leaching of Th if any. These metagreywacke samples have La/Th ratios comparable to AUCC (Taylor and McLennan, 1985), which suggests that only very little Th (b15%) depletion can be accommodated and hence leaching of Th is precluded. Therefore, it is inferred that chemical weathering prior to sedimentation, hydraulic sorting during transportation and sedimentation, diagenesis and low-grade metamorphism did not significantly affect the composition of the metagreywackes. Hence, the metagreywacke composition can be used to interpret the provenance. 7.2. Provenance of the Ranibennur metagreywackes Graded bedding, angular to subangular clastic grains in the metagreywackes, textural, mineralogical and chemical immaturity along with metasedimentary and igneous rock fragments all point to a magmatic arc source. It has been shown already that clastic sedimentary material of the Ranibennur metagreywackes has not been severely weathered and re-worked. Therefore, geochemical characters, in particular of REE, HFSE, Th, Hf, Zr, Y and Sc, which are relatively immobile (Taylor and McLennan, 1985), are most dependable for provenance studies. Because of their low mobility during sedimentary processes and their low residence time in seawater, these elements are almost quantitatively transferred into the sediment (Taylor and McLennan, 1985; McLennan and Taylor, 1991). Thorium is incompatible during magmatic crystallization (Taylor and McLennan, 1985) and tends to be concentrated in late-formed phases in igneous rocks, while Sc is compatible and is found disseminated in mafic minerals. Fedo et al. (1997) have shown that Th/Sc ratios are similar for both sandstone and mudstone of the Palaeo-Proterozoic Serpent Formation and argued that the sorting process did not affect the Th/Sc ratios. Th/Sc ratios have been widely used to assess the composition of the provenance. Th/Sc ratios less

Fig. 6. A–CN–K ternary diagram (mol%) showing composition of metagreywackes of the Ranibennur area. Note the Ranibennur metagreywacke has sampled Dharwar tonalitic basement gneiss.

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Fig. 7. Hf v/s La/Th source rock discrimination plot for the Ranibennur metagreywackes (after Floyd and Leveridge, 1987).

than one (0.47–0.65) for the Ranibennur metagreywackes indicate a contribution from a mafic source. However, the high ratios of SiO2/MgO (average 16.46), Zr/Cr (0.75– 1.81), Zr/Y (8.8–11.9), La/Yb (7.8–24.6) and moderate to high La/Co (average 1.03) of the Ranibennur metagreywackes reveal a dominance of felsic provenance. Ratios of Ti/Zr, Zr/Sc are useful indicators of relative contributions from basic and felsic sources. Lower Ti/Zr ratios of the Ranibennur metagreywackes (9.67 –22) compared to AUCC values (40) (Taylor and McLennan, 1985) and higher ratios of Zr/Sc of the metagreywackes (11–19.5) with regard to the AUCC (8.92) suggest relative abundance of felsic source. In the AUCC normalized multielement plot, the Ranibennur metagreywackes show enrichment of La, Ce and Th, with regard to AUCC, which corroborate felsic source such as granodiorite (Kawano et al., 2006). Floyd and Leveridge (1987) used La/Th v/s. Hf plot to discriminate between different source compositions. In the discriminatory plot, the data for the Ranibennur metagreywackes spread between the felsic and basic source for them (Fig. 7). The scatter/spread of points in discriminatory diagram are considered to be the effects of mixing of detritus from different source terrains especially in the vicinity of volcanic arcs (Basson et al., 2004). Felsic volcanic rocks have CIW values ~ 60, TTG has values of ~ 55 and granites have CIW values ~65. However, felsic volcanic components are less abundant during Archaean (Condie, 1993). The CIW values of the metagreywackes (54.4–65.4) therefore corroborate mixing from different sources. According to Taylor et al. (1986) low values of HREE, Tb/Yb (0.23–41) and high LREE (La/Yb 7.83–24.66), coupled with high Y abundances (15–20 ppm), are more likely to reflect a provenance dominated by tonalitic to trondhjemitic plutons. Rocks with the above geochemical character occur in the WDC (c.f. Rogers and Callhan, 1989; Rama Rao et al., 1991). Tonalites and trondhjemites in the source area can explain many major and trace elements such as SiO2, Al2O3, and their low TiO2. Such a source with TTG composition constitutes ~ 35–38% of the Dharwar greenstone belt (Radhakrishna and Naqvi, 1986). The values of K/Rb and Rb/Sr of the metagreywackes are consistent with the values reported for trondhjemites of the Dharwar craton (Rama Rao et al., 1991). However, they do not explain a negative Eu anomaly.

Jakes and Taylor (1974), and Taylor and McLennan (1985) have related negative Eu anomalies to the development of upper granodioritic crust accompanying fractionation of plagioclase into the lower crust. The observed negative Eu anomalies in the Ranibennur metagreywackes (Eu/Eu⁎ ~ 0.78) can be considered to indicate their derivation from an arc that had a granodioritic component. Based on the major element compositions, petrographic characteristics and heavy mineral suite (titanite and zircon dominant), a granodioritic to quartz-dioritic source composition have been proposed for these metagreywackes by Chavadi and Hegde (1988). To explain the abundance of Ni, Cr and V in metagreywackes of the WDC, a mixed source consisting of two parts of gneiss and one part of mafic rock has been proposed by Argast and Donnelly (1986). Naqvi et al. (1988) argued that 2/3 gneiss and 1/3 mafic rock proportions is inadequate to explain the observed levels of concentration of Ni, Cr and V. They consider a provenance made up of 70 vol.% tonalitic gneiss, 20 vol.% mafic–ultramafic rocks and 10 vol.% sediments. These proportions however, are inadequate to explain either the LILE concentrations in the rocks or the negative Eu anomaly, and so a granitic source component is also required. Many workers (McLennan and Taylor, 1984; Taylor and McLennan, 1985; Feng and Kerrich, 1990) have shown that the composition of Archaean clastic sedimentary rocks like greywackes can be modeled as two component mixtures of mafic–ultramafic and felsic plutonic– volcanic rocks. The Cr and Ni contents in clastic sedimentary rocks have been used to monitor the contribution from mafic and ultramafic components in the source area (McLennan and Taylor, 1984). Wronkiewicz and Condie (1987, 1989) have used the concentration of these elements for mixing calculations. In the present study, mixing calculations have been carried out using published concentrations of these elements for the Dharwar Craton in the inferred four end members, namely tonalites, granites, basalts and komatiites. Contributions from recycled sediments are assumed to be represented by their original source lithologies and therefore are not considered as a separate end member in the calculation. The relative contribution of the various sources to the Ranibennur metagreywackes is evaluated by solving the equation Y1 A + Y2 B + Y3 C + Y4 D = Y where Y1,Y2,Y3 and Y4 represent the concentrations for the given elements in the A, B, C and D end members in the source tonalite, granites, basalt and komatiite, respectively and Y is the total concentration of the element in the metagreywackes. The calculations suggest that a mixture of 50–55 vol.% tonalite, 20–25 vol.% granites, 18–20 vol.% basalt and ~ 5 vol.% komatiite could give rise to compositions matching those of the Ranibennur metagreywackes (Table 5). A straight line through the data in Fig. 5, projects onto the feldspar join at a point that indicates the plagioclase to K-feldspar ratio of the parental rock. In the case of Ranibennur metagreywackes, the provenance is dominantly tonalitic, as indicated by the projected line (Fig. 5, plagioclase: K-feldspar ratio 5.5:1). This is in agreement with the results of mixing calculations. The provenance composition Table 5 Trace element abundances (ppm) of the end members used in mixing calculations (compiled by us from the published data) Th Tonalite Granite Basalt Komatiite

8.85 13.15 0.7 -

La

Yb

Co

18 39 4.7 1.29

0.81 2.5 1.2 0.42

20 14 52 85

Summary of the mixing calculation: tonalite 50–55 vol.%, granite 20–25 vol.%, basalt 18–20 vol.%, komatiite 5 vol.% (granites and tonalities from Western Dharwar Craton from Reddy et al., 1983; Basalt from the Western Dharwar Craton, unpublished data of SDM College of Engineering and Technology,Geology laboratory; Komatiites from Subba Rao and Naqvi, 1999).

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obtained in the present work explains the observed negative Eu anomaly as well as the abundance of Ni and Cr in the rocks. On the other hand the 20 vol.% of mafic-ultramafic source envisaged by Naqvi et al. (1988) would result in a higher abundance of these elements in the metagreywackes. 8. Tectonic setting The Dharwar Craton has been central to several recent studies related to early Earth history, crust formation and supercontinent tectonics (e.g., Manikyamba and Khanna, 2007; Ray et al., 2008; Eriksson et al., in press). Bhatia and Crook (1986) suggested that the geochemical parameters, in particular immobile trace elements, could be used to discriminate the tectonic setting of the sedimentary rocks. Trace element abundance of terrigenous clastic sediments places constraints on the possible composition and tectonic setting of the early upper continental crust (Taylor et al., 1986; Feng and Kerrich, 1990). Naqvi et al. (1988), based on the geochemical characteristics of the metagreywackes from various schist belts of the Dharwar craton proposed that these metagreywackes were laid down in simatic and converging active continental margin. However, sensitive element ratios such as Zr/Hf, La/Th, and Ti/Zr of the Ranibennur metagreywackes are close to continental island arc greywackes (Table 4). Th/Sc ratios of the metagreywackes (0.47–0.65) suggest fore arc setting. In most tectonic setting where stable crust or recycled sediments are exposed, the Th/Sc ratio is less than 1 (McLennan and Taylor, 1991). In the discriminatory plots of La/Sc v/s Ti/Zr (Fig. 8) and La–Th–Sc plots (Fig. 9)(after Bhatia and Crook, 1986), most points for the Ranibennur metagreywackes lie within continental island arc. REE pattern of sedimentary rocks of Archaean greenstone belts are believed to reflect volcanic sources at active tectonic setting (Condie and Wronkiewicz, 1990). REE pattern and relative enrichments of LILE in the spider diagrams of the Ranibennur metagreywackes are similar to the patterns exhibited by the igneous rocks of subduction environments. Sedimentary basin formed in the vicinity of magmatic arc and the detritus shed from the arc rocks display such geochemical signatures (c.f. Saalmann et al., 2005). However, this tectonic setting is inconsistent with the basal Jandimatti Formation, and chemical precipitates and volcanics of the overlying Joldhal and Medur Formations that are believed to have formed in a passive margin setting and shelf and rift setting respectively (c.f.Srinivasan and Naqvi, 1990). Therefore Ranibennur

Fig. 9. La–Th–Sc plots for the discrimination of the tectonic setting of the Ranibennur metagreywackes (after Bhatia and Crook, 1986). A = oceanic island arc; B = continental island arc; C = active continental margin; D = passive margin.

metagreywackes may represent accretionary prism welded to a pericontinental sequence. Due to plate tectonic activity, metagreywackes from fore-arc basin in an active setting accreted with sequences formed on a passive margin setting, and their present day disposition is due to juxtaposition of these sequences formed in different tectonic environment. 9. Nature of Late Archaean Dharwar crust The Th/Sc ratio for the metagreywackes of the study area (~0.55) suggests a relatively minor mafic provenance and that granodiorite was the important component in the source area. The Archaean craton in South India was highly evolved at the time of Dharwar sedimentation. La/Sc of AUCC is 1.42 and that of Archaean shale has a values 1.3 ± 0.2, and for post-Archaean shale, this ratio is 2.7 ± 0.3. For the Ranibennur metagreywackes, the La/Sc ratio range from 1 to 2.64 with an average value of 1.8. La/Sc ratio for the contemporary greywackes from the Canadian Shield is 1.45 (Camire et al., 1993); 1.06 for Kalgoorlie, Australia (Taylor and McLennan, 1985); 0.54 for Fig-Tree group, South Africa (Hofmann, 2005), and 0.94 for shales from Zimbabwe (Fedo et al., 1996). These features support the inference that the Archaean crust in WDC was relatively more evolved compared to the other Cratons mentioned above. Late Archaean greywackes that are derived from a mixed provenance consisting of tonalite and mafic sources do not show negative Eu anomalies (McLennan et al., 1990). Therefore, the presence of negative Eu anomalies in the Ranibennur metagreywackes suggests that the upper granodioritic crust fractionation in the WDC had occurred more than 3 Ga ago before the deposition of Ranibennur metagreywackes. Chadwick et al. (1985) reported that granodiorites like those of Chickmagalur, constituted a part of the Western Dharwar basement. Gupta et al. (1988) report whole rock Rb–Sr isochron age of 2986 ±35 Ma for granites of Kumta and Karwar areas in the WDC. Meen et al. (1992), based on Pb isotope signatures, provided evidence for distinct middle Archaean terrain in basement Peninsular Gneiss of the WDC, which implies their derivation by intra-crustal melting. Therefore, it can be inferred that the Western Dharwar crust was highly evolved with a significant component of granodiorite, and that a stable crust was present before the accumulation of the Dharwar Supergroup. 10. Conclusions

Fig. 8. La/Sc v/s Ti/Zr plot for the discrimination of the tectonic setting of the Ranibennur metagreywackes (after Bhatia and Crook, 1986). A = oceanic island arc; B = continental island arc; C = active continental margin; D = passive margin.

From the foregoing account it can be concluded that Late Archaean metagreywackes of the Ranibennur Formation of the Dharwar

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Supergroup are of the mineralogically and chemically immature quartz- intermediate type. They were derived from a magmatic arc source area. Based on the abundance of transition group elements in the metagreywackes (Ni, Cr. Co and V) as well as Zr, and the low abundance of HREE and Y contents and Tb/Yb ratios, it is inferred that they were derived from a mixed provenance consisting of 50–55 vol.% tonalite, 20–25 vol.% granite, 18–20 vol.% basalt and ~ 5 vol.% komatiite. The sediments were deposited rapidly after a short distance of transport in a continental island arc setting. The study also indicates that the average composition of the upper crust of the Western Dharwar Craton was granodiorite, before the deposition of the Ranibennur metagreywackes. Acknowledgements The authors are sincerely thankful to the Director NGRI, Hyderabad, Andhra Pradesh (India) for the facilities extended to carry out trace elements and REE analysis, and to the Director USIC, K.U., Dharwad, for the major element analysis. Our thanks are to Prof. M. Raith, Dr. R. Srinivasan, and Dr.V.N.Vasudev for useful reviews. Dr. W.S. Fyfe; Dr. G. M. Young; Dr.C. M. Fedo; Dr. S. Swayer; Dr. G.E.Camire and Dr.Zimmarmann, read earlier version of the paper. This work was supported by research grant (F.5.5/98/S-1) funded by the University Grants Commission, New Delhi. Management of Sri Dharmasthala Manjunatheshwar College of Engineering and Technology, Dharwad extended the necessary facility and encouragement for this work. We sincerely thank them. References Argast, S., Donnelly, T.W., 1986. Compositions and sources of metasediments in the upper Dharwar Supergroup, South India. Journal of Geology 94, 215–231. Ball, P.J., Gilkes, R.J., 1987. The Mount Saddleback bauxite deposit, South Western Australia. Chemical Geology 60, 215–225. Bhatia, M.R., Crook, K.A.W., 1986. Trace element characteristics of greywackes and tectonic setting discrimination of sedimentary basins. Contributions to Mineralogy and Petrology 92, 181–193. Basson, I.J., Pewrrit, S.P., Watkeys, M.K., Menzies, A.H., 2004. Geochemical correlation between metasediments of the Mfongosi Group of the Natal sector of the Namaqua–Natal metamorphic province, South Africa and the Ahlmannryggen Group of the Grunehogna province, Antarctica. Gondwana Research 7, 57–73. Camire, G.E., Lafleche, M.R., Ludden, J.N., 1993. Archaean metasedimentary rocks from the northwestern Pontiac Sub-province of the Canadian Shield: chemical characterization, weathering and modeling of the source areas. Precambrian Research 62, 285–305. Chadwick, B., Ramakrishnan, M., Viswanatha, M.N., 1985. Bababudan-A Late Archaean intracratonic volcanosedimentary basin, Karnataka, Southern India, Part II, Structure. Journal of the Geological Society of India 26, 802–821. Chavadi, V.C., Hegde, V.S., 1988. Geology of greywackes west of Ranibennur, Dharwad district, Karnataka State. Journal of the Geological Society of India 31, 337–342. Condie, K.C., 1993. Chemical composition and evolution of the upper continental crust: contrasting results from surface samples and shales. Chemical Geology 104, 1–37. Condie, K.C., Wronkiewicz, D.J., 1990. The Cr/Th ratio in Precambrian pelites from the Kaapvaal Craton as an index of craton evolution. Earth and Planetary Science Letters 97, 256–267. Crook, K.A.W., 1974. Lithogenesis and geotectonic: the significance of compositional variations in flysch arenites (greywackes). In: Dott, R.H., Shaver, R.H. (Eds.), Modern and Ancient Geo-synclinal sedimentation. Society of Economic Geology, Palaeontology and Mineralogy, Special Publication, vol. 19, pp. 304–310. Dickinson, W.R., 1985. Interpreting provenance relations from detrital modes of sandstones. In: Zuffa, G.G. (Ed.), Provenance of Arenites. D. Reidel Publ. Co, New York, N.Y., pp. 333–361. Dickinson, W.R., Beard, L.S., Brakenridge, G.R., Erjavec, J.L., Ferguson, R.C., Inman, K.F., Knepp, R.A., Lindberg, F.A., Ryberg, P.T., 1983. Provenance of North American Phanerozoic sandstones in relation to tectonic setting. Geological Society of America Bulletin 94, 222–235. Dhana Raju, R., Varma, M.M., Padmanabhan, N., Mahadevan, T.M., 1983. I- And S-type classification of the Precambrian granitoids of Southern India and its possible relevance to mineral exploration. In: Naqvi, S.M., Rogers, J.J.W. (Eds.), Precambrians of South India, Geological Society of India Memoir, vol. 4, pp. 389–400. Eriksson, P.G., Banerjee, S., Nelson, D.R., Rigby, M.J., Catuneanu, C., Sarkar, S., Roberts, R.J., Ruban, D., Mtimkulu, M.N., Sunder Raju, P.V., in press. A Kaapval craton debate: Nucleus of an early small supercontinent or affected by an enhanced accretion event? Gondwana Research, in press. doi:10.1016/j.gr.2008.08.001. Elderfield, H., Sholkovitz, E.R., 1987. Rare earth elements in the pore waters of reducing near-shore sediments. Earth and Planetery Science Letters 82, 280–288. Fedo, C.M., Eriksson, K.A., Krogstad, E.J., 1996. Geochemistry of shales from Archaean (~ 3 Ga) Buhwa greenstone belt, Zimbabwe; implications for provenance and source area weathering. Geochimica et Cosmochimica Acta 60, 1751–1763.

Fedo, C.M., Young, G.M., Nesbitt, H.W., Hanchar, J.M., 1997. Potassic and sodic metasomatism in the Southern Province of the Canadian shield, evidence from the Palaeo-Proterozoic Serpent Formation, Huronian Supergroup, Canada. Precambrian Research 84, 17–36. Feng, R., Kerrich, R., 1990. Geochemistry of fine grained clastic sediments in the Archean Abitibi greenstone belt, Canada: implications for provenance and tectonic setting. Geochimica et Cosmochimica Acta 54, 1061–1081. Floyd, P.A., Leveridge, B.E., 1987. Tectonic environment of the Devonian Gramscatho basin, south Cornwall: framework mode and geochemical evidence from turbiditic sandstones. Geological Society of London, Journal 144, 531–542. Glikson, A.Y., 1983. Geochemistry of Archaean tholeiitic basalts and high Mg to perodotitic–komatiite suits with petrogenetic implications. In: Naqvi, S.M., Rogers, J.J.W. (Eds.), Precambrians of South India. Geological Society of India Memoir, vol. 4, pp. 183–219. Gromet, L.P., Dymek, R.F., Haskin, L.A., Korotev, R.L., 1984. The North American Shale composite. Its Composition, major and trace element characteristics. Geochimica et Cosmochimica Acta 48, 2469–2482. Gupta, J.N., Pandey, B.K., Prasad, R.N., Yadav, G.S., Rameshkumar, K., Rao, S.S., 1988. Rb–Sr Geochronology of some granitic rocks around Arabail and age of uraniferous arenite and quartz pebble conglomerate of Karnataka. Geological Society of India Memoir 9, 101–108. Harinadha Babu, P., Ponnuswamy, M., Krishnamurthy, K.V., 1981. Shimoga belt. Memoirs of Geological Survey of India, vol. 112, pp. 199–218. Hofmann, A., 2005. The geochemistry of sedimentary rocks from the Fig Tree Group, Barberton greenstone belt: implications for tectonic, hydrothermal and surface processes during mid-Archaean times. Precambrian Research 143, 23–49. Hofmann, A., Bolhar, R., Dirks, P., Jelsma, H., 2003. The geochemistry of Archaean shales derived from a mafic volcanic sequence, Belingwe greenstone belt, Zimbabwe: provenance, source area unroofing and submarine versus subaerial weathering. Geochimica et Cosmochimica Acta 67 (3), 421–440. Hughes, T.C., Hannacker, P., 1978. The determination of carbon and hydrogen in geological materials by thermal decomposition. Chemical Geology 22, 331–359. Jakes, P., Taylor, S.R., 1974. Excess Europium content in Precambrian sedimentary rocks and continental evolution. Geochimica et Cosmochimica Acta 38, 739–745. Jayaram, S., Venkatasubramanian, V.S., Radhakrishna, B.P., 1983. Geochronology and trace element distribution in some tonalite and granitic gneisses of the Dharwar craton. In: Naqvi, S.M., Rogers, J.J.W. (Eds.), Precambrians of South India. Geological Society of India Memoir, vol. 4, pp. 377–387. Johnsson, M.J., 1991. Controls on the composition of fluvial sands from a tropical weathering environments: sands of the Orinoco river drainage basin, Venezuela and Colombia. Geological Society of America Bulletin 103, 1622–1647. Kasting, J.F., 1993. Earth's early atmosphere. Science 259, 920–926. Kawano, Y., Akiyama, M., Ikawa, T., Roser, B.P., Imaoka, T., Ishioka, J., Yuhara, M., Hamamoto, T., Hayasaka, Y., Kagami, H., 2006. Whole rock geochemistry and Sr isotopic compositions of Phanerozoic sedimentary rocks in the Inner Zone of the Southwest Japan Arc. Gondwana Research 9, 126–141. Kimberley, M.M., Grandstaff, D.E., 1986. Profiles of elemental concentrations in Precambrian palaeosoles on basaltic and granitic parent materials. Precambrian Research 32, 133–154. Knauth, L.P., Lowe, D.R., 2003. High Archaean climatic temperatures inferred from oxygen isotope geochemistry of cherts in the 3.5 Ga Swaziland Supergroup, South Africa. Geological Society of America Bulletin 115, 566–580. Legault, L.M., Hattori, K., 1994. Late Archaean geological development recorded in the Timiskaming group sedimentary rocks, Kirkland Lake area, Abitibi greenstone belt, Canada. Precambrian Research 68, 23–42. Maniar, P.D., Piccoli, P.M., 1989. Tectonic discrimination of granitoids. Geological Society of America Bulletin 101, 635–643. Manikyamba, C., Khanna, T.C., 2007. Crustal growth process as illustrated by the Neoarchean intraoceanic magmatism from Gadwal greenstone belt, Eastern Dharwar Craton, India. Gondwana Research 11, 476–491. McLennan, S.M., 1984. Petrological characteristics of Archaean greywackes. Journal of Sedimentary Petrology 54, 889–898. McLennan, S.M., Taylor, S.R., 1984. Archaean sedimentary rocks and their relation to the composition of the Archean continental crust. In: Kroner, A., Hanson, G.N., Goodwin, A.M. (Eds.), Archean Geochemistry. Springer-Verlag. McLennan, S.M., Taylor, S.R., 1991. Sedimentary rocks and crustal evolution: tectonic setting and secular trends. Journal of Geology 99, 1–21. McLennan, S.M., Taylor, S.R., McCulloch, M.T., Maynard, J.B., 1990. Geochemical and Nd– Sr isptopic composition of deep-sea turbidites: crustal evolution and plat tectonic associations. Geochimica et Cosmochimica Acta 56, 2015–2050. McLennan, S.M., Hemming, S., McDaniel, D.K., Hansson, G.N., 1993. Geochemical approaches to sedimentation, provenance, and tectonics. Geological Society of America, Special Paper 284, 21–40. Meen, J.K., Rogers, J.J.W., Fullahgar, P.D., 1992. Lead isotope composition of the Western Dharwar Craton, Southern India; evidence for distinct Middle Archaean terrain in a Late Archaean craton. Geochimica et Cosmochimica Acta 56, 2455–2470. Naqvi, S.M., Sawkar, R.H., Subba Rao, D.V., Govil, P.K., Rao, T.G., 1988. Geology, geochemistry and tectonic setting of Archaean greywacke from Karnataka nucleus, India. Precambrian Research 39, 193–216. Nance, W.B., Taylor, S.R., 1977. Rare earth element patterns and crustal evolution-II; Archaean sedimentary rocks from Kalgoorlie, Australia. Geochimica et Cosmochimica Acta 41, 225–251. Nesbitt, H.W., Young, G.M., 1996. Petrogenesis of sediments in the absence of chemical weathering; effects of abrasion and sorting on bulk composition and mineralogy. Sedimentology 43, 341–358.

V.S. Hegde, V.C. Chavadi / Gondwana Research 15 (2009) 178–187 Nesbitt, H.W., McLennan, S.M., Keays, R.R., 1996. Effects of chemical weathering and sorting on the petrogenesis of siliciclastic sediments, with implications for provenance studies. Journal of Geology 104, 525–542. Nesbitt, H.W., Fedo, C.M., Young, G.M., 1997. Quartz and feldspar stability, steady and non steady state weathering and petrogenesis of siliciclastic sands and muds. The Journal of Geology 109, 173–191. Plank, T., Langmuir, C.H., 1988. An evaluation of the global variations in the major element chemistry of arc basalts. Earth and Planetary Science Letters 90, 349–370. Radhakrishna, B.P., Naqvi, S.M., 1986. Precambrian continental crusts of India and its evolution. The Journal of Geology 94, 145–166. Rama Rao, P., Naqvi, S.M., Govil, P.K., Balaram, V., 1991. Geochemistry of trondhjemites from Sigegudda, Hassan District, Karnataka. Journal of the Geological Society of India 37, 351–358. Ray, R., Shukla, A.D., Sheth, H.C., Ray, J.S., Duraiswami, R.A., Vanderkluysen, L., Rautela, C. S., Mallik, J., 2008. Highly heterogeneous Precambrian basement under the central Deccan Traps, India: direct evidence from xenoliths in dykes. Gondwana Research 13, 375–385. Reddy, G.R., Pant, D.R., Sankar Das, M.,1983. Trace element geochemistry of granitic rocks of the Dharwar Craton, Karnataka State, India. In: Naqvi, S.M., Rogers, J.J.W. (Eds.), Precambrians of South India. Geological Society of India Memoir, vol. 4, pp. 329–342. Rogers, J.J.W., Callhan, E.J., 1989. Diapiric trondhjemites of the Western Dharwar Craton, Southern India. Canadian Journal of Earth Science 26, 244–256. Rudnick, R.L., McLennan, S.M., Taylor, S.R., 1985. Large ion lithophile elements in the rocks from high-pressure granulite facies terrain. Geochimica et Cosmochimica Acta 49, 1645–1655. Saalmann, K., Remus, M.V.D., Hartmann, L.A., 2005. Geochemistry and crustal evolution of volcanosedimentary successions and Orthogneisses in the São Gabriel block, Southernmost Brazil-Relics of Neoproterozoic Magmatic Arcs. Gondwana Research 8, 143–161. Sawyer, E.W., 1986. The influence of source rock type, chemical weathering and sorting on the geochemistry of clastic sediments from the Quebec metasedimentary belt, Superior Province, Canada. Chemical Geology 55, 77–93. Srinivasan, R., Naqvi, S.M., 1990. Some distinctive trends in the evolution of the Early Precambrian (Archaean) Dharwar craton, South India. Precambrian Continental Crust and its economic resources-Developments in Precambrian Geology. Elsevier, pp. 245–266.

187

Srinivasan, R., Subba Rao, D.V., Pantulu, G.V.C., Sivaraman, T.V., Balaram, V., Gopalan, K., 1992. Negative Europium anomalies and reset RbSr ages of Archaean detrital metasedimentary rocks of the low grade supracrustal belts of the Dharwar craton, South India. In: Glover, J.E., Ho, S.E. (Eds.), The Archaean; Terrains Processes and Metallogeny, vol. 22. Geology Department Key Centre and University Extension, The University of Western Australia, pp. 295–304. Subba Rao, D.V., Naqvi, S.M., 1999. Archaean komatiites from the older schist belt of Kalyadi in Western Dharwar Craton, Karnataka. Journal of the Geological Society of India, 53, 347–354. Sun, S.S., McDonough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: Saunders, A.D., Norry, M. (Eds.), Magmatism in the ocean basins. Geological Society London Special Publication, vol. 42, pp. 313–345. Swami Nath, J., Ramakrishnan, M., 1981. Early Precambrian Supra-crustals of Southern Karnataka (A) present classification and correlation. Geological Survey of India Memoir, vol. 112, pp. 261–276. Taylor, S.R., McLennan, S.M., 1985. The continental Crust: Its composition and evolution. Blackwell, Oxford, p. 312. Taylor, S.R., Rudnick, R.L., McLennan, S.M., Eriksson, K.A., 1986. Rare earth element patterns in Archaean high-grade metasediments and their tectonic significance. Geochimica et Cosmochimica Acta 50, 2267–2279. Thomson, M., Walsh, J.N., 1989. Handbook of Inductively coupled plasma spectrometry. II Edn. Balckie Glasgow and London. Published in U.S.A. by Chaman and Hall, New York. Wilson, A.H., Versfeld, A.V., 1994. The early Archaean Nondwini greenstone belt, Southern Kaapvaal Craton, Soutrh Africa, part II, characteristics of the volcanic rocks and constraints on magma genesis. Precambrian Research 67, 277–320. Wronkiewicz, D.J., Condie, K.C., 1987. Geochemistry of Archaean shales from the Witwatersrand Supergroup, South Africa: source-area weathering and provenance. Geochimica et Cosmochimica Acta 51, 2401–2416. Wronkiewicz, D.J., Condie, K.C., 1989. Geochemistry and provenance of sediments from the Pongola Supergroup, South Africa: evidence for a 3.0 Ga-old continental craton. Geochimica et Cosmochimica Acta 53, 1537–1549. Wedephol, K.H., 1991. Chemical composition and fractionation of the continental crust. Geologische Rundschau 80, 207–223.