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A study of granite typology in Sanandaj-Sirjan zone, Zagros Orogen, Iran
A570
Goldschmidt Conference Abstracts 2006
A study of granite typology in SanandajSirjan zone, Zagros Orogen, Iran
Ni isotope fractionation during lateritization of serpentinites
ALI A. SEPAHI1, SEYED F. ATHARI2
S.A. SERGEEV, L.E. MORDBERG, R.S. KRYMSKY, I.N. KAPITONOV, V.P. KLINDUKHOV
1
Department of Geology, Bu Ali Sina University, Hamadan, Iran Department of Geology, Bu Ali Sina University, Hamadan and Young Researchers Club of Kurdistan, Iran
2
Centre of Isotopic Research, VSEGEI, St. Petersburg, Russia ([email protected])
Each granitoid type is generated and emplaced in every specific tectonic setting and each stage of the Wilson cycle is characterized by typical associations of granitoids. Field, mineralogical, petrological and geochemical characteristics are important for subdivision of granites to several types (Barbarin, 1990; Barbarin, 1999). Various types of granitic rocks occur in Sanandaj-Sirjan zone, Zagros Orogen, Iran. Outcrops of S-type granites have been reported from many localities such as Hamadan (Alvand), Azna, Kolahghazi and Muteh. I-type, M-type and H-type granites have been studied in many parts of Sanandaj-Sirjan zone such as Hamadan (Alvand), Boroujerd, Astaneh, Saqqez and Ghorveh. A-type granites are less abundant but have been reported from some localities such as Saqqez and Almagholagh. Radiometric ages have indicated upper Jurassic to Tertiary ages for major plutonic bodies, specially for granitic rocks of Sanandaj-Sirjan zone. These bodies indicate a magmatic suite of an arc setting followed by collisional and post-collisional magmatism. With considering plagiogranites of Kermanshah ophiolitic complex, a nearly complete range of plutonism related to a Wilson cycle can be observed in Sanandaj-Sirjan zone during Mesozoic Era.
No fractionation of Ni isotopes which sufficiently exceeded analytical errors is mentioned in recent compilations. However, a presupposition existed that Ni isotope fractionation could be observed in such low-temperature formations as laterites rather than in magmatic or other high-temperature rocks. Our study was aimed at searching possible variations in Ni isotope composition in a system ‘‘ultrabasic rock—laterite’’. Subject for study were Proterozoic serpentinite from the Wind Belt (Baltic Shield) and Lower Carboniferous lateritic profile formed at the expense of it. The profile is well-zoned and reaches 40 m thick. The main Ni-bearing minerals are montmorillonite and goethite; bulk Ni content usually does not exceed 1 wt%. Another set of samples was Early Paleozoic serpentinite from the Ufaley Region, Central Urals, and its alteration products from the Ufaley Ni deposit aged Lower Cretaceous. The deposit belongs to the contact-karst type; laterite is partly preserved on serpentinites and partly redeposited in karstic caves along the contact of serpentinites with the nearest marbles. The content of Ni varies from 0.6–0.7 wt% in leached serpentinites to 9 wt% in garnierite stockwork. The other lateritic profile (Serov deposit) occurs in the Northern Urals. It was formed in Late Triassic over Paleozoic serpentinized harzburgites and covered by Early Jurassic sediments. Weathered products are characterized by low Ni content (usually 1 wt% and less). All of samples had undergone preliminary total acid dissolution; Ni separation was made consequently on chromatographic columns using Bio-Rad AG MP-1 and Eichrom Ni resins. Ni isotope analyses were carried out on the MC-ICP-MS Neptune (Thermo Finnigan). Correction for instrument mass bias was made using exponential mass fractionation law (65Cu/63Cu = 0.44625). For this, in-house Cu standard was added to the sample solution before measurements. The method of bracketing was used for the analyses performance as well. This provided double control over the results obtained. The long-term reproducibility of our analytical work was ±0.03& for d60Ni and ±0.01& for d62Ni. With respect to Ni isotope composition of parent serpentinites, samples of garnierite ore of infiltration genesis show more heavy composition, while oxidised laterite samples have more easy composition. Dependance of isotope effect on the intensity of weathering is observed. Thus, the smallest Ni isotope fractionation is observed for the samples from the Serov deposit which formed during least productive Triassic epoch. Maximum isotope effect is found for samples from the Ufaley deposit formed during most productive Cretaceous weathering epoch.
References Barbarin, B., 1990. Granitoids—main petrogenetic classifications in relation to origin and tectonic setting. Geological Journal 25 (3-4), 227–238. Barbarin, B., 1999. A review of the relationships between granitoid types, their origins and their geodynamic environments. Lithos 46 (3), 605–626. doi:10.1016/j.gca.2006.06.1055
doi:10.1016/j.gca.2006.06.1056
Goldschmidt Conference Abstracts 2006
A study of granite typology in SanandajSirjan zone, Zagros Orogen, Iran
Ni isotope fractionation during lateritization of serpentinites
ALI A. SEPAHI1, SEYED F. ATHARI2
S.A. SERGEEV, L.E. MORDBERG, R.S. KRYMSKY, I.N. KAPITONOV, V.P. KLINDUKHOV
1
Department of Geology, Bu Ali Sina University, Hamadan, Iran Department of Geology, Bu Ali Sina University, Hamadan and Young Researchers Club of Kurdistan, Iran
2
Centre of Isotopic Research, VSEGEI, St. Petersburg, Russia ([email protected])
Each granitoid type is generated and emplaced in every specific tectonic setting and each stage of the Wilson cycle is characterized by typical associations of granitoids. Field, mineralogical, petrological and geochemical characteristics are important for subdivision of granites to several types (Barbarin, 1990; Barbarin, 1999). Various types of granitic rocks occur in Sanandaj-Sirjan zone, Zagros Orogen, Iran. Outcrops of S-type granites have been reported from many localities such as Hamadan (Alvand), Azna, Kolahghazi and Muteh. I-type, M-type and H-type granites have been studied in many parts of Sanandaj-Sirjan zone such as Hamadan (Alvand), Boroujerd, Astaneh, Saqqez and Ghorveh. A-type granites are less abundant but have been reported from some localities such as Saqqez and Almagholagh. Radiometric ages have indicated upper Jurassic to Tertiary ages for major plutonic bodies, specially for granitic rocks of Sanandaj-Sirjan zone. These bodies indicate a magmatic suite of an arc setting followed by collisional and post-collisional magmatism. With considering plagiogranites of Kermanshah ophiolitic complex, a nearly complete range of plutonism related to a Wilson cycle can be observed in Sanandaj-Sirjan zone during Mesozoic Era.
No fractionation of Ni isotopes which sufficiently exceeded analytical errors is mentioned in recent compilations. However, a presupposition existed that Ni isotope fractionation could be observed in such low-temperature formations as laterites rather than in magmatic or other high-temperature rocks. Our study was aimed at searching possible variations in Ni isotope composition in a system ‘‘ultrabasic rock—laterite’’. Subject for study were Proterozoic serpentinite from the Wind Belt (Baltic Shield) and Lower Carboniferous lateritic profile formed at the expense of it. The profile is well-zoned and reaches 40 m thick. The main Ni-bearing minerals are montmorillonite and goethite; bulk Ni content usually does not exceed 1 wt%. Another set of samples was Early Paleozoic serpentinite from the Ufaley Region, Central Urals, and its alteration products from the Ufaley Ni deposit aged Lower Cretaceous. The deposit belongs to the contact-karst type; laterite is partly preserved on serpentinites and partly redeposited in karstic caves along the contact of serpentinites with the nearest marbles. The content of Ni varies from 0.6–0.7 wt% in leached serpentinites to 9 wt% in garnierite stockwork. The other lateritic profile (Serov deposit) occurs in the Northern Urals. It was formed in Late Triassic over Paleozoic serpentinized harzburgites and covered by Early Jurassic sediments. Weathered products are characterized by low Ni content (usually 1 wt% and less). All of samples had undergone preliminary total acid dissolution; Ni separation was made consequently on chromatographic columns using Bio-Rad AG MP-1 and Eichrom Ni resins. Ni isotope analyses were carried out on the MC-ICP-MS Neptune (Thermo Finnigan). Correction for instrument mass bias was made using exponential mass fractionation law (65Cu/63Cu = 0.44625). For this, in-house Cu standard was added to the sample solution before measurements. The method of bracketing was used for the analyses performance as well. This provided double control over the results obtained. The long-term reproducibility of our analytical work was ±0.03& for d60Ni and ±0.01& for d62Ni. With respect to Ni isotope composition of parent serpentinites, samples of garnierite ore of infiltration genesis show more heavy composition, while oxidised laterite samples have more easy composition. Dependance of isotope effect on the intensity of weathering is observed. Thus, the smallest Ni isotope fractionation is observed for the samples from the Serov deposit which formed during least productive Triassic epoch. Maximum isotope effect is found for samples from the Ufaley deposit formed during most productive Cretaceous weathering epoch.
References Barbarin, B., 1990. Granitoids—main petrogenetic classifications in relation to origin and tectonic setting. Geological Journal 25 (3-4), 227–238. Barbarin, B., 1999. A review of the relationships between granitoid types, their origins and their geodynamic environments. Lithos 46 (3), 605–626. doi:10.1016/j.gca.2006.06.1055
doi:10.1016/j.gca.2006.06.1056