Carbon isotope studies of auriferous quartz carbonate veins from two orogenic gold deposits from the Neoarchean Chitradurga schist belt, Dharwar craton, India: Evidence for mantle/magmatic source of auriferous fluid

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• 作者：S. Sarangi^a ; ^{ssarangi2@rediffmail.com} ; A. Sarkar^b ; R. Srinivasan^c ; S.C. Patel^d
• 关键词：Carbon isotopes ; Oxygen isotopes ; Archaean ; Orogenic gold deposits ; Dharwar craton ; Southern India
• 刊名：Journal of Asian Earth Sciences
• 出版年：2012
• 期刊代码：40_13679120
• 类别：ear
• 出版时间：30 June, 2012
• 卷：52
• 期：Complete
• 页码：1-11
• 文件大小：2113 K

摘要

Carbon and oxygen isotopic compositions of carbonates from auriferous quartz carbonate veins (QCVs) of two orogenic gold deposits - Ajjanahalli and Guddadarangavvana Halli (G.R. Halli) - from the Neoarchean Chitradurga schist belt of the Dharwar craton, southern India are examined to understand the origin of the mineralizing fluids. The average carbonate carbon (未¹³C_pdb) and oxygen (未¹⁸O_smow) isotope compositions of QCVs of Ajjanahalli are 鈭?.5 卤 1.3鈥?and 14.1 卤 2.7鈥? respectively. The same ratios for the QCVs of G.R. Halli are 鈭?.2 卤 1.9鈥?and 14.1 卤 0.5鈥? The corresponding average fluid 未¹³C and 未¹⁸O compositions are 鈭?.81 卤 1.14鈥? 13.78 卤 5.1鈥?for Ajjanahalli and 鈭?.64 卤 0.7鈥? 鈭?.50 卤 0.6鈥?for G.R. Halli. The 未¹³C_pdb of syn-sedimentary carbonates of BIF of Ajjanahalli (鈭?.8 卤 0.1鈥?, carbonated metabasalts of Ajjanahalli (鈭?.4鈥? and G.R. Halli (鈭?.3鈥? fall in the compositional range of marine carbonates (0 卤 2鈥?. As dissolution/decarbonation reactions during metamorphism of pre-existing carbonate/carbonated rocks produce CO₂ with 未¹³C values similar to or more enriched than parent rock, the carbonate or fluid 未¹³C ratios of the QCVs (which fall in the compositional range of mantle/magmatic derived CO₂ or carbonates) obtained in this work cannot be the result of metamorphism. It is proposed that gold mineralizing fluids were derived from juvenile magmatic melts and were channeled through crustal scale shear zones to give rise to the gold deposits.