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Tectonic significance of dykes in the Sarnu-Dandali alkaline complex,Rajasthan, northwestern Deccan Traps 被引量:1
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作者 Anjali Vijayan Hetu Sheth Kamal Kant Sharma 《Geoscience Frontiers》 SCIE CAS CSCD 2016年第5期783-791,共9页
Whether swarms of preferentially oriented dykes are controlled by regional stress fields, or passively exploit basement structural fabric, is a much debated question, with support for either scenario in individual cas... Whether swarms of preferentially oriented dykes are controlled by regional stress fields, or passively exploit basement structural fabric, is a much debated question, with support for either scenario in individual case studies. The Sarnu-Dandali alkaline complex, near the northwestern limit of the Deccan Traps continental flood basalt province, contains mafic to felsic alkaline volcano-plutonic rocks and carbonatites. The complex is situated near the northern end of the 600 km long, NNWe SSE-trending Barmer-Cambay rift. Mafic enclave swarms in the syenites suggest synplutonic mafic dykes injected into a largely liquid felsic magma chamber. Later coherent dykes in the complex, of all compositions and sizes,dominantly strike NNWe SSE, parallel to the Barmer-Cambay rift. The rift formed during two distinct episodes of extension, NWe SE in the early Cretaceous and NEe SW in the late Cretaceous. Control of the southern Indian Dharwar structural fabric on the rift trend, as speculated previously, is untenable,whereas the regional Precambrian basement trends(Aravalli and Malani) run NEe SW and NNEe SSW.We therefore suggest that the small-scale Sarnu-Dandali dykes and the much larger-scale BarmerCambay rift were not controlled by basement structure, but related to contemporaneous, late Cretaceous regional ENEe WSW extension, for which there is varied independent evidence. 展开更多
关键词 Dyke swarms alkaline magmatism Deccan Traps Sarnu-Dandali Barmer-Cambay rift
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Regional Metallogenesis of the Chang'an Gold Ore Deposit in Western Yunnan:Evidences from Fluid Inclusions and Stable Isotopes 被引量:10
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作者 CHEN Yue LIU Junlai +2 位作者 TRAN My Dung LI Yongchao BING Mingming 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2010年第6期1401-1414,共14页
The Chang'an gold ore deposit in western Yunnan is located at the southern segment of the Ailaoshan metallogenic belt.The ore bodies are preserved in fractured Ordovician sedimentary clastic rocks.The gold-bearing mi... The Chang'an gold ore deposit in western Yunnan is located at the southern segment of the Ailaoshan metallogenic belt.The ore bodies are preserved in fractured Ordovician sedimentary clastic rocks.The gold-bearing minerals occur dominantly in sulfide-quartz veins.Fluid inclusion analysis shows that the Chang'an gold ore deposit is characterized by epithermal gold mineralization at temperatures between 200℃and 280℃at a shallow crustal level.The mineralizing fluids have intermediate to low salinity(6%-18%) and low densities(0.72-1.27 g/cm^3).The ore minerals haveδ^(34)S in a range from -13‰to 3.57‰,concentrated from -2.06‰to 3.57‰with an average of 1.55‰.The ^(206)Pb/^(204)Pb,^(207)Pb/^(204)Pb and ^(208)Pb/^(204)Pb values are 18.9977-19.5748,15.7093-15.784,39.3814-40.2004 respectively.These isotope data suggest that the ore-forming elements were mainly derived from mixed crustal and mantle sources.The Chang'an gold ore deposit and Tongchang Cu-Mo deposit are closely related to each other in their spatial distribution and age of formation.They have similar sources of mineralizing elements and identical ore-forming metal elements,and show a close relationship in physical and chemical conditions of mineralization.The two deposits constitute an epithermal-porphyry -skarn type Cu-Mo-Au mineralization system in the Tongchang-Chang'an area,which is related to the Cenozoic high-K alkaline magmatism. 展开更多
关键词 Indian-Eurasian continental collision Ailaoshan metallogenic belt high potassic alkaline magmatism epithermal gold deposit Western Yunnan
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