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Study On The Characteristics And Metallogenic Conditions Of Copper-Polymetallic Deposits In Middle-northern Lanping Basin, Western Yunnan

Posted on:2007-02-18Degree:DoctorType:Dissertation
Country:ChinaCandidate:H B ZhaoFull Text:PDF
GTID:1100360185497391Subject:Mineralogy, petrology, ore deposits
Abstract/Summary:PDF Full Text Request
Sanjiang area is located at the junction between two giant orogenic belts, the Tethyan and the Circum-Pacific, and affected by the convergence of Eurasian, Indian and Pacific three plates. It has a complicate history from the formation and evolution of the Tethys to India-Eurasia collision and uplift of the plateau. The complicate tectonic settings result in abundant mineral resources. The Sanjiang metallogenic belt thus becomes one of the most important bases of mineral resources for precious and base metals in China, and also an integrate part of the world-scale Tethyan metallogenic belt.Lanping basin is located in the middle part of the Sanjiang orogenic belt between the Jinshajiang fault and the Lancangjiang fault zones. It underwent a two-stage evolution, that is, the stage of back-arc basin / foreland basin from middle Triassic to early Cretaceous, and the stage of slip pull-part basin in the Cenozoic. Huge accumulation of metals such as lead, zinc, copper and silver took place during this process and formed a well-known metal-concentrated region, including the formation of the Jinding world-class super-giant Pb-Zn deposit.Mineralization took place mainly in tectonic settings of India- Eurasia collision in the period from Eocene to early Miocene (about 56-21 Ma). The main type of ore deposits are hydrothermal sedimentary rework type. Himalayan Jinshajiang fault and Lanchangjiang fault on both side of the basin and the"central-axial fault"in the middle of the basin played a role as passageway for ore fluids. These faults are the channels for the deep-seated thermal brine to move up. The upper Triassic Sanhedong formation (T3s) consists of carbonate of shallow marine facies. The middle Jurassic Hakaizuo formation (J2h), lower Cretaceous Jingxing formation (K1j) and Nanxin formation (K1n) are composed of terrestrial red beds of clastic rocks. These formations are main host rocks for ores. The carbonate layer is rich in 17 elements such as Cu, Pb, Zn, As, Sb and so on, especially rich in Co, Ba and Sc. The sandstone is rich in 13 elements, such as Cu, Pb, Zn, V and P, especially in Co, Ni, Sb, Sc, Mn, Ba and Th. Studies in geochemistry, stable and radiogenic isotopes of ores, gangues and fluid inclusions suggest that mineralization in Lanping basin is characterized by multiple sources for metals, from either the strata in the basins or deep in the Earth's interior. Ore-forming fluids consist of brine in the basin, meteoric water and magmatic fluid.Study on limited outcrops of igneous rocks in the basin suggests that mineralization may somewhat be related to magmatism, although only few igneous rocks crop out within the basin. The ages of mineralization are nearly coeval to those of emplacement of igneous rocks. A minette dike was found near Jingding deposit in this work, confirming inferred hidden intrusions...
Keywords/Search Tags:Yunnan, Lanping basin, Cu - pollymetamic deposits, fluid inclusion, zonation of ore deposits
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