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Jia R.-X.,Chinese Academy of science | Jia R.-X.,Beijing Exploration Technology Center for Mineral Resources | Jia R.-X.,Beijing Donia Resources Co. | Fang W.-X.,Chinese Academy of science | And 2 more authors.
Kuangwu Yanshi/ Journal of Mineralogy and Petrology | Year: 2011

The NM deposit is located in the northwest trending magmatic-tectonic belt, northcentral part of Truong Son, which was subjected to right-lateral shearing due to the collision of Sibumasu micro-continent with Indo-China micro-continent along Nan-Uttaradit suture during Permian-Triassic Period. Based on the grain size and spatial distribution,the granites in NM deposit can be classified into medium-coarse grained granite, porphyritic granite and fine grained granite respectively. The geochemical characteristics of different types of granite show that they are high-potassium, calc-alkaline granitoids with the ACNK ratios mostly ranging from 0.9 to 1. 1. Trace elements of the granites show that the variety of LILE enriches in Cs, Rb, Th, U,K, while depletes in Ba and Sr,distinct fractionation of HFSE with clearly negative anomaly of Nb,P and Ti. REE analysis reveals relative high content and distinct fractionation of LREE in contrast to HREE,and moderate to sharp negative Eu anomaly. All of the geochemical features indicate that these different types of granites in NM deposit were derived from the same origin related to the special tectonic setting of post-collision volcanic arc. During the magmatic evolution process from early stage represented by medium-coarse grained granite to last stage represented by fine grained granite, the TFe, TiO 2, MgO 1CaO and Na 2O contents in magma tend to decrease, while the SiO 2 and K 2O contents increase gradually, and the Fe,Cu and Zn (Pb) mineralization is mainly related to the porphyritic granite.

Jia R.,Chinese Academy of science | Jia R.,Beijing Exploration Technology Center for Mineral Resources | Jia R.,Beijing Donia Resources Co. | Fang W.,Chinese Academy of science | And 2 more authors.
Journal of Rare Earths | Year: 2010

The NM copper polymetal deposit is located in the middle north part of the Truong Son metallogenic belt in Laos, which is the skarn-typed deposit and located in the contact between Indosinian granite and Lower Carboniferous limestone. All the ore-bodies in NM deposit can be divided into four types according to their occurrences: I copper ore-body as the massive restite developed in inner contact near the granite in north part; II-1 zinc-copper ore body and II-2 copper-iron ore body developed within contact between the granite and carbonate rocks, III copper-zinc ore body developed in the cranny among the southern carbonate stratum, indicating that all the ore-bodies were related to Indosinian granite emplacing into the Carboniferous limestone and causing the metallogenic system from closed state getting into half open state. The geochemical characteristics and mineral assemblages of them showed that all the orebodies in NM deposit derived from a similar origin and their ore-forming fluids with the evolution trend from reductive state in early stage to oxidative state in later stage were mainly related to the coupling interaction between post-magmatic hydrothermal fluid and basin fluid. Copyright © 2012 Elsevier B.V.

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