The Baimazhai Ni-Cu-PGE (platinum-group-elements) sulfide deposit, southeast Yunnan Province, is hosted in mafic-ultramafic intrusions of the Permian Emeishan large igneous province, with which it is temporally and genetically related. The typical orthomagmatic sulfide ores of the Baimazhai deposit locally exhibit peculiar textural features, and are intimately associated with hydrothermal minerals such as biotite, amphibole, and chlorite. This suggests that magmatic sulfide ores were subjected to hydrothermal alteration and subsequent redistribution, resulting in enrichment in Cu, Pd, and Au. Whole-rock 40 Ar-39 Ar age data yielded plateau ages of about 160-170 Ma, at odds with the established Permian age of the host intrusions and the Emeishan large igneous province. We interpret these younger ages as due to thermal resetting during post-Permian tectonothermal events such as the Jurassic Cretaceous Yanshanian orogeny, and propose a model in which tectonic movements and hydrothermal fluids modified the pre-existing magmatic sulfides. Given the high degree of overprinting, we suggest two possible scenarios: (1) sulfide disseminations that surround the massive magmatic ores are the result of deformation and hydrothermal alteration; and (2) both magmatic massive and disseminated sulfides were produced initially, in which case the scale and metasomatic remobilization would have been smaller, but still detectable.
The Kangdian axis basement can be divided into two tectonic layers. The lower tectonic layer is the crystalline basement which is made up of the Archaean Dibadu Formation and early Proterozoic Dahongshan Group. The former is a kata‐metamorphic basic volcano‐sedimentary formation of the old geosyncline (old continental nucleus), and the latter is a medium‐grade metamorphosed alkali‐rich basic volcanic (emanation)‐sedimentary formation of the Yuanjiang‐Dahongshan marginal rift. They are in disconformable contact. The upper tectonic layer is the folded basement, and made up of the middle‐late Proterozoic Kunyang Group. It is the result of Dongchuan‐Yuanjiang intercontinental rifting with discordant contract with the underlying and overlying strata. Along with the evolution of Proterozoic from early to late, four types of emanation‐sedimentary deposits in the Kangdian axis rift were formed in turn: emanation‐sedimentary iron‐copper‐gold deposits related to basic volcanic rocks in the Yuanmou‐Dahongshan marginal rift; emanation‐sedimentary iron‐copper deposits related to intermediate‐basic volcanic rocks in the early stage of the Dongnchuan‐Yuanjiang intercontinental rift; emanation‐sedimentary copper deposits related to sedimentary rocks in the middle stage; copper deposits related to the late tectonic reworking. From early to late Proterozoic, with the evolution of the Kangdian axis rift and lowering volcanic basicity, the ore‐forming elements also evolved from Fe, Cu and (Au) through Cu and Fe to Cu.
To compile the software package of the mine digitization information system in terms of the principle and methods of mathematics geology and geographic information system using computer languages such as VB and Matlab, this paper introduces the function composition and operating environment of this information system, and illustrates the function and effectiveness of the software package as exemplified by the Lanping Pb-Zn mine, Yunnan Province.
The sulphide ores of the Baimazhai deposit, although typically orthomagmatic, locally exhibit peculiar textural features and are intimately associated with hydrothermal minerals, such as biotite, amphibole and chlorite. This association suggests that the magmatic sulphide ores were subjected to hydrothermal alteration and subsequent redistribution, resulting in the observed textural features. Geochemically, the Baimazhai sulphide ores are enriched in Cu, Pd and Au, which according to previous studies, reflects the action of hydrothermal fluids. Interestingly, Ar-Ar dating yielded the plateau ages of about 160-170 Ma, which are at odds with the established Permian age of the Emeishan large igneous province. We interpreted these younger ages as due to thermal resetting during post-Permian tectonothermal events. We have proposed a model in which tectonic movements and hydrothermal fluids related to these events modified the pre-existing magmatic sulphides. Given the degree of overprint, we suggested two possible scenarios: 1) the sulphide disseminations that surround the massive magmatic ores are the result of deformation and hydrothermal alteration; and 2) there were both magmatic massive and disseminated sulphides, in which case the scale and relocation of remobilization would have been smaller, but still detectable.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.