The Baimazhai Ni-Cu- (PGE) sulphide deposit in southeast Yunnan Province is hosted in mafic-ultramafic intrusions associated with the Permian Emeishan large igneous province. The deposit, one of several in the provinc...The Baimazhai Ni-Cu- (PGE) sulphide deposit in southeast Yunnan Province is hosted in mafic-ultramafic intrusions associated with the Permian Emeishan large igneous province. The deposit, one of several in the province, exhibits field and petrographic features suggestive of post-magmatic modification. The mafic-ultramafic intrusions that host the Baimazhai sulphide ores show near-pervasive to pervasive hydrothermal alteration, with the sulphides be- ing spatially associated with hydrothermal minerals such as biotite, amphibole and chlorite. This intimate association suggests that the sulphide ores were subjected to deformational and hydrothermal redistribution and textural changes resulting in disseminated and brecciated ores. Geochemically the Baimazhai sulphide ores are enriched in Cu, Pd and Au which, according to published studies, reflects the action of hydrothermal fluids. Interestingly, Ar-Ar age data yielded plateau ages of about 160-170 Ma, which also supports the modification features of the sulfide ores.展开更多
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 chlorit...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.展开更多
基金Projects 2002GH11 supported by the International Coorperation Project of Yunnan Province and 2003D0039Q by The Natural Science Fund of Yunnan Province
文摘The Baimazhai Ni-Cu- (PGE) sulphide deposit in southeast Yunnan Province is hosted in mafic-ultramafic intrusions associated with the Permian Emeishan large igneous province. The deposit, one of several in the province, exhibits field and petrographic features suggestive of post-magmatic modification. The mafic-ultramafic intrusions that host the Baimazhai sulphide ores show near-pervasive to pervasive hydrothermal alteration, with the sulphides be- ing spatially associated with hydrothermal minerals such as biotite, amphibole and chlorite. This intimate association suggests that the sulphide ores were subjected to deformational and hydrothermal redistribution and textural changes resulting in disseminated and brecciated ores. Geochemically the Baimazhai sulphide ores are enriched in Cu, Pd and Au which, according to published studies, reflects the action of hydrothermal fluids. Interestingly, Ar-Ar age data yielded plateau ages of about 160-170 Ma, which also supports the modification features of the sulfide ores.
文摘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.
