Sources of fluids and metals and evolution models of skarn deposits in the Qimantagh metallogenic belt: A case study from the Weibao deposit, East Kunlun Mountains, northern Tibetan Plateau.
Zhong, S; Feng, C; Seltmann, R; et al.Dolgopolova, A; Andersen, JCØ; Li, D; Yu, M
Date: 1 February 2018
Ore Geology Reviews
The Weibao Cu-Pb-Zn deposit is typical of skarn deposits in the Qimantagh metallogenic belt (QMB), EastKunlun Mountains, northern Tibetan Plateau. It comprises three ore blocks from west to east, known as Weixi,Main and Weidong. Mineralization in the Weibao deposit is intimately related to Late Triassic intrusions oc-curring at Weixi ...
The Weibao Cu-Pb-Zn deposit is typical of skarn deposits in the Qimantagh metallogenic belt (QMB), EastKunlun Mountains, northern Tibetan Plateau. It comprises three ore blocks from west to east, known as Weixi,Main and Weidong. Mineralization in the Weibao deposit is intimately related to Late Triassic intrusions oc-curring at Weixi and Weidong, and orebodies are predominantly hosted by the Langyashan Formation (marinecarbonate rocks), and to a lesser extent the Devonian volcanic rocks. Skarns from Weixi and Weidong arecharacterized by a high garnet/pyroxene ratio and diopside- and andradite-rich composition of pyroxenes andgarnets, indicating a proximal, oxidized type. In contrast, skarn mineralogy of Main indicates a slightly reducedcondition, typical of Pb-Zn skarn deposits. At least ﬁve hydrothermal mineralization stages can be identiﬁed andthe microthermometric study indicates a general trend of cooling and dilution of the magmatic-hydrothermalﬂuids. Signiﬁcant precipitation of Cu-Fe sulﬁdes commenced from the ﬂuid with the temperature of 340–448 °Cand the salinity of 2.1–15.0 wt% NaCl equiv. Pb-Zn sulﬁdes however mainly precipitated when the temperaturesdeclined to < 370 °C and the salinity declined to < 7.6 wt% NaCl equiv. Carbon, hydrogen and oxygen isotopiccomposition of the ﬂuids suggests a predominantly igneous source for the initial ﬂuids, which were modiﬁedoutward by ﬂuid-rock interaction and mixing with meteoric waters. Both sulfur and lead isotope composition ofsulﬁdes supports a mixed sulfur and metal reservoir consisting of Triassic intrusive rocks and wall rocks.Compared to early skarn-forming and late quartz-carbonate stages, two ore-forming stages show clear evidenceof ﬂuid boiling and ﬂuid-rock interaction. Combined with microthermometric data of ore-forming stages, it canbe deduced that ﬂuid cooling, boiling and ﬂuid-rock interaction were responsible for the signiﬁcant metalprecipitation. The Weibao deposit shows many similarities with skarn deposits in the QMB, and its genetic modeltherefore can be extrapolated to other skarn deposits in this region.
Camborne School of Mines
College of Engineering, Mathematics and Physical Sciences
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