The Kaladaban Volcanogenic Massive Sulfide-Type Pb-Zn Deposit in northern Altun Mountains, NW China
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Institute of Geomechanics, Chinese Academy of Geological Sciences

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    Abstract:

    The volcanogenic massive sulfide (VMS) type deposit has received much attention in the past years. As the largest PbZn deposit in the LapeiqunHongliugou AuCuFe and polymetallic metallogenic belt of northern margin of Altun Mountains, the Kaladaban PbZn deposit is located within the area sandwiched between the NEstriking Altun strikeslip fault and EWstriking northern Altun fault. Near EWtrending volcanicsedimentary rocks of lower Zhuo’abulake Formation of Ordovician System crop out in the mining area, characterized by a monocline with mediumangle northward dipping at 30~58. The PbZn metallization is controlled by a specific stratigraphic horizons of volcanicsedimentary rocks; in other words, all PbZn orebodies occur in the intermediatefelsic volcanic rocks of the 4th member of Zhuo’abulake Formation (i.e. rhyolite, dacitic lava and dacitic crystal tuff). The ore bodies are of stratiform or stratiformlike features with stable occurrence and large extension. The largest PbZn orebody extends more than 2400m along trending direction and more than 900m’s extension along dipping depth. The useful components of the ore are mainly Pb and Zn with associated elements of Cu, Au, Ag and S. The main alteration is pyritization, silicification and sericitization, with jarositization and limonitization occurring in the oxidized zone of the surface. The average Pb isotopic compositions of 12 samples from the deposit are 208Pb/204Pb=381169, 207Pb/204Pb=156278 and 206Pb/204Pb=184684, which indicates that the Pb of the ores came from the mixture of the upper crust and orogenic belt. The average 34S values of 15 samples (+828‰) suggest a mixed marine sedimentary and magmatic sulfur source. The chondritenormalized REE distribution patterns of the PbZn ore are similar to that of the intermediatefelsic volcanic rock in the ore district and in the Kaladawan area, showing that the ore and orebearing intermediatefelsic volcanic rock are of the same origin. The trace elements compositions of the ore present negative anomalies of Nb and Ta, and positive anomaly of Ba, indicating addition of marine sedimentary and an islandarc metallogenic tectonic setting. Zircon SHRIMP UPb dating yields an age of 482~485Ma for the orebearing volcanic rock, reflecting that the PbZn mineralization formed in early Ordovicianf early Paleozoic era. Geological and geochemical characteristics of the Kaladaban PbZn deposit indicates that the PbZn deposit belongs to the volcanogenic massive sulfide type (VMStype). Therefore, the metallogenic process can be summed up as follows. In early Ordovician epoch of early Paleozoic era, southward subduction of the north Altun plate resulted in partial melting of oceanic crust in footwall, overlying marine sediments, and continental crust of hanging wall, forming intermediatefelsic islandarc magma. At the late stage of magma eruption, residual magma rich in Pb and Zn material was gradually formed. Volcanogenic massive sulfide PBZn deposit was finally formed in company with eruption of magma rich in PbZn. The VMStype PbZn deposit is the most important prospecting target and deposit type in the Kaladawan area on the northern margin of Altun Mountains, and the western part of the VMStype mineralization belt should be the prospecting target area.

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CHEN Bailin, QI Wanxiu, CUI Lingling, CHEN Zhengle, LIU Bing, ZHAO Lei, JIANG Rongbao, HAN Fengbin, LI Li, LIU Rong.2017. The Kaladaban Volcanogenic Massive Sulfide-Type Pb-Zn Deposit in northern Altun Mountains, NW China[J]. Acta Geologica Sinica,91(8):1818-1835

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History
  • Received:May 09,2016
  • Revised:July 27,2016
  • Adopted:August 16,2017
  • Online: August 18,2017
  • Published: