Abstract:The Changba-Lijiagou lead-zinc deposit, one of the major lead-zinc deposits in China, lies in the east of the Xicheng Iead-zinc ore field and is the largest and richest deposit in it. Located in Lixian-Zashui Variscan miogeosynclinal fold belt, the deposit is in a paleogeographical environment of semi-closed marine basin. The host rocks are upper member of the Middle Devonian Qingshuigou Formation, which corresponds to the 2nd layer of the 6th lithological member of Middle Devonian Xihanshui Group defined by the former Regional Survey Party and is composed of a suite of neritic clastic-carbonate formation that underwent medium-grade metamorphism. The ore district is situated on the northeast wing (Fig. 1, an inverted monoclinic stratum) of the Wujiashan anticline, characterized by lots of NE-and NWW-trending fractures and intensely-developed magmatic activities. There exist mainly six orebodies which occur respectively in marble, crystalline limestone and biotite quartz schist and are conformable with the host rocks in stratoid forms (Figs. 2 and 3). Ore nunerals are rather simple with galena, sphalerite and pyrite as the main constituents; gangue minerals are chiefly quartz, calcite and barite. Ore possesses 8-12% Pb+Zn and has striped-laminated, massive and aphanitic colloid banded structures. The associated useful components are Ga, Ge, Cd, In, Tl and Ag and harmful components are As and Sb. Wallrock alterations are weak. Geochemically, sulfur isotopes are characterized by an enrichment in heavy sulfur with δ34S values being 7.1-27.81‰ (Fig. 4); lead in the ore is normal lead and U-Pb ages fall within 293-508 Ma; δ18O and δ13C values of calcite from ore and marble are close to those of Devonian marine facies carbonate rocks; Inclusions in minerals, mostly of gaseous phases, are less in quantity and small in size and belong to Na+-Cl--SO-2 type brine, with the homogenization temperature being 90-318℃(Fig, 5). Concerning the genesis of this deposit, there have been proposed various hypotheses, such as magmatic-hydrothermal mineralization, sedimentary-metamorphism, hot-brine ore formation, sedimentary-metamorphism with magmatic-hydrothermal superimposition and volcanic-hot brine exhalative sedimentary-metamorphism. The authors consider that it should belong to hot brine sedimentary-reformation type stratabound deposit.
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杨松年, 缪远兴.1986.厂坝-李家沟铅锌矿床地质特征[J].矿床地质,5(2):14~23.1986.Geological Characteristics Of The Changba-Lijiagou Lead-Zinc Deposits In Gansu Province[J].Mineral Deposits5(2):14~23
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