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投稿时间：2016-03-10 修订日期：2016-08-20 网络发布日期：2017-09-06
中文摘要:沙坪沟钼矿床位于大别山北麓的北淮阳构造带，是近年来新发现的特大型斑岩钼矿床。区内燕山期岩浆岩广布，岩性有二长花岗岩、花岗闪长岩、闪长岩、石英正长岩、花岗斑岩、正长花岗岩、隐爆角砾岩等，钼矿床与最晚期的石英正长岩-花岗斑岩成因有关。对最晚期的花岗斑岩体系进行了LA-ICPMS锆石U-Pb定年，结合前人已发表的年代学数据，将区内岩浆岩划分为3个阶段：第一阶段141~133 Ma，主要发育二长花岗岩，具有高Sr、低Y的地球化学特征，形成于加厚下地壳的部分熔融；第二阶段132~125 Ma，包括中基性的含斜长石辉石岩、斜长角闪石岩、闪长岩和酸性的花岗岩、花岗闪长岩等，中基性岩的出现表明地幔物质参与了该阶段岩浆岩的形成，可能与加厚地壳拆沉、软流圈物质上涌有关；第三阶段120~110 Ma，主要发育石英正长（斑）岩和花岗斑岩，为壳源成因。第一阶段岩浆岩的εHf（t）介于-28.3~-22.5，与大别造山带大范围分布的中生代岩浆岩一致，结合前人研究分析表明，沙坪沟第一阶段岩浆岩为类似南秦岭陡岭群片麻岩源区构成的加厚下地壳部分熔融的产物。相比第一阶段岩浆岩，第三阶段石英正长岩、正长花岗岩脉、隐爆角砾岩和花岗斑岩的εHf（t）非常一致，介于-18.4~-13.3之间，与北淮阳千鹅冲钼矿成矿花岗斑岩及汤家坪钼矿成矿花岗斑岩一致，其εHf（t）明显偏高，应为较浅岩浆源区熔融的结果。华南板块广泛分布的古生代富Mo黑色页岩具有和北淮阳成钼矿岩浆岩具有一致的模式年龄，是形成北淮阳钼矿岩浆岩的理想层位。
Abstract:The Shapinggou Mo deposit, located in northern Huaiyang belt of northern Dabie Mountain, is a superlarge porphyric Mo deposit found recently. Yanshanian magmatic rocks are widespread here, which include monzogranite, granodiorite, diorite, quartz syenite, granite porphyry, K-feldspar granite and cryptoexplosive breccia, among which the quartz syenite and granitic porphyry system were last formed and are considered to have had a genetic link to the Mo mineralization. According to LA-ICPMS zircon U-Pb dating for the granitic porphyry system and geochronological data published by previous researchers, the magmatic rocks in the Shapinggou Mo district can be divided into three periods. The first period (141~133 Ma) mainly consists of monzogranite, which is featured by high Sr and low Y geochemical signatures and considered to have been formed from partial melting of thickened lower crust; the second period (132~125 Ma) includes intermediate-mafic rocks such as plagioclase-bearing pyroxenite, plagioclase hornblendite and diorite and acid rocks such as granite and granodiorite with appearence of intermediate-mafic rocks, which indicates a contribution of mantle-derived material in the formation of these rocks, and its formation might have been the results of delamination of thickened lower crust and upwelling of asthenosphere; the third period (120~110 Ma) mainly consists of quartz syenite (porphyry) and granite porphyry, and has a crustal genesis. Zircon εHf(t) of the first period magmatic rocks ranges from -28.3 to -22.5, similar to that of widespread Mesozoic magmatic rocks in Dabie orogen, Comprehensive analysis of these data and previous studies show that the first period rocks were most likely formed by partial melting thickened lower crust similar to things of Douling Group located in South Qinling orogen, whereas the third period magmatic rocks, which include quartz syenite, K-feldspar granite, cryptoexplosive breccia and granite porphyry, have a zircon εHf(t) from -18.4 to -13.3, similar to that of the ore-bearing granite porphyry of Qian'echong and Tangjiaping Mo deposit, obviously higher than that of the first period magmatic rocks, indicating a shallower source. The Paleozoic black shale widespread in South China block are the beneficial source region of ore-forming magmatic rocks of Mo deposits in North Huaiyang belt.
keywords:geochemistry zircon U-Pb dating Hf isotope ore-bearing porphyry Shapinggou Mo deposit northern Huaiyang belt
LIU XiaoQiang,YAN Jun,WANG AiGuo.2017.Characteristics and petrogenesis of Shapinggou ore-bearing porphyry in northern Huaiyang belt[J].Mineral Deposits36(4):837~865