北淮阳沙坪沟钼矿床成矿斑岩体特征与成因

发布时间：2018-03-30 14:43

本文选题：地球化学　切入点：锆石U-Pb年龄　出处：《矿床地质》2017年04期

【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ε_(Hf)(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ε_(Hf)(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ε_(Hf)(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 molybdenum deposit is located in the northern Huaiyang tectonic belt at the northern foot of the Dabie Mountains. It is a newly discovered super-large porphyry molybdenum deposit in recent years. The Yanshanian magmatic rocks are widely distributed in the area, with lithologic features of monzogranite, granodiorite, diorite and quartz syenite. Granitic porphyry, syenite, crypto-explosive breccia and molybdenum deposits are related to the genesis of the late quartz syenite and granitic porphyry. The LA-ICPMS zircon U-Pb dating of the late granitic porphyry system is carried out. The magmatic rocks in the area are divided into three stages: the first stage is 141T 133Ma.The first stage is mainly composed of monzogranites with high Sr and low Y geochemical characteristics and formed in the partial melting of the thickened lower crust; The second stage, 132- 125 Ma, includes plagioclase pyroxenite, plagioclase diorite, diorite and acidic granite, granodiorite, etc. The occurrence of meso-basic rocks indicates that mantle material is involved in the formation of magmatic rocks at this stage. It may be related to the thickening of the crust and the upwelling of the asthenosphere material. In the third stage, 120-110 Ma, quartz syenite (porphyry) and granitic porphyry are mainly developed. The first stage of magmatic rocks is between -28.3mg-22.5, which is consistent with the Mesozoic magmatic rocks distributed in large scale in the Dabie orogenic belt. Combined with the analysis of previous studies, it is shown that, in the first stage, the magmatic rocks in the first stage are of the same order as the Mesozoic magmatic rocks in the Dabie orogenic belt. The first stage of Shapinggou magmatic rock is the product of partial melting of thickened lower crust, similar to the gneiss source area of the South Qinling steep Ridge Group. Compared with the first stage magmatic rock, the third stage quartz syenite, syenite vein, etc. Cryptoexplosive breccia and granitic porphyry are consistent with each other in the range of -18.4 ~ 13.3, which is consistent with the ore-forming granitic porphyry of Qianyichong molybdenum deposit and Tangjiaping molybdenum deposit in North Huaiyang. The Mo-rich black shale widely distributed in the South China plate has the same model age as the molybdenum magmatic rocks of the North Huaiyang molybdenum deposit, which is the ideal horizon for the formation of the magmatic rocks of the North Huaiyang molybdenum deposit.
【作者单位】：合肥工业大学资源与环境工程学院;中国地质调查局南京地质矿产研究所;
【基金】：国家自然科学基金资助项目(编号:41272074) 中国地质调查局地质矿产调查评价专项(编号:12120113067800)联合资助的成果
【分类号】：P618.65

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