河南东沟钼矿花岗斑岩成因:岩石地球化学、锆石U-Pb年代学及Sr-Nd-Hf同位素制约

Petrogenesis of the granitic porphyry related to the giant molybdenum deposit in Donggou,Henan province,China:Constraints from petrogeochemistry,zircon U-Pb chronology and Sr-Nd-Hf isotopes

本研究对东沟超大型钼矿床的成矿母岩-东沟花岗斑岩开展了系统的年代学、岩石地球化学及Sr-Nd-Hf同位素分析工作。LA-ICP-MS锆石U-Pb定年结果表明,东沟花岗斑岩成岩年龄为114～117Ma,与已有的成矿年龄(116±2Ma,Re-Os法)一致,证实了东沟钼矿为一斑岩型矿床。详细的岩石地球化学分析显示东沟花岗斑岩岩体与区域上太山庙大型花岗岩基为同源演化关系,它们均为弱过铝质,具有富Si、富K、富Rb、Th、U等大离子亲石元素、富Nb、Ta、Zr、Hf等高场强元素,贫Fe、Mg、Ca,贫Sr、Ba,Ga/Al比值较高等地球化学特征,属铝质A型花岗岩,形成于伸展构造体制,东沟岩体是母岩浆经历了强烈结晶分异高度演化的产物;东沟岩体Nd同位素组成为0.51166～0.51182,ε_(Nd)(t))值在-17.3～-14.3之间,锆石的ε_(Hf)(t)值变化较大,由-3.4至-18.7,另有一颗年龄为1715Ma的捕获锆石的ε_(Hf)(t)值为-2.4,Nd、Hf模式年龄分别为1.5～1.8Ga与1.3～1.7Ga。我们认为东沟岩体的岩浆源区以古老地壳物质为主,但也有少量幔源组分参入,并且幔源物质的加入及很高的岩浆演化程度可能对东沟钼矿的成岩成矿过程具有重要作用。

In this study,we carried out a comprehensive research including zircon U-Pb dating,petrogeochemistry and Sr-Nd-Hf isotope analysis on the granitic porphyry related to the giant molybdenum deposit in Donggou,Henan Province,China.LA-ICP-MS zircon U-Pb chronology indicated that the Donggou porphyry emplaced at 114～117Ma,identical with the time when the molybdenum deposit were formed(116±2Ma,Re-Os age).Both the Donggou porphyry and the large Taishanmiao batholith to its south are enriched in Si,K,LILEs such as ...