山东牟平院格庄岩体锆石U-Pb年龄及其对周缘铜钼多金属成矿的制约

邹键; 唐文龙; 丁正江; 薄军委; 李志强; 于森

doi:10.12029/gc20210316

山东牟平院格庄岩体锆石U-Pb年龄及其对周缘铜钼多金属成矿的制约

Zircon U-Pb dating of the Yuangezhuang pluton in Muping of Shandong Province and its constraints on mineralization of Cu-Mo deposits

摘要

摘要: 牟平院格庄岩体位于胶东东部，为燕山晚期形成的与斑岩型-矽卡岩型铜钼多金属矿床有关的岩体之一。获得院格庄岩体崖西、后野、西上寨3个单元二长花岗岩LA-ICP-MS锆石U-Pb定年结果分别为（118.10±0.66）Ma、（118.52±0.78）Ma、（118.80±0.67）Ma，皆为早白垩世晚期。岩石地球化学研究表明：岩石属于高钾钙碱性、准铝质系列（K₂O/Na₂O值为1.00~1.29、A/CNK=0.98~1.02）。轻重稀土元素分馏明显（（La/Yb）_N=26.91~35.75），δEu=0.84~0.93，具弱负铕异常。高场强元素Nb、Ti、P元素强烈亏损，大离子亲石元素Rb、K、U富集。地球化学特征显示院格庄岩体为I型花岗岩，为壳幔同溶型花岗岩。该岩体对其周缘铜钼矿空间分布和成矿时代有显著的制约作用，具有铜钼多金属矿的成矿专属性。

Abstract: The Yuangezhuang Pluton located in the east of Jiaodong area,is formed in the late Yanshanian and is one of the granites associated with Cu-Mo polymetallic deposits hosted inporphyry and skarn. LA-ICP-MS zircon U-Pb dating of Yaxi unite,Houye unite and Xishangzhai unite from the Yuangezhuang monzonitic granite yields (118.10±0.66) Ma,(118.52±0.78) Ma,and (118.80±0.67) Ma respectively,indicating the Late Epoch of Early Cretaceous. The results of petrochemistry indicate the pluton is belong to high-K calc-alkaline serie (K₂O/Na₂O=1.00-1.29,A/CNK=0.98-1.02). The results of trace elements are characterized by dramatic fractionation between light REE and heavy (REE(La/Yb)_N=26.91~35.75 unapparent Eu anomalies (δEu=0.84-0.93),enriched in LILE (i.e. Rb,K,U) and loss in HSFE (i.e. Nb,Ti,P). The geochemical characteristics indicate the Yuangezhuang pluton is an I type granite,crust-mantle syntectic granite. The pluton has strong constrain on spatial distribution and metallogenic epoch of Cu-Mo deposits.

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