豫西南泥湖矿集区石宝沟花岗岩体的锆石U-Pb年龄、岩石地球化学及Hf同位素组成

杨阳; 王晓霞; 柯昌辉; 李金宝

豫西南泥湖矿集区石宝沟花岗岩体的锆石U-Pb年龄、岩石地球化学及Hf同位素组成

Zircon U-Pb age, geochemistry and Hf isotopic compositions of Shibaogou granitoid pluton in the Nannihu ore district, western Henan Province

摘要

摘要: 提要：石宝沟花岗岩体位于华北陆块南缘，主要由似斑状二长花岗岩和中细粒二长花岗岩组成，发育岩浆暗色包体。LA-ICPMS锆石U-Pb定年结果显示，似斑状二长花岗岩和中细粒二长花岗岩的成岩年龄分别为（156±1）Ma (N=15，MSWD=0.34)和（157±1）Ma(N=17，MSWD=0.10)。这些花岗岩的A/CNK=0.82～1.02，Na2O+K2O =7.61%～8.91%，K2O/Na2O=1.02～1.48，属于高钾钙碱性、准铝质-弱过铝质I型花岗岩。稀土和微量元素特征显示其富集LREE、Rb、Ba、K、Pb 等大离子亲石元素，亏损HREE、P、Ti 等高场强元素，具有弱的负铕异常，个别样品具有正铕异常（δEu＝0.81～1.12）。似斑状二长花岗岩的锆石εHf(t)为-22.6～-8.3，tDM2为2.64～1.73Ga；中细粒二长花岗岩εHf(t)为-26.9～-12.4，tDM2为2.91～1.99Ga。岩石地球化学和锆石Hf同位素组成特征表明，石宝沟花岗岩体的源区物质以壳源物质为主，可能为太古宙太华群，但也有年轻幔源组分的参与。

Abstract: Abstract：The Shibaogou granitoid pluton, consisting of porphyritic monzogranite and middle-fine-grained monzogranite as well as mafic magma enclaves, is located in the southern margin of the North China Craton. The zircon LA-ICPMS dating of the porphyritic monzogranite and mid-fine-grained monzogranite from this pluton yielded ages of 156±1Ma (MSWD=0.34, N=15) and 157±1Ma (MSWD=0.10, N=17), respectively. The rocks are of high K calc-alkaline series and belong to metaluminous to weak peraluminous I-type granite with A/CNK being 0.82～1.02, Na2O+K2O 7.61%～8.91% and K2O/Na2O 1.02～1.48. Their REE and trace elements are enriched in large ion lithophile elements (LREE, Rb, Ba, K and Pb), and depleted in high-field strength elements (HREE, P and Ti), with slightly negative to positive anomalies of Eu (δEu＝0.81～1.12). Zircon Hf isotopic compositions of the porphyritic monzogranite and middle-fine-grained monzogranite are mainly characterized by εHf(t) values of -22.6～-8.3 and -26.9～-12.4, and the two-stage model ages of 2.64 to 1.73 Ga and 2.91 to 1.99 Ga, respectively. Geochemistry and zircon Hf isotopic compositions show that they were derived from an ancient continental crust (probably Archean Taihua Group), with the addition of juvenile components.

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