黑龙江陈家店金矿区花岗斑岩锆石U-Pb定年、地球化学特征及地质意义

对黑龙江陈家店金矿区内花岗斑岩进行LA-ICP-MS锆石U-Pb定年及元素地球化学研究。测年结果显示,花岗斑岩锆石~(206)Pb/~(238)U加权平均年龄为(227±4)Ma。岩石地球化学特征显示,花岗斑岩具有富Si、富Al、富碱质和低Mg、低Ca的特征;微量元素表现出高场强元素(HFSE)Th、Rb和K明显富集,而大离子亲石元素(LILE)Ba、Sr和Ti明显亏损的特点;稀土元素以明显的轻稀土元素富集重稀土元素相对亏损为特征,轻、重稀土元素分馏程度较强(La/Yb)_N=0.47~4.99,有强烈的Eu负异常(δEu=0.08~0.68)。构造判别图解显示,花岗斑岩具有碰撞后花岗岩特征,形成于碰撞后的构造环境。综合研究认为,矿区花岗斑岩的成因类型为S型花岗岩,其成岩时代为晚三叠世,形成于古亚洲洋闭合后的陆陆碰撞造山环境,地处火山弧形构造带,属于安第斯型大陆边缘。

Zircon U-Pb dating,geochemical characteristics and geological significance of granite porphyry in Chenjiadian gold deposit of Heilongjiang

The authors undertook zircon LA-ICP-MS U-Pb dating and studied the granite porphyry in geochemistry in Chenjiadian gold deposit of Heilongjiang. The age dating results show that the zircons from the granite porphyry yielded a 206Pb/238U weighted mean age of (227±4)Ma. The geochemical characteristics of granite porphyry show that it is enriched in Si, Al and alkali, but depleted in Mg and Ca. The trace elements for granite porphyry are obviously enriched in HFSE (Th, Rb, K) and depleted in LILE (Ba, Sr, Ti), and rare elements show LREE-enriched, HREE-depleted, strong fractionation of LREE/HREE (La/Yb]N=0.47~4.99) and strong negative anomaly of Eu (δEu=0.08~0.68). The discrimination diagrams indicate the granite porphyry is characterized by post-collision, which formed in post-collisional tectonic setting. Comprehensive results show the granite porphyry belongs to granite in S-type, formed in the orogenic setting of continental-continental collision after the closure of Paleo-Asian Ocean in Late Triassic. The Chenjiadian gold deposit is located in volcanic arc tectonic belt belongs to the Andean continental margin.