摘要
英城子金矿床位于佳木斯地块西缘、张广才岭东侧,是一个与韧性剪切带有关的金矿床。本文首次对矿区内出露的大面积黑云母碱长花岗岩,进行了锆石LA-ICPMSU-Pb年代学精细研究。实验共获得四组单颗粒锆石U-Pb谐和年龄,它们分别为612±4Ma、495.2±2.7Ma、476.8±5.5Ma和431±3Ma;其中612±4Ma的年龄值指示晚元古代地壳增生过程形成的花岗岩锆石特征,495.2±2.7Ma的年龄值与区域内麻山群的变质作用时间相吻合,431±3Ma的年龄值与早古生代晚期的区域变质作用时间吻合,而476.8±5.5Ma的年龄值则代表黑云母碱长花岗岩的真实结晶年龄。这项成果记录了该地区在中-新元古代时期曾发生过重要的地壳增生事件,增生后的地壳被打开形成大洋;至早古生代早期,两侧的地体发生拼贴,引起区域麻山群麻粒岩相的变质作用、形成花岗质片麻岩;到早古生代晚期,佳木斯地块西缘的陆间洋最终闭合,形成具有壳源特征的同碰撞花岗岩,此后发生的韧性变形作用可能为金矿床的形成提供了有利条件。
The Yingchengzi gold deposit located at the western Jiamusi massif and the eastern Zhangguangcailing area is a deposit related to shearing zone. This study firstly carried out research by zircon LA-ICP MS U- Pb dating on the widely exposed biotite alkali-feldspar granite in the area. The analysis yielded four sets of U-Pb concordant ages for single zircons： 612±4Ma,495.2±4-2.7Ma,476.8±5.5Ma and 431±3Ma by LA- ICP MS. The age of 612±4Ma presents the characteristics of granitic zircon formed during the process of late Proterozoie crustal growth; the age of 495.2 ± 2. 7Ma is consistent with the time of Mashan Group metamorphism and the age of 431±3Ma with the regional metamorphism in the late Paleozoic; the zircon age of 476.8±5.5Ma represents the real crystallization age of the biotite alkali-feldspar granite. The result records the important event of crustal growth ever occurring during the mid-late Proterozoic, and the new crust was opened to form an ocean. Until the early Early Paleozoic, the terrenes between the ocean were collided and aroused granulite facies metamorphism with the Mashan Group in the area. In the late Early Paleozoic, the intercontinental ocean was finally closed, forming syn collisional granite in the western Jiamusi massif, which shows the features of crustal source. Since then, the ductile deformation with the collision offered some advantages for the formation of gold deposits.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2009年第9期1327-1334,共8页
Acta Geologica Sinica
基金
国家自然科学基金项目(批准号:40472050
40772052)
黑龙江省地球物理勘察院项目(编号:3J106H424422)资助的成果
