徐淮地区早白垩世闪长岩类继承锆石U-Pb年代学及地质意义  

Inherited zircon U-Pb chronology and geological significance of the Early Cretaceous diorites in Xuhuai area

作　　者：产思维 Chan Siwei(Anhui Exploration Technology Institute,Hefei 230031,Anhui,China)

机构地区：[1]安徽省勘查技术院,安徽合肥230031

出　　处：《地质学刊》2020年第3期258-264,共7页Journal of Geology

基　　金：安徽省公益性地质项目“徐宿弧(安徽段)金多金属矿成矿背景调查”(2016-g-3-34)。

摘　　要：对徐淮地区前欧盘和徐楼岩体进行了镜下显微研究和锆石U-Pb定年,结果表明二者均为早白垩世闪长玢岩,前者形成于(126.4±2.1)Ma,后者形成于(127.9±2.0)Ma,与该区其他岩体成岩年龄基本一致。徐淮地区早白垩世中酸性侵入岩形成于伸展构造背景中,是燕山期中国东部大规模构造-岩浆事件的产物。在岩体中发现了多颗不同时代的继承锆石,其中前欧盘闪长玢岩3颗新元古代继承锆石加权平均年龄为(2512±60)Ma;徐楼闪长玢岩1颗新元古代继承锆石年龄为(2556±57)Ma,3颗古元古代继承锆石加权平均年龄为(1815±210)Ma。约2.5 Ga和1.8 Ga继承锆石的发现,表明徐淮地区存在古元古—新太古代基底,并且发生过约2.5 Ga和1.8 Ga构造热事件。类比研究表明,徐淮地区具备寻找受构造控制的热液型金矿和斑岩型金、钼矿床的地质条件。Microscopic studies and zircon U-Pb dating of the Qian′oupan and Xulou rock masses in Xuhuai area show that both of them are early Cretaceous diorite porphyrite,with the former formed at(126.4±2.1)Ma and the latter at(127.9±2.0)Ma,which are basically consistent with the diagenetic ages of other rock masses in Xuhuai area.Early Cretaceous intermediate-acid intrusive rocks in Xuhuai area were formed in extensional tectonic setting and were the product of large-scale tectono-magmatic events in eastern China during the Yanshanian Period.Several inherited zircons of different ages were found in the rock mass,among which 3 Neoproterozoic inherited zircons of Qian'oupan diorite porphyrite had a weighted average age of(2512±60)Ma.One Neoproterozoic inherited zircon from Xulou diorite porphyrite was(2556±57)Ma,and the three Paleoproterozoic inherited zircons had a weighted average age of(1815±210)Ma.The discovery of zircons inherited by about 2.5 Ga and 1.8 Ga indicates that there is a Paleoproterozoic-Neoarchean basement in Xuhuai area,and there are tectonothermal events of about 2.5 Ga and 1.8 Ga.The analogical study shows that there are geological conditions for finding hydrothermal gold deposits and porphyry gold-molybdenum deposits controlled by structure in Xuhuai area.

关 键 词：闪长岩类 继承锆石 U-PB年代学 徐淮地区 

分 类 号：P697.3[天文地球—地质学]