摘要
塔里木板块北缘额济纳旗老硐沟金矿床发育系列蚀变中基性岩脉,其形成时代与成因对制约金成矿作用及区域古亚洲洋的演化提供了研究窗口。本文在老硐沟金矿区Ⅱ矿段采集系列辉绿岩脉及与金成矿相关的蚀变闪长玢岩脉样品,进行了锆石LA-ICP-MS U-Pb定年、Hf同位素组成和全岩元素分析。结果表明,辉绿岩脉和闪长玢岩脉侵位时代分别为(286.5±1.7)Ma和(243.2±1.1)Ma,即早二叠世和中三叠世,二者年龄先后顺序与野外观察的交切关系相符。根据金矿体穿插闪长玢岩脉的特征,限定金成矿时代略晚于243 Ma。辉绿岩脉锆石εHf(t)为-3.67~0.97,全岩元素组成表现为准铝质钙碱性系列,反映岩浆源区既有新元古代新生地壳组分,又有中元古代古老地壳组分。蚀变闪长玢岩脉εHf(t)=-0.07~-4.76,全岩元素组成是过铝质钾玄岩系列(富钾特征受到矿区钾化蚀变的影响),指示其岩浆主要源于中元古代的地壳物质熔融。综合塔里木地块北缘晚古生代至早中生代构造演化史,提出晚石炭世—早二叠世北山地区古洋盆消减,洋壳俯冲导致地幔楔部分熔融,岩浆上侵至浅部断裂冷却形成辉绿岩脉;早二叠世末期北山地区进入陆内演化阶段,中三叠世产生造山后伸展作用,导致中元古代的地壳物质发生减压熔融,岩浆沿地壳断裂上侵、就位形成闪长玢岩脉。
The formation age and genesis of the altered intermediate bedrock dike in the Laodonggou gold depo-sit(Ejin Banner,northern margin of Tarim terrane)provide a window to study the gold mineralization constraints and the Paleo-Asian Ocean evolution.In this study,a series of gold ore-related diabase dike and altered diorite porphyrite dike samples were collected from the Laodonggou ore section II,on which we conducted LA-ICP-MS zircon U-Pb dating,Hf isotope and whole-rock geochemical analyses.The results showed that the emplacement of diabase dikes and diorite porphyrite dikes occurred in the Early Permian(286.5±1.7 Ma)and Middle Triassic(243.2±1.1 Ma),respectively,and such age sequence is consistent with the observed field crosscutting relationship.According to the characteristics of diorite porphyrite dikes interlaced with gold orebo-dies,the gold mineralization is suggested to be slightly after 243 Ma.ZirconεHf(t)value of the diabase dikes ranges from-3.67 to 0.97,and the whole-rock element composition shows that the rocks are peraluminous calc-alkaline.This indicates that the magma source region contains both Neoproterozoic juvenile crustal components and Mesoproterozoic ancient crustal components.Altered diorite porphyrite dikeεHf(t)=-0.07 to-4.76,and the whole-rock element composition is the peraluminous K-rich basalt series(K-rich characteristics affected by the potassic alteration in the mining area),indicating that the magma is mainly derived from the Mesoproterozoic crustal melting.Based on the Late Paleozoic to Early Mesozoic tectonic evolution in the northern margin of the Tarim block,we proposed that the Late Carboniferous-Early Permian paleo-oceanic basin subduction in the Beishan region may have led to partial melting of the mantle wedge,and that the magma may have ascended into shallow faults and cooled to form diabase dikes.In the end Early Permian,the Beishan region entered an intracontinental tectonic stage,and post-orogenic extension occurred in the Middle Triassic.This likely resulted in the decompression and melting of Mesoproterozoic crustal materials,and magma emplacement along crustal faults to form diorite porphyrite dikes.
作者
薛仲凯
范堡程
黄豪擎
唐卫东
葛战林
李朋伟
胡建辉
杨晓奇
郭永超
李空
XUE Zhongkai;FAN Baocheng;HUANG Haoqing;TANG Weidong;GE Zhanlin;LI Pengwei;HU Jianhui;YANG Xiaoqi;GUO Yongchao;LI Kong(Xi’an Center of Mineral Resources Survey,China Geological Survey,Xi’an,Shaanxi 710100,China;Xi’an Center of Geological Survey,China Geological Survey,Xi’an,Shaanxi 710054,China;State Key Laboratory of Geohazard Prevention and Geoenvironment Protection,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Research Center of Applied Geology of China Geological Survey,Chengdu,Sichuan 610036,China;Langfang Comprehensive Survey Center of Natural Resources,China Geological Survey,Langfang,Hebei 065000,China;School of Geophysics,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Ejina Banner Yuantong Mining Co.,Ltd.,Ejina Banner,Inner Mongolia 735400,China;School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China)
出处
《现代地质》
CAS
CSCD
北大核心
2023年第3期627-644,共18页
Geoscience
基金
中国地质调查局项目“秦岭成矿带金矿资源潜力动态评价”(DD20220975)
“全国金矿资源潜力评价”(ZD20220318)
“北山地区月牙山合黎山一带萤石铜钼矿调查评价”(DD20211552)。
