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川西甲基卡地区侏倭组沉积物源分析—来自碎屑锆石U-Pb年龄证据
投稿时间:2019-07-09  修订日期:2019-09-06  点此下载全文
引用本文:
DOI:10.19762/j.cnki.dizhixuebao.2020021
摘要点击次数: 34
全文下载次数: 41
作者单位E-mail
秦宇龙 稀有稀土战略资源评价与利用四川重点实验室、四川省地质调查院 成都 63328712@qq.com 
李名则 稀有稀土战略资源评价与利用四川重点实验室、四川省地质调查院 成都  
熊昌利 稀有稀土战略资源评价与利用四川重点实验室、四川省地质调查院 成都  
詹涵钰 稀有稀土战略资源评价与利用四川重点实验室、四川省地质调查院 成都  
徐云峰 稀有稀土战略资源评价与利用四川重点实验室、四川省地质调查院 成都  
武文辉 稀有稀土战略资源评价与利用四川重点实验室、四川省地质调查院 成都  
李峥 稀有稀土战略资源评价与利用四川重点实验室、四川省地质调查院 成都  
基金项目:四川省科技计划项目(编号2018SZ0276),全国陆域及海区地质图件更新与共享(DD20190370),中国地质调查项目(DD20160074、12120113049500)资助
中文摘要:松潘—甘孜造山带是青藏高原东北部的重要组成单元,是华北板块、扬子板块和羌塘块体的主要汇聚地区,主要由中生代浅变质沉积地层和一系列岩浆岩组成,记录了印支期以来块体之间的收敛汇聚等构造活动。其中,雅江残余盆地发育一套厚度巨大的中生代碎屑岩沉积序列和岩浆岩,是研究松潘-甘孜造山带地质构造演化的理想地区之一。本文对川西甲基卡地区侏倭组的样品进行了碎屑锆石LA-ICP-MS U-Pb年龄测试,碎屑锆石U-Pb年龄存在四个峰值,分别为231~281Ma、424~502Ma、707~983Ma、1539~1850Ma,表明扬子克拉通西缘及松潘甘孜造山带南部至少经历了四期强烈的构造—岩浆热事件,这四期事件在三叠系沉积地层中有非常清楚的记录。231~281Ma的锆石来自东昆仑,这一年龄段的锆石最可能来自北部晚二叠世松潘洋向北俯冲于华北板块之下所形成的东昆仑岛弧花岗岩。424~502MaMa的锆石来自北秦岭,代表了加里东期南秦岭与北秦岭和华北板块的拼合事件。722~983Ma的锆石来自扬子板块,这一年龄段的锆石最可能来自盆地东部新元古界拉伸系上扬子克拉通盆地向北西俯冲于华北板块之下所形成的南秦岭花岗岩,形成于扬子板块晋宁期陆壳增生事件。1539~1850Ma与华北板块基底年龄特征值正相对应,是吕梁期华北克拉通东西两大块体在中部发生碰撞,华北古陆进一步固结、扩大的时间,这其中包含了继承东西块体的太古宙物质和新生的火成岩和沉积岩,在中-晚三叠世,随着秦岭洋的关闭和碰撞造山,将大量碎屑物质经华北板块南缘东西向的疏导体系注入松潘甘孜盆地。说明松潘甘孜三叠纪复理石盆地侏倭组主要接受来自东昆仑、华北板块和秦岭造山带的物质。最年轻碎屑锆石可以限定沉积岩的最大沉积年龄,侏倭组4颗年轻碎屑锆石加权平均计算得出241.8±4.5Ma(n=4),推测侏倭组沉积年龄介于231.6~249.9Ma之间。
中文关键词:碎屑锆石  U-Pb年龄  川西甲基卡地区  侏倭组  松潘-甘孜造山带
 
Depositional Origin of Zhuwo Formation in Jiajika Region, Western Sichuan Province: Evidence from Detrital Zircon U-Pb Age
Author NameAffiliationE-mail
Qin Yulong Evaluation and Utilization of Strategic Rare Metals and Rare Earth Resource Key Laboratory of Sichuan Provincn,Sichuan Geological Survey 63328712@qq.com 
Li Mingze Evaluation and Utilization of Strategic Rare Metals and Rare Earth Resource Key Laboratory of Sichuan Provincn,Sichuan Geological Survey  
Xiong Changli Evaluation and Utilization of Strategic Rare Metals and Rare Earth Resource Key Laboratory of Sichuan Provincn,Sichuan Geological Survey  
Zhan Hanyu Evaluation and Utilization of Strategic Rare Metals and Rare Earth Resource Key Laboratory of Sichuan Provincn,Sichuan Geological Survey  
Xu Yunfeng Evaluation and Utilization of Strategic Rare Metals and Rare Earth Resource Key Laboratory of Sichuan Provincn,Sichuan Geological Survey  
Wu Wenhui Evaluation and Utilization of Strategic Rare Metals and Rare Earth Resource Key Laboratory of Sichuan Provincn,Sichuan Geological Survey  
Li Zheng Evaluation and Utilization of Strategic Rare Metals and Rare Earth Resource Key Laboratory of Sichuan Provincn,Sichuan Geological Survey  
Abstract:The Songpan-Ganzi orogenic belt is an important part of northeastern Qinghai-Tibet Plateau. It is the major convergent region of North China block, Yangtze block and Qiangtang block. The orogenic belt consists of Mesozoic low-grade metamorphic strata and a series of magmatic rocks, and has recorded convergent events of the three blocks since Indosinian Period. Yajiang remnant basin within the orogenic belt, in which an extremely thick sedimentary series and wide spread magmatic rocks occur, is an ideal region for the research of tectonic evolution of Songpan-Ganzi orogenic belt. This paper conducts a research on detrital zircon LA-ICP-MA U-Pb geochronology. The results show that the zircon U-Pb age values focus on four peaks, 231-281Ma, 424-502 Ma, 707-983Ma, 1539-1850Ma, respectively, indicating that the west margin of Yangtze craton and Songpan-Ganzi orogenic belt have been subject to at least four stages of intensive tectonic-magmatic events, which were recorded in the Triassic strata in the area. The zircons with ages 231-281 Ma are most probably from the arc granites of east Kunlun Mountains, formed during subduction of Permian Songpan-Ganzi Ocean downward to North China block. The zircons with ages 424-502Ma derive from Yangtze block, representing a splicing event of south Qinling, north Qinling and North China block. The zircons with ages 722-983Ma are from the Yangtze block, and most probably from the granites of south Qinling formed during the subduction of Neoproterozoic extensional upper Yangtze craton basin below the North China block. The granites are the products of crust growth event in Jinning period. The ages 1539-1850 Ma correspond to that of basement of North China block, when east part and west part of North China craton collided in the central area and the North China paleo-continent was in the process of further solidification and extension. The Archean material and newly generated igneous and sedimentary rocks were inherited, and a great many of these detrital materials were carried into Songpan-Ganzi basin through an east-west direction transport system during the closure and collisional orogeny of south Qinling Ocean in Middle-Late Triassic Epoch. Our results suggest that origin of the Triassic Xinduqiao Formation of Songpan-Ganzi flysch basin was mainly the materials from east Kunlun Mountains, North China block and Qinling orogenic belt. The youngest detrital zircons can limit the oldest depositional age. The weighted average age of four youngest zircons is 241.8±4.5 Ma, temporally constraining the deposition event of sedimentary rocks.
keywords:Detrital zircon  U-Pb age  Jiajika area, Western Sichuan Province  Zhuwo Formation  Songpan-Ganze orogenic belt
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