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东准噶尔卡拉麦里地区碱性玄武岩年代学、地球化学特征及其构造意义
投稿时间:2020-05-10  修订日期:2020-07-25  点此下载全文
引用本文:
DOI:10.19762/j.cnki.dizhixuebao.2020281
摘要点击次数: 112
全文下载次数: 138
作者单位地址
李海 长安大学地球科学与资源学院 陕西省西安市雁塔区育才路126号,长安大学地球科学与资源学院
李永军 长安大学地球科学与资源学院 
徐学义 中国自然资源航空物探遥感中心 
杨高学 长安大学地球科学与资源学院 
王祚鹏 长安大学地球科学与资源学院 
徐倩 长安大学地球科学与资源学院 
王龙江 长安大学地球科学与资源学院 
基金项目:国家重点研发计划专项“天山–阿尔泰增生造山带大宗矿产资源基地深部探测技术示范”项目(2018YFC0604000)、新疆中央返还两权价款资金项目(Y15-1-LQ01)、中央高校专项基金(300102279209)
中文摘要:东准噶尔卡拉麦里地区巴塔玛依内山组为一套玄武岩-安山岩-英安岩-流纹岩组合,其时代归属及形成的构造背景争议已久。本文通过对双井子一带该组火山岩下部玄武岩开展LA-ICP-MS锆石U-Pb定年和岩石地球化学分析,获得一组锆石加权平均年龄为335.1±9.3Ma,时代为早石炭世。年代学成果综合分析表明,巴塔玛依内山组为连续发育于早-晚石炭世的穿时地层。玄武岩样品SiO2含量46.49%~52.19%,富碱(Na2O+K2O=4.07%~8.55%),高钾(K2O/Na2O=0.35~1.31)和高A12O3 (15.62%~17.97%),里特曼指数δ>3.3,斑晶和基质中含有碱性矿物,为典型的碱性玄武岩。样品具有轻重稀土分异明显(La/Yb)N=3.08~5.25,弱Eu异常(δEu=0.90~1.06),相对富集大离子亲石元素(LILE),亏损高场强元素(HFSE)等地球化学特征。结合相关判别图解研究表明,岩浆起源于受俯冲流体交代的亏损地幔源区,在深部岩浆房中发生了矿物结晶分异作用,并在上升侵位过程中遭受了一定程度的陆壳物质混染。碱性玄武岩兼具板内玄武岩、后碰撞和岛弧火山岩特征,结合区域地质资料分析,其形成与卡拉麦里洋盆闭合之后的板内岩浆活动有关,是俯冲碰撞造山期后伸展背景下的产物。表明早石炭世准噶尔地块东北缘已经进入由碰撞挤压到伸展拉张的构造转换期。
中文关键词:碱性玄武岩  年代学  地球化学  巴塔玛依内山组  卡拉麦里地区  东准噶尔
 
Petrogenesis and Tectonic Implications of Alkali Basalts in Kalamaili area, East Junggar, Xinjiang(NW China): Constraints from Petrology, Geochronology and Geochemistry
Author NameAffiliationAddress
Li hai School of Earth Science and Resources, Chang''an University 陕西省西安市雁塔区育才路126号,长安大学地球科学与资源学院
Li yongjun School of Earth Science and Resources, Chang'
'
an University 
Xu xueyi China Aero Geophysical Survey & Remote Sensing Center for Land and Resources 
Yang gaoxue School of Earth Science and Resources, Chang''an University 
Wang zuopeng School of Earth Science and Resources, Chang''an University 
Xu qian School of Earth Science and Resources, Chang''an University 
Wang longjiang School of Earth Science and Resources, Chang''an University 
Abstract:The Batamayineishan Formation from Kalamaili area of East Junggar is built up of a set of basalt-andesite-dacite-rhyolite. The age and tectonic background of its formation have been disputed for long. In this paper, base on field investigations and detailed petrologic and geochronologic researches of Batamayineishan Formation in Shuangjingzi area and LA-ICP-MS zircon U-Pb dating and petrological geochemical analysis of basalts from the lowermost of this formation were carried out. The results show that the formation age of basalts collected is 335.1±9.3Ma, which belong to Late Carlboniferous epoch. Combined with the previous chronological data and the results of this paper, it is suggests that the Batamayineishan Formation is a diachronic lithostratigraphic unit from Early Carboniferous to Late Carboniferous. Geochemically, basalts samples contains SiO2 of 46.49%~52.19%, they have relatively high Na2O+K2O (4.07%~8.55%), K2O/Na2O (0.35~1.31) and A12O3 (15.62%~17.97%). Their Rittman indices are greater than 3.3, and alkaline minerals are enriched in phenocryst and matrix, with the typical characteristics of alkaline basalt. The REE patterns of the alkaline basalts are characterized by strongly fractionated REE patterns (La/Yb)N=3.08~5.25 and without Eu anomalies. The concentrations of incompatible trace elements such as Rb, Ba, Sr are enriched, whereas the high field strength element (eg. Nb, Ta and Ti) contents are depleted. Combined with discrimination diagrams, the authors hold that basalts from the Batamayineishan Formation were derived from the partial melting of a depleted mantle that had been metasomatized by subduction-related fluids, possibly with a few additions of continental materia, then fractional crystallization of mafic-minerals and Fe-Ti oxides occurred during magmatic evolution. Alkaline basalts have the characters of intra-plate basalt, post-collision and arc volcanic rock. In combination with the regional geological background, alkaline basalts of Batamayineishan Formation are formed in post-collision extensional period after the closure of Karamaili Ocean. It shows that in Late Carlboniferous the northeastern Junggar terrane entered a key stage of structural transformation from collisional extrusion to extension.
keywords:Alkaline basalt  Geochemistry  Batamayineishan Formation  Kalamaili area  East Junggar
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