东昆仑东段瓦勒尕矿区基性岩脉地球化学特征及地质意义  

GEOCHEMICAL CHARACTERISTICS AND GEOLOGICAL IMPLICATION OF MAFIC DIKES FROM THE WALEGA MINING AREA IN THE EASTERN SEGMENTOFTHEEASTKUNLUNOROGENICBELT

作　　者：张方然 丁枫[1,2] 黄勇[3] 范宇航[1] 李文韬[1] 孙培均 郭香敏 ZHANG Fangran;DING Feng;HUANG Yong;FAN Yuhang;LI Wentao;SUN Peijun;GUO Xiangmin(College of Earth and Planetary Sciences,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Key Laboratory of Tectonic Mineralization and Accumulation,Natural Resources Department,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Civil-Military Integration Center of China Geological Survey,Chengdu,Sichuan 610036,China)

机构地区：[1]成都理工大学地球与行星科学学院,四川成都610059 [2]成都理工大学自然资源部构造成矿成藏重点实验室,四川成都610059 [3]中国地质调查局军民融合地质调查中心,四川成都610036

出　　处：《矿物岩石》2024年第2期47-61,共15页Mineralogy and Petrology

基　　金：国家自然科学基金面上项目(批准号:42377194);四川省自然科学基金面上项目(编号:2023NSFSC0282);四川省中央引导地方科技发展项目(编号:2023ZYD0151)。

摘　　要：东昆仑造山带是青藏高原东北缘的一条巨型构造岩浆岩带,其上极少发生新生代岩浆活动。本次研究对东昆仑东段瓦勒尕矿区新生代基性岩脉开展了岩相学、岩石地球化学及年代学特征等方面的研究。基性岩脉呈近EW向展布,与区域断裂延伸方向较为一致。基性岩脉主要岩石类型为辉长岩和辉绿岩,岩石地球化学显示具有低-中钾钙碱性准铝质的特征(A/CNK值为0.70~0.79,AR值为1.26~1.35,σ值为1.26~1.35),大离子亲石元素富集(Ba, K,Rb),而相对亏损高场强元素(Nb, Ta),轻重稀土分馏不明显(LREE/HREE平均值分别为2.92和2.26),无铕异常(δEu特征值分别为0.97~1.05),微弱的正铈异常(δCe特征值分别为1.03~1.07),其分布模式呈近平坦的曲线。所有锆石稀土元素表现出典型的岩浆锆石特征,具有Ce正异常和Eu负异常,轻稀土亏损且重稀土富集的陡倾斜模式。LA-MC-ICPMS锆石U-Pb定年结果显示瓦勒尕基性岩脉形成时代为中新世早期(17.31±0.26 Ma和16.93±0.33 Ma),岩石地球化学显示具其有与拉张环境相关的板内玄武岩特征,基性岩脉同藏北新生代火山岩具有相似的构造背景。结合区域构造环境,推测东昆仑走滑断裂的活动引起下部岩石圈富集地幔发生减薄熔融作用,富集地幔上涌,熔体沿着东昆仑地区深大断裂向上运移,并遭受下地壳物质的混染作用,最终于瓦勒尕地区侵位结晶而形成。这些基性岩脉填补了东昆仑造山带新生代岩浆活动的空缺。The East Kunlun orogenic belt,located on the northeastern margin of the Tibetan Plateau,is a significant tectonic magmatic belt.However,Cenozoic magmatic activity is rare in this region.This paper examines the lithography,petrogeochemistry,and chronology of the basic dikes in the Valega mining are-a,situated in the eastern part of East Kunlun.The basic dikes in the study area are predominantly orien-ted in an east-west direction,aligning with the regional fault trends.The main rock types identified in these dikes are gabbro and diabase.Geochemical analysis of the rocks reveals characteristics of low to me-dium potassium-calc alkaline quasi-aluminum composition,with A/CNK values ranging from O.70 to 0.79,AR values from 1.26 to 1.35,and o values also from 1.26 to 1.35.The rocks are enriched in large ion lithophile elements(Ba,K,Rb)and relatively depleted in high field strength elements(Nb,Ta).The fractionation between light and heavy rare earth elements(REE)is minimal,with average LREE/HREE ratios of 2.92 and 2.26.The δEu values show no significant anomalies(ranging from 0.97 to 1.05),while δCe values indicate a slight positive anomaly(ranging from 1.03 to 1.07).The rare earth element compo-sition of zircons from the mafic dikes exhibits typical magmatic zircon characteristics,including a positive Ce anomaly,a negative Eu anomaly,a deficit in light REE,and enrichment in heavy REE.LA-MC-ICPMS zircon U-Pb dating results indicate that the Valga basic dikes formed in the early Miocene,with a-ges constrained to 17.31±0.26 Ma and 16.93±0.33 Ma.The geochemical characteristics suggest that the basic dikes are related to intraplate basalt formed in a tensile environment,similar to the tectonic back-ground of Cenozoic volcanic rocks in northern Tibet.From a regional tectonic perspective,it is proposed that activities along the East Kunlun strike-slip fault induced thinning and melting of the lower lithospheric enriched mantle,leading to the upwelling of this enriched mantle.The ascending melt magma migrated a-long deep f

关 键 词：基性岩脉 岩石地球化学 构造环境 瓦勒尕矿区 东昆仑 

分 类 号：P581[天文地球—岩石学] P595[天文地球—地质学]