苏丹红海州新元古代A型花岗岩的地球化学特征及构造意义  

Geochemical characteristics and tectonic implications of the Neoproterozoic A-type granites in Red Sea State,Sudan

作　　者：周佐民 李勇[3] 刘晓阳 吴兴源 ZHOU Zuo-min;LI Yong;LIU Xiao-yang;WU Xing-yuan(Tianjin Center,China Geological Survey,Tianjin 300170,China;Mining institute of Southern Africa,China Geological Survey,Tianjin 300170,China;Wuhan Center,China Geological Survey,Wuhan 430205,China)

机构地区：[1]中国地质调查局天津地质调查中心,天津300170 [2]中国地质调查局南部非洲矿业研究所,天津300170 [3]中国地质调查局武汉地质调查中心,武汉430205

出　　处：《华北地质》2023年第1期71-79,86,共10页North China Geology

基　　金：中国地质调查局项目“中-苏合作苏丹红海州地区1/25万地质地球化学调查项目(1212011220911)”。

摘　　要：苏丹红海州位于努比亚地盾,本文在该地厘定出一套新元古代花岗岩,由中粗粒-中细粒正长花岗岩、中细粒碱长花岗岩组成,LA-ICP-MS定年结果显示,岩体形成于713±4Ma,属于泛非造山事件的产物。花岗岩SiO_(2)含量较高,为70.80%~77.83%,A/CNK为0.94~1.08,A/NK为1.12~1.44,为准铝质-弱过铝质花岗岩。花岗岩具有相似的稀土元素和微量元素配分模式,稀土配分模式呈右倾V字形曲线,轻重稀土分异中等(LREE/HREE=2.46~7.13),δEu为0.30~0.57,负铕异常中等-强烈。富含大离子亲石元素Th、U、K和高场强元素Zr、Hf,亏损高场强元素Nb、Ta、Sr、P和Ti。花岗岩具有低I_(Sr)比值、亏损ε_(Nd)(t)值和ε_(Hf)(t)值,T_(DM1)与T_(DM2)值较为一致。岩体为A_(2)型花岗岩,形成于俯冲阶段弧后拉张环境,因弧后伸展减薄导致软流圈物质上涌,明显的升温、减压促使新生地壳部分熔融。The Red Sea State of Sudan is located in the Nubian shield.A series of Neoproterozoic granites are identified in the Red Sea State,which consist of medium-coarse-and medium-fine-grained syenogranites and middle-fine-grained alkli feldspar granites.Zircon U-Pb dating implies the granites are intruded in 713±4 Ma,which are formed in Pan-African orogenic event.They show high SiO_(2) contents(70.80%~77.83%).They are metaluminous or weak peraluminous with A/CNK ratios of 0.94~1.08 and A/NK ratios of 1.12~1.44.They show the similar Chondrite-normalized REE and multi-trace elements patterns.The REE patterns are rightinclined with REE medium differentiations of LREE/HREE ratios of 2.46~7.13 and display“V”shaped curve and medium to strong Eu anomaly withδEu values of 0.30~0.57.The granites are characterized by the enrichment of large ion lithophile elements(LILEs)such as Th,U,K and high field-strength elements(HFSEs)such as Zr,Hf and by the depleted Nb,Ta,Sr,P and Ti contents.They show low I_(Sr) ratios,depletedε_(Nd)(t),ε_(Hf)(t)values and the similar T_(DM1) and T_(DM2) values.The granites chemically show A_(2)-type affinity.We propose that the 713 Ma A-type magmatism might be driven by upwelling of asthenosphere and subsequent partial melts of juvenile crust of Nubian shield on conditions of obvious Heating and decompression in a back-arc extensional setting.

关 键 词：苏丹红海州 努比亚地盾 新元古代 A型花岗岩 新生地壳 弧后拉张 

分 类 号：P588.121[天文地球—岩石学] P595[天文地球—地质学] P542