赣南地区石雷石英闪长岩的成因:岩石化学、副矿物微量元素、锆石U-Pb年代学与Sr-Nd-Hf同位素制约  

Petrogenesis of Shilei quartz diorite in southern Jiangxi:Constraints from petrochemistry,trace elements of accessory minerals,zircon U-Pb dating,and Sr-Nd-Hf isotopes

作　　者：李光来 华仁民[1] 胡东泉[1] 黄小娥 张文兰[1] 王旭东[1] 

机构地区：[1]南京大学内生金属矿床成矿机制研究国家重点实验室,南京210093 [2]江西有色地质勘查局,南昌330001

出　　处：《岩石学报》2010年第3期903-918,共16页Acta Petrologica Sinica

基　　金：国家重点基础研究发展计划项目(2007CB411404);国家自然科学基金项目(40572057)资助

摘　　要：石雷石英闪长岩是赣南崇-余-犹地区比较特殊的闪长质侵入体。锆石的原位U-Pb定年表明,该岩体侵位于433.5±3.4Ma。全岩主量元素特征上显示出中偏酸性(SiO2=56.92%～64.70%),富Al(Al2O3=14.10%～14.83%),富碱(Alk=6.41%～7.40%)特别是富钾(K2O=3.86%～4.85%),镁、铁含量较高,MgO:3.47%～5.95%,FeOT:5.23%～8.14%以及低磷(P2O5=0.27%～0.4%)的特点;微量元素上主要富集K、Rb、Cs等大离子亲石元素和轻稀土元素,亏损Nb、Ta、Ti、P等高场强元素。磷灰石微量元素特征上显示高度富集稀土元素特别是轻稀土元素的特征;具有Eu的负异常(δEu=0.37～0.45)。ISr位于0.7073～0.7132之间,εNd(t)变化于-8.41～-4.97之间,两阶段钕模式年龄介于1.58～1.86Ga之间,Hf同位素组成相对均一,εHf(t)主要集中变化于-8～-2之间,两阶段Hf模式年龄加权平均为1.77±0.09Ga,这些特征都暗示了该石英闪长质岩体的形成是强烈壳幔相互作用的产物,区内加里东晚期可能发生了局部的岩石圈的减薄。Shilei quartz diorite is one of the most special diorites in Chongyi-Shangyou-Dayu area,southern Jiangxi. Zircon U-Pb dating for one quartz diorite yields an emplacement age of 433.5±3.4 Ma. Four samples are with middle contents of silica (SiO2:56.92%~64.70%),high contents of AL2O3 (14.10%~14.83%),Alk (6.41%~7.40%),K2O (3.86%~4.85%),MgO (3.47%~5.95%) and FeO (5.23%~8.14%) and low contents of P2O5 (0.27%~0.4%). They contain high contents of large ion lithophile elements such as K,Rb,Cs and light rare elements and low contents of high field strong elements such as Nb,Ta,Ti,P. Apatites are enriched in rare elements,their light rare elements contents are much higher than heavy rare elements contents. They have a low δEu (0.37~0.45). The Sr-Nd isotope compositions are characterized by the follows:Distinctively middle initial Sr isotopic ratios (ISr=0.7073~0.7132); low initial Nd isotopic ratios (εNd(t)=-4.97^-8.41),two-stage model age ranging from 1.58Ga to 1.86Ga; zircon Hf isotopic analysis yields main εHf(t) values of-8 to-2,with two-stage model age 1.77±0.09Ga. These characters indicate that Shilei quartz-diorite is the product of an intensive interaction between crust and mantle. The lithosphere of this area perhaps once thinned in Late-Caledonian.

关 键 词：石英闪长岩 地球化学 锆石U-PB定年 岩石成因 赣南石雷 

分 类 号：P588.122[天文地球—岩石学]