福建沿海晚中生代花岗质岩石成因及其地质意义  

Petrogenesis of the Late Mesozoic granitic rocks in southeast coastal areas of Fujian Province and its geological significance

作　　者：李良林[1,2,3] 周汉文[2] 陈植华[4] 王锦荣[5] 陈正华[1,3] 陈威[1,3] 

机构地区：[1]外生成矿与矿山环境重庆市重点实验室/重庆地质矿产研究院,重庆400042 [2]中国地质大学(武汉)地球科学学院,湖北武汉430074 [3]煤炭资源与安全开采国家重点实验室重庆研究中心.重庆400042 [4]中国地质大学(武汉)环境学院,湖北武汉430074 [5]中国冶金地质勘查总局第二地质勘查院,福建莆田351111

出　　处：《地质通报》2013年第7期1047-1062,共16页Geological Bulletin of China

基　　金：福建国土资源厅项目(编号:2009046095)

摘　　要：福建白云山、鼓山和石牛山均位于福建沿海地带,该区域花岗岩类分布广泛。LA-ICP-MS锆石U-Pb定年结果显示,白云山、鼓山(魁歧)和石牛山地区花岗岩年龄分别为99.3Ma±1.8Ma、99.4Ma±2.3Ma和94.7Ma±1.4Ma,属晚白垩世早期的产物。花岗岩均具有富硅、富碱、贫钙镁、高分异指数等特点,属弱过铝到准铝质岩石。稀土元素具中-强Eu负异常,总体呈现轻稀土元素富集的右倾"V型"模式。微量元素Rb、U、Th、La等强烈富集,相对亏损Ba、Sr、P、Ti等元素。岩相学和地球化学特征分析表明,研究区花岗岩属典型的A型花岗岩,其中魁歧花岗岩为碱性A型花岗岩,其余地区为铝质A型花岗岩。研究表明,研究区A型花岗岩具有相似的源区组成;岩浆来源于地壳物质的部分熔融,并可能有部分地幔物质参与;碱性A型花岗岩较铝质A型花岗岩可能有更多的地幔物质加入。结合地球化学、野外地质、区域背景及年龄资料综合判定,中国东南沿海2类A型花岗岩为古太平洋板块俯冲体系中弧后伸展环境下的产物。Baiyunshan, Gushan and Shiniushan are all located in coastal areas of Fujian Province, and granitoids are widely distributed in these areas. LA-ICP-MS zircon U-Pb dating shows that the petrogenetic ages of Baiyunshan, Gushan （Kuiqi） and Shiniushan are respectively 99.3Ma±1.8Ma, 99.4Ma＋2.3Ma and 94.7Ma±1.4Ma, suggesting that the granites were formed in the early Late Creta- ceous period. The granites are characterized by rich silicon and alkali, poor calcium and magnesium, and high fractionation indexes, thus belonging to metaluminous to weakly peraluminous granites, tLEE are characterized by intermediate to strong negative Eu anomalies and exhibit right-oblique ＂V＂ patterns with LREE enrichment. Trace elements show that granites are strongly enriched in Rb, U, Th and La while relatively depleted in Ba, Sr, P and Ti. The petrom＇at^hic and geochemical characteristics indicate that thegranites belong to typical A-type granitoids, in which Kuiqi granites belong to alkaline A-type granites whereas the other rock bodies belong to aluminous A-type granites. Studies have shown that the two kinds of A-type granites may have similar sources; magma o- riginated from the partial melting of crustal material, with the probably addition of some mantle material; however, alkaline A-type granites might have had more added mantle material than the aluminous A-type granites. In combination with geochemistry, field ge- ology, regional background and geochronology, it is suggested that the two kinds of A-type granites in southeast coastal areas of China should be the products of back-arc extension background in the Paleo-Pacific plate subduction system.

关 键 词：碱性A型花岗岩 铝质A型花岗岩 晚中生代 古太平洋板块俯冲 福建沿海 

分 类 号：P534.5[天文地球—古生物学与地层学] P581[天文地球—地质学]