福建连江笔架山碱长花岗斑岩年代学、岩石地球化学特征的地质意义  

Chronology and Geochemical Characteristics of Bijiashan Alkali-feldspar Granite Porphyry in Lianjiang, Fujian Province, and their Geological Significance

作　　者：阙永泉 Que Yongquan(The Eighth Geologic Party of Fujian Province,Longyan,364000)

机构地区：[1]福建省第八地质大队,龙岩364200

出　　处：《福建地质》2022年第4期269-278,共10页Geology of Fujian

基　　金：福建省公益性基础性地质调查项目“福建1∶5万连江县黄岐镇幅区域地质调查”。

摘　　要：笔架山碱长花岗斑岩岩体位于连江县城东北侧笔架山一带,岩体中LA-ICP-MS锆石U-Pb同位素年龄为(95.4±0.62)Ma,属燕山运动晚期的产物。主量元素总体表现出富硅、碱,贫钙、镁、铁,高铁镁比、低固结指数和高分异指数的特征;微量元素中大离子亲石元素Th、U富集明显,而与斜长石分离结晶相关的高场强元素Ba、Sr则亏损明显;轻稀土富集,δEu为0.13~0.44,具明显的负铕异常,稀土配分模式图曲线形态为典型的“海鸥型”;岩石相对富铝,为高分异铝质A型花岗岩。岩体属于A2型花岗岩,形成于大陆边缘后造山伸展构造环境。笔架山岩墙的存在进一步证实了永定—闽江口断裂带晚白垩世时期对岩浆侵入有着强烈的控制作用。Bijiashan rock mass is distributed around Bijiashan Mountain, which located in northeast of the Lianjiang County.The main lithology is alkali feldspar granitic porphyry, The LA-ICP-MS Zircon U-Pb isotopic age of Bijiashan rock mass is(95.4±0.62)Ma, which belongs to the early Upper Cretaceous.The main elements are characterized by high contents of silicon and alkali and low contents of calcium, magnesium, iron, high ratio of iron-magnesium,high DI and low SI;Trace elements are characterized by enrich large ion lithophile elements Th and U,and the strong depletion of high field strength elements Ba and Sr,which related to the separation crystallization of plagioclase;The rare earth elements of Bijiashan rock mass is rich, the δEu values ranges from 0.13 to 0.44, the curve of rare earth element partition diagram like a seagull.Bijiashan rock mass is relatively rich in aluminum, It is a high differentiated aluminum A-type granite.The granites belong to A2 type granites, which means is formed in the post-collision extensional tectonic environment of continental margin.The existence of Bijiashan rock mass further confirms that the Yongding-Minjiangkou fault strongly controlled the magmatic intrusion during the early Upper Cretaceous.

关 键 词：碱长花岗斑岩 A型花岗岩 锆石U-PB同位素年龄 岩石地球化学 连江笔架山 

分 类 号：P588.12[天文地球—岩石学] P597.3[天文地球—地质学]