皖南印支期石英斑岩的首次发现及其构造意义  

The first discovery of Indosinian quartz porphyry in Dongkengkou Village, southern Anhui Province

作　　者：刘秀[1] 余心起[1] 李鹏举[1,2] 陈子微 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]四川理工学院经济与管理学院,四川自贡643000

出　　处：《地质通报》2016年第6期1015-1024,共10页Geological Bulletin of China

基　　金：国家自然科学基金项目(批准号:41272232)

摘　　要：印支时期,中国东南部地区构造运动活跃,岩浆活动较为发育。但是,皖南地区一直未发现该时期侵入岩。近期在安徽省黄山市徽州区东坑口村北约500m处x046县道旁,发现石英斑岩脉体。用LA-ICP-MS技术测得其中锆石的U-Pb年龄为245.2±2.4Ma,此年龄代表石英斑岩的结晶年龄,即形成于印支期中三叠世,而非前人一直认为的燕山期岩浆活动产物。岩石地球化学特征显示,东坑口石英斑岩富集Th、La、Ce等大离子亲石元素及轻稀土元素,亏损Ba、Sr、P、Ti等高场强元素,具有高的10000×Ga/Al值及Zr、Nb、Ce、Y含量,岩石中可见半自形的石英和斜长石,具有A型花岗岩的特征。皖南印支期A型花岗岩的发现,为区域构造-岩浆演化研究提供了新的科学依据,对理解和构建中国东南部乃至华南地区早中生代构造演化具有重要意义。It is generally thought that both tectonic events and magmatic activities during the Indosinian period were intense in southeastern China. In contrast, the Indosinian magmatic activities in southern Anhui area were generally not considered to be existent, because there was not any previous reported Indosinian intrusive rock in this area. In this paper, the authors obtained LA-ICP-MS zircon U-Pb weighted average age of 245.2±2.4Ma for the quartz porphyry dyke from the side of x046 highway, about 500m north of Dongkengkou Village, Huizhou District, Huangshan City, southern Anhui Province, which implys that the Dongkengkou quartz porphyry （DQP） was formed during Indosinian period rather than in Yanshanian period. The bulk-rock chemical data indicate that the DQP is enriched with LILE, LREE and depleted in high field-strength elements Ba, Sr, P, Ti, and possesses high 10000×Ga/Al ratios and high Zr, Nb, Ce and Y values. Petrologically, the DQP has hypidiomorphic quartz and plagioclase, exhibiting A-type granite characteristics. The confirmation of the Indosinian A-type granite from southern Anhui area provides new scientific evidence for understanding the regional tectono-magmatism history, and finally supplies extra evidence for remodeling the tectonic and geodynamic evolution of southeast China.

关 键 词：LA-ICP-MS锆石U-PB年龄 印支期 东坑口 石英斑岩 皖南 

分 类 号：P588.132[天文地球—岩石学]