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J4 ›› 2016, Vol. 22 ›› Issue (1): 113-.DOI: 10.16108/j.issn1006-7493.

• 构造岩石地球化学 • 上一篇    下一篇

青海刚察泉吉地区中酸性侵入岩年代学特征及其意义

张国栋,徐争启,龚骏,奉军,韩亚彪,张建旺,周洋,黄泽森   

  • 出版日期:2016-03-20 发布日期:2016-04-14

Geochronology and Significance of Intermediate-acid Intrusive Rocks in Quanji Area, Gangcha, Qinghai

ZHANG Guodong, XU Zhengqi, GONG Jun, FENG Jun, HAN Yabiao, ZHANG Jianwang,ZHOU Yang, HUANG Zesen, ZENG Xuefeng, ZHANG Kaiju, WANG Jiankang, CHENG Jian   

  • Online:2016-03-20 Published:2016-04-14

摘要:

青海刚察泉吉地区中酸性侵入岩发育,为了进一步查明侵入岩的特征、侵入时代和形成环境,对其进行了地质学、
岩石地球化学及年代学研究。LA-ICP-MS锆石U-Pb定年结果表明,研究区中酸性侵入岩侵位年龄主要集中在430~455 Ma,指
示岩体为晚奥陶世—早志留世,指示两个期次岩浆产物,侵位于巴龙贡噶尔组的花岗闪长岩测年结果显示锆石206Pb/238U值
为444±11 Ma,指示该花岗闪长岩体的侵位时代属晚奥陶世,因此限定了巴龙贡噶尔组(Sb) 时代上限应该早于晚奥陶
世。从岩石地球化学特征来看,花岗岩类表现为富钾、准铝—过铝质,富集大离子亲石元素Rb、K 和Ba,亏损高场强元素
Nb、Ti和P,具弱铕负异常;闪长岩类表现为富钾、准铝质、铕负异常特征不明显。从形成环境来看,研究区中酸性侵入
岩均具有大陆碰撞环境的特征。结合区域地质构造环境及前人研究成果,研究区侵入岩是俯冲—碰撞环境下晚奥陶世-早
志留世的加里东期产物。

关键词: 中酸性侵入岩, LA-ICP-MS锆石U-Pb定年, 地球化学, 年代学, 泉吉

Abstract:

There are many intermediate-acid intrusive rocks in Quanji area. In order to better understand of the characteristics,
intrusion age, and formation environment, we have studied the geology, geochemistry, and geochronology of intermediate-acid intrusive
rocks in Quanji area. LA-ICP-MS zircon U-Pb results show that the intrusion age of granitoid rocks is 430~455 Ma, indicating that
magmatic intrusion took place in different phases during Late Ordovician to Early Silurian in the study area. U-Pb age data show that
the granodiorite was formed at 444±11 Ma, i.e., late Ordovician. Thus, the Balonggonggaer Formation should be earlier than the Late
Ordovician. Geochemical characteristics show that granitoid is rich in K and excessive in Al, enriched in LILE(Rb, K and Ba) ,
depleted in HFSE (Nb,Ti and P) with a weak negative europium anomaly. Diorites are rich in K, and quasi-aluminous and have a
negative europium anomaly that is not obvious. Granite and granodiorite have a weak europium negative anomaly. Quartz diorite is not

obvious. Intermediate-acid intrusive rocks have characteristics of continental collision in terms of formation environment. Based on
regional tectonic setting and previous research results, we infer that intermediate-acid intrusive rocks were produced in a subduction or
collision setting during the Caledonian orogeny from Late Ordovician to Early Silurian.

Key words: intermediate-acid intrusive rocks, LA-ICP-MS ziron U-Pb dating, geochemistry, geochronology, Quanji