摘要
为了解甘肃北山黑山头石英二长闪长岩体侵位时代、岩石成因,进一步探讨北山造山带晚古生代构造演化,对该岩体开展了年代学和岩石地球化学研究。结果显示,黑山头石英二长闪长岩的LA-ICP-MS锆石U-Pb加权平均年龄为(267.7±1.3)Ma,为中二叠世。地球化学数据表明,岩体为高钾钙碱性、准铝质系列,SiO2含量为57.32%~64.00%,全碱(K2O+Na2O)平均含量为6.10%,K2O/Na2O为0.83~1.34,Al2O3含量为15.08%~16.32%。稀土元素球粒陨石标准化曲线明显右倾,轻稀土相对富集(LREE/HREE为7.05~7.61),δEu为0.70~0.85,具弱Eu负异常。微量元素相对富集大离子亲石元素Rb和强不相容元素Th、U及高场强元素Zr、Hf,显著亏损高场强元素Ba、Nb、Ti、P。结合区域地质背景,认为北山南部地区在中二叠世已完成洋-陆构造转化,进入后碰撞板内裂谷演化阶段,黑山头石英二长闪长岩是在该背景下岩浆作用的产物。
The chronological and geochemical chracteristics of the Heishantou quartz monzodiorite in the Beishan area, Gansu Province have been studied in order to clarify its emplacement age and petrogenesis, and to further discuss the Late Paleozoic tectonic evolution of the Beishan orogenic belt. The results show that the Heishantou quartz monzodiorite has the LA-ICP-MS zircon U-Pb weighted average age of(267.7±1.3) Ma, indicating that it was formed in Middle Permian. Geochemical data show that this intusion belongs to a high-K calc-alkaline meta-aluminous series, with SiO2contents of 57.32%~64.00%, average total alkalinity(K2O+Na2O) content of 6.10%, K2O/Na2O ratios of 0.83~1.34, and Al2O3contents of 15.08%~16.32%. The chondrite-normalized REE patterns are evidently right-declined, with relatively enriched LREE(LREE/HREE=7.05~7.61) and slight Eu negative anomalies(δEu=0.70~0.85). samples of this intrusion are relatively enriched in Rb of the large ion lithophile elements, Th and U of the strong incompatible elements, and Zr and Hf of the high field strength elements, but obviously depleted in Ba, Nb, Ti and P of the high field strength elements. Combined with the regional geological background, it is believed that the southern Beishan had already completed the ocean-to-continent tectonic transformation and had entered the stage of post-collision intraplate rift evolution in the Middle Permian and the Heishantou quartz monzodiorite was a product of magmatism under such tectonic background.
作者
杨镇熙
赵青虎
张晶
陈世明
张立涛
李省晔
荆德龙
龚振中
赵吉昌
YANG Zhen-xi;ZHAO Qing-hu;ZHANG Jing;CHEN Shi-ming;ZHANG Li-tao;LI Sheng-ye;JING De-long;GONG Zhen-zhong;ZHAO Ji-chang(Fourth Institute of Geological and Mineral Exploration of Gansu Bureau of Geology and Mineral Resources,Jiuquan,Gansu 735000,China;Xi'an Center of Geological Survey,China Geological Survey,Xi'an 710054,China)
出处
《矿物岩石地球化学通报》
CAS
CSCD
北大核心
2022年第6期1165-1177,共13页
Bulletin of Mineralogy, Petrology and Geochemistry
基金
甘肃省基础地质调查项目(甘财经二[2017]105号,[2018]59号,[2019]39号
甘资财环[2020]28号)
陕西省自然科学基础研究计划项目(2019JQ-934)。
