摘要
西昆仑-喀喇昆仑甜水海地体南部克勒青河组火山岩,与下三叠统克勒青河组(T3k)钙质页岩、灰岩互层,基性端元枕状玄武岩硅含量为SiO_(2)=47.68%~52.96%,呈富铝、高钙特征,即Al_(2)O_(3)=10.25%~11.28%, CaO=8.19%~9.23%,里特曼指数σ=3.38~6.08,属碱性岩类,且富集大离子亲石元素K、Rb、Ba、Th、LREE,具微弱Eu负异常,δEu均值为0.92;酸性端元英安岩具较高的Al、Na含量,即Al2O3=14.96%~16.10%,Na_(2)O=3.21%~3.85%,而Ti、 Mg及Ca含量较低,即TiO_(2)=0.53%~0.68%, MgO=2.32%~3.23%及CaO=2.36%~3.41%,富集大离子亲石元素Rb、Th、U、K,亏损高场强元素Ta、Nb、Ti,轻稀土略富集,重稀土略亏损,配分模式为右倾海鸥型,具弱Eu负异常,δEu均值为0.67。英安岩LA-ICP-MS锆石U-Pb年龄为210±0.49 Ma,表明其形成于晚三叠世,玄武岩与英安岩属同源,源区主要为地壳同化混染的产物,且具幔源特征。另通过区域岩浆活动对比研究,判断克勒青河组双峰式火山岩形成于晚三叠世的岛弧和板内伸展环境,并可能与古特提斯洋南向俯冲有关,俯冲导致板内拉张,总体为一套具板内地球化学效应,岛弧-弧后构造背景下局部伸展形成的“双峰式”火山岩。
The volcanic rocks of the Keleqinghe Formation are interbedded with calcareous shale and limestone of the Lower Triassic Keleqinghe Formation(T3k)in the south of Tianshui Haitian land block in West Kunlun‑Karakoram orogenic belt.The silicon content of basic end‑member pillow basalt is SiO_(2)=47.68%~52.96%,which is aluminum‑rich and high calcium,Al_(2)O_(3)=10.25%~11.28%,CaO=8.19%~9.23%,Rittman indexσ=3.37~6.08,belonging to alkaline rocks,and rich in large ion lithophile elements K,Rb,Ba,Th,LREE,with weak negative Eu anomaly.The average value of δEu is 0.92.The acidic end‑member dacite has high Al and Na contents,Al_(2)O_(3)=14.96%~16.1%,Na_(2)O=3.21%~3.85%,while Ti,Mg and Ca contents are low,TiO_(2)=0.53%~0.68%,MgO=2.32%~3.23% and CaO=2.36%~3.41%,with enriched large ion lithophile elements Rb,Th,U,K,and depleted high field strength elements Ta,Nb,Ti.The light rare earths are slightly enriched and heavy rare earths are slightly depleted.The distribution pattern is right‑leaning seagull type with weak negative Eu anomaly.The average value of δEu is 0.65.The LA‑ICP‑MS zircon U‑Pb age of dacite is 210±0.49 Ma,indicating that it was formed in the Late Triassic period.The basalt and dacite are homologous,and the source area is mainly the product of crustal assimilation and contamination,with mantle‑derived characteristics.In addition,through the comparative studies of regional magmatic activities,the rustles indicate that the bimodal volcanic rocks of the Keleqinghe Formation were formed in the island arc and intraplate extension environment of the Late Triassic,and may be related to the southward subduction of the Tethys Ocean,which led to the intraplate tension.Generally,it can be concluded as a set of“bimodal”volcanic rocks with intraplate geochemical domino effect and local extension under the background of island arc‑arc back structure.
作者
任文林
张博文
苏春媚
孙亚飞
王琦玮
Ren Wenlin;Zhang Bowen;Su Chunmei;Zhang Yafei;Wang Qiwei(College of Geology and Mining Engineering Xinjiang University,Urumqi 830049;Laboratory of Continental Dynamics and Metallogenic Prognosis of Central Asian Orogenic Belt,Xinjiang University,Urumqi 830049)
出处
《地质科学》
CAS
CSCD
北大核心
2023年第3期864-889,共26页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
新疆维吾尔自治区自然科学基金项目(编号:2021D01C042)资助。
