摘要
满洲里南部玛尼吐组火山岩的岩相学鉴定为安山岩、粗安岩和粗面岩,化学成分显示其以粗面岩为主,少量流纹岩。LA-ICPMS锆石U-Pb定年结果显示其形成于146～158Ma之间的晚侏罗世。火山岩富碱高钾,属碱性系列;稀土总量较高(∑REE=328.2×10-6～419.2×10-6),轻重稀土分馏较明显((La/Yb)N=12.87～23.10),中等负铕异常(δEu=0.41～0.70);富集大离子亲石元素Rb、K和轻稀土元素,亏损高场强元素Nb、Ta、P、Ti。具有高Rb/Sr比值(0.34～1.88)和正的εHf(t)值(3.68～8.65),锆石176Hf/177Hf介于0.282780～0.282922之间,两阶段Hf模式年龄为652～972Ma的新元古代。岩浆源区物质为新元古代增生的基性火成岩地壳,火山岩形成于蒙古-鄂霍茨克洋闭合造山后的岩石圈伸展构造环境。
Petrographically,the volcanic rocks in Manitu Formation from southern Manchuria are composed of andesite,trachy-andesite and trachyte,but they are mainly trachyte with minor rhyolite based on chemical composition.Zircon U-Pb dating results show that they formed at Late Jurassic from 146 to 158Ma.These volcanic rocks are alkaline series in composition and rich in alkali and potassium;they are high in total rare earth elements（∑REE=328.2×10-6~419.2×10-6）,highly fractionated LREE from HREE（（La/Yb）N=12.87~23.10） and moderately negative Eu anomalies（δEu=0.41~0.70）.They contain high LILE（e.g.,Rb and K） and LREE,high ratios of Rb/Sr（0.34~1.88） and positive values of εHf（t）（3.68~8.65）,but low HFSE（e.g.,Nb,Ta,P and Ti）.The initial 176Hf/177Hf ratios for magmatic zircons from these volcanic rocks vary in the range of 0.282780~0.282922,and the two-stage model ages of 652~972Ma.The data suggest that the magmas for these volcanic rocks derived from the newly accreted Neoproterozoic basic igneous crusts,and formed during the extensional setting of lithosphere after the closure of Mongol-Okhotsk Ocean.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2011年第10期3083-3094,共12页
Acta Petrologica Sinica
基金
中国核工业地质局项目(200805)
国家自然科学基金项目(41172058)
中国地质调查局项目(121201112108)
国家重点基础研究发展计划"973"项目(2009CB19303)
西北大学大陆动力学国家重点实验室开放课题基金联合资助
关键词
锆石年龄
地球化学
岩浆源区
玛尼吐组
满洲里南部
Zircon U-Pb dating
Geochemistry
Source of magma
Manitu Formation
Southern Manchuria
