摘要
巴音沟蛇绿岩侵位于辉长岩中的斜长花岗岩亏损LREE和不相容元素，（Ce／Yb）N=0．67—0．88，（Gd／Yb）N=0．63—0．73，εNd（t）=8．36—8．52，^87Sr／^86Sr（t）=0．70365～0．70408，为亏损地幔来源花岗岩，是蛇绿岩的组成部分。斜长花岗岩的精细SHRIMP锆石U—Pb年龄为324．8±7．1Ma，表明巴音沟蛇绿岩形成于早石炭世晚期。巴音沟蛇绿岩中辉长岩、辉绿岩、基性熔岩REE球粒陨石标准化和微量元素原始地幔标准化分配型式呈平坦型分布，（Ce／Yb）N=0．63～1．36，（Gd／Yb）N=1．02—1．41，近似于N—MORB分配型式.^87Sr／^86Sr比值变化于0．70306—0．70439，εNd（t）=4．63～8．69，表明其岩浆主体来源于N—MORB，但在形成过程中有OIB组分的加入。结合天山石炭纪区域火山岩的研究，认为巴音沟蛇绿岩形成于大陆裂谷向大洋裂谷转化的构造环境，它是天山造山带晚古生代“红海型”洋盆的地质记录．
The plagiogranites intruding as veins in gabbros in Bayingou ophiolite fragment are depleted in LREE and incompatible elements with （Ce/Yb） N = 0.67 - 0.88, （Gd/Yb） N = 0.63 - 0.73, εNd （t） = 9. 20 - 9. 35, ^87Sr/^86 Sr （t） = 0. 70365 - 0. 70408, indicating they are derived from depleted mantle source and is a part of the ophiolite. The representative samples of plagiogranites yield the SHRIMP zircon U-Pb age of 324.8 ± 7.1Ma, which is consistent with the formation age of the ophiolite and showing the Bayingou ophiolite occurred in late stage of Early Carboniferous. The gabbros, diabases and basic volcanic rocks in Bayingou ophiolite fragment show flat patterns in chondrite-normalized REE diagram and primitive mantle-normalized trace elements diagram with （Ce/Yb） N = 0.63 - 1.36, （Gd/Yb）N = 1.02 - 1. 41 and are characterized by the ^87Sr/^86 Sr = 0. 70306 - 0. 70439, εNd （t） = 4.63 - 8.37, suggesting the basic magma of the ophiolite mainly originated from N-MORB source but mixed with OIB source during the processes of magma formation. Combining with the study of Carboniferous regional volcanic rocks and the geochronological and geochemical data from the Bayingou ophiolite fragment, can provide us an insight into the understanding of the tectonic setting of the ophiolite： The Bayingou ophiolite occurred in a transition tectonic setting from continental riftism to ocean riftism, which is the geological record of an Early Carboniferous ＂Red Sea type＂ ocean basin.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2006年第1期83-94,共12页
Acta Petrologica Sinica
基金
国土资源大调查项目(编号:200313000063
200313000028)
国家自然科学基金项目(编号:40472044)
科技部"973"项目(编号:2001CB409801)联合资助.
作者简介
徐学义，男，1966年生，研究员，博士，主要从事区域岩石学及地球化学研究．E-mail：xaxxueyi@cgs．gov．cn。
