第30卷第1期 2016年2月
现代地质 GEOSCIENCE
Vol. 30No.1 Feb.2016
西藏改则热那错地区下一中保罗统色哇组玄武岩
地球化学特征及其构造意义
翟玉良，王根厚，李典
（中国地质大学（北京）地球科学与资源学院，北京100083）
摘要：西藏改则热那错地区下一中侏罗统色哇组中含粗面玄武岩，元素含量测试表明，其Si0，含量为45.62%~ 48.46%，Al,0,含量为14.09%~16.51%；Na,0与K,0含量分别为2.68%~4.12%、1.35%~4.73%，K,0/Na,0= 0.34~1.77。岩石富集轻稀土元素、亏损重稀土元素，有弱的销正异常；总体富集Rb、Ba、U等元素，亏损Sr、Yb、 Th、Y等元素。地球化学特征表明其形成于大洋板内洋岛环境，岩浆来源于富集地慢，未受或很少受到地壳物质和陆下岩石圈的混染。玄武岩、玄武质砾石、灰岩构成了洋岛型岩石组合，结合色哇组为海底扇沉积环境的观点，可以推断班公湖一怒江洋盆在早一中侏罗世发育成熟洋壳。
关键词：热那错地区；色哇组；火山岩；地球化学；构造意义
中图分类号：P588.14
文献标志码：A
文章编号：10008527(2016)01007809
GeochemicalCharacteristicsandTectonicImplicationofBasaltinLower-Middle
JurassicSewaFormationinRenacuoAreaofGaize.Tibet.China
CUI Yu-liang, WANG Gen-hou, LI Dian
( School of Earth Sciences and Resources, China Unirersity of Geosciences, Bejing 100083, China)
Abstract : The trachy basalt was discovered in Lower-Middle Jurassic Sewa Formation in Renacuo area of Gaize , Tibet.The contents of Si0z,Al,03,Na,0 and K,0 are 45.62%-48.46%,14.09%-16.51%,2.68%-4.12% , 1.35% -4.73%, respectively, and the ratio of K,0 to Naz0 (K,0/Na,0) is 0.34 -1.77. The rocks are rich in LREE, and poor in HREE with a weak positive Eu anomaly, as well as an enrichment of ele-ments such as Rb, Ba, U and a depletion of elements like Sr, Yb, Th, Y as a whole. The geochemical charac teristics indicate that they are generated in oceanic island environment within the oceanic slab, and that the magma is derived from enriched mantle without or with a little contamination of crust materials and sub-continen tal lithosphere. The oceanic island rock combination consists of basalt, basaltic gravel and limestone. Combined with the idea that Sewa Formation is seafloor fan sedimentary environment, it can be inferred that the Bangong cuo-Nujiang ocean was mature oceanic crust in Early-Middle Jurassic.
Key words: Renacuo area; Sewa Formation; volcanic rock; geochemistry; tectonic implication
0引言　
怒江谷地延向国外，全长超过2800kml1-2]，是青藏高原一条重要的构造界线。前人！-5]已对洋盆
班公湖一怒江板块缝合带西起班公湖，东经性质、演化时限等进行了研究，初步认为班公湖改则、东巧，转东南经洛隆、八宿，继而沿滇西一怒江缝合带扩张洋壳形成于晚三叠世一早侏罗
收稿日期：2015-01-12；改回日期：2015-06-28；责任编辑：威开静。
基金项目：中国地质调查局区域地质调查项目（12120110860621212011221115）。
作者简介：崔玉良，男，硕士研究生，1989年出生，构造地质学专业，主要从事构造地质学研究。Email：814399394@qq.com 通信作者：王根厚，男，敦教授，博士生导师，1963年出生，构造地质学专业，长期从事构造地质学的教学与科研工作。
Email:wghcugh edu. cn。