摘要
下泥盆统托让格库都克组高铝玄武岩产自东准噶尔青河地区野马滩一带。高铝玄武岩富含大量斜长石斑晶,属亚碱性系列。它们具有显著高A12O3(质量分数为17.22%～21.31%),低SiO2(47.12%～49.45%),高TFe2O3(8.50%～11.98%)、MgO(2.64%～5.63%)、Ni((5.75～27.87)×10^(-6))、Cr((0.99～25.62)×10^(-6)),以及高Sm/Yb值(1.13～1.96)、U/Th值(0.42～0.81)的特征,相对富集大离子亲石元素和亏损高场强元素,显示出典型的高铝玄武岩地球化学特征。进一步研究表明,其岩浆来源于受俯冲带流体交代地幔楔的部分熔融。此外,高Sr/Y值(43.16～47.07)和低Y(质量分数为(15.69～19.09)×10^(-6))、Yb((1.64～2.13)×10^(-6))显示玄武质岩浆源区有俯冲带洋壳物质的加入。高Al特征很可能与高压条件下斜长石的滞后结晶有关。地球化学特征表明,高铝玄武岩形成于岛弧环境。东准噶尔早泥盆世高铝玄武岩的发现丰富了本区火山岩岩类信息资料,并为构造演化研究提供了重要依据。
The high-alumina basalts of Lower Devonian Tuoranggekuduke Formation occur in Yematan of Qinghe area,East Junggar,China.The high-alumina basalts are rich in a large number of plagioclase phenocrysts,belonging to a sub-alkaline series.The basalts have significantly high A1 2O 3(the mass fraction is 17.22%-21.31%),low SiO 2(47.12%-49.45%),and high TFe 2O 3(8.50%-11.98%),MgO(2.64%-5.63%),Ni((5.75-27.87)×10^-6),Cr((0.99-25.62)×10^-6),and high Sm/Yb ratio(1.13-1.96),U/Th ratio(0.42-0.81),and they relatively enrich in large ion lithophile elements and deplete in high field strength elements,indicating the characteristics of the typical geochemical features of high-alumina basalts.The further research shows that the magma is derived from the partial melting of the mantle wedge modified by the subduction zone fluid.In addition,the basalts with high Sr/Y ratio(43.16-47.07),low Y(the mass fraction is(15.69-19.09)×10^-6)and Yb((1.64-2.13)×10^-6)indicate that the source of basaltic magma may contain subduction zone oceanic crust materials.The characteristics of high Al are likely to be related to the delayed crystallization of plagioclase under high pressure conditions.Geochemical characteristics indicate that these high-alumina basalts are formed in an island arc environment.The discovery of Early Devonian high-alumina basalts enriches the petrographic data of volcanic rocks in East Junggar and provides an important basis for the study of tectonic evolution.
作者
李永军
陶晓杨
王祚鹏
徐倩
LI Yong-jun;TAO Xiao-yang;WANG Zuo-peng;XU Qian(School of Earth Science and Resources,Chang an University,Xi'an 710054,Shaanxi,China;Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits of Ministry ofLand and Resources,Xi an 710054,Shaanxi,China)
出处
《地球科学与环境学报》
CAS
北大核心
2019年第1期1-14,共14页
Journal of Earth Sciences and Environment
基金
国家自然科学基金项目(41273033)
新疆维吾尔自治区地质勘查基金项目(Y15-1-LQ01)
关键词
高铝玄武岩
地幔楔
滞后结晶
岛弧
早泥盆世
托让格库都克组
东准噶尔
high-alumina basalt
mantle wedge
delayed crystallization
island arc
Early Devonian
Tuoranggekuduke Formation
East Junggar
