第27卷第3期 2013年6月
现代地质 GEOSCIENCE
Vol. 27No. 3
Jun.2013
西南印度洋中脊49.6°E和50.5°E区玄武岩
岩石学及元素地球化学特征
于森，苏新，陶春辉2，武光海，李怀明，娄汉林
（1.中国地质大学海洋学院，北京100083；2.国家海洋局第二海洋研究所国家海洋局海底科学重点实验室，浙江杭州310012）摘要：对近年来我国"大洋一号"科考船在西南印度洋中脊（SWIR)多金属硫化物调查区4个站位所获得的玄武岩进行了岩石学及元素地球化学研究。其岩相学特征为以斑状结构为主，斑晶矿物主要由斜长石、辉石和榄石组成。基质以间隐结构为主，主要由斜长石、橄榄石和辉石微晶组成。全岩元索地球化学分析结果表明样品属于亏损型洋中脊玄武岩。矿物化学成分表明斜长石主要为倍长石和拉长石，橄榄石为贵撤榄石。研究区玄武岩具低的Na,、K/Ti比值和 LREE/HREE以及较高的Fe值，可整体归人SWIR49°E-70°E区指示岩浆熔融程度最高、熔融深度最深的区域内。本次研究为探索SWIR洋脊玄武岩和岩浆熔融等相关研究提供了49.6°E和50.5°E区的新资料，也指示了区内岩浆活动或成矿围岩物质来源的复杂性，
关键调：洋中脊玄武岩；岩石学；矿物学；元索地球化学：西南印度洋中脊
中图分类号：P588.14*5
文献标志码：A
文章编号：10008527(2013)03-049712
Petrological and Geochemical Features of Basalts at 49.6°E and 50.5°E
HydrothermalFieldsalongtheSouthwestIndianRidge
YU Miao', SU Xin', TAO Chun-hui?, WU Guang-hai°, LI Huai-ming", LOU Han-lin
(1. School of Ocean Sciences, Ching Unitersity of Geosciences, Bejing100083, China;
2. Key Laboraiory of Submarine Geosciences, Second Institute of Oceanography, Stalte Oeeanic Administration, Hangzhou, Zhejiang310012, China Abstract: We analyzed basalt samples from 4 sites at 49. 6°E and 50. 5°E along the Southwest Indian Ridge, which were collected with television-video guided grab (TVG ) or dredge (D ) during 2 hydrothermal expedi-tions of Chinese vessel "Da Yang Yi Hao" in 2008 and in 2010. These samples are fragments of basaltic pillow lavas and sheet flows. These samples are mainly porphyritic with fine-grained, and euhedral to anhedral pheno crysts of plagioclase, olivine and pyroxene. The matrix contains microcrystalline plagioclase, olivine and pyrox ene, in which tabular plagioclase microphenocrysts occur with a radical texture. Whole rock major and rare earth elements data of these samples show that ratios of K/Ti range from 0. 071 to 0. 091, and La/Sm from 0. 52 to 0. 70, suggesting that they are normal mid-ocean ridge basalt ( N-MORB). Plagioclase compositions range from An7%-7s to Ang6, while those of olivine range from Fogs to Fog4- In comparison of earlier study on basalt samples along SWIR (49°E -70°E), samples in this study are featured with much more depletion in light rare earth elements, Na, and K/Ti, but higher Fes. These data indicate that mantle melting in the study area occu in higher degree and at deeper depth. Furthermore, petrologic and mineralogic features of basalts at 49. 6°E and 50. 5°E suggest that magma activity and source in the study area are complex.
收稿日期：2012-12-01；改回日期：2013-03-28；贵任编辑：楼亚儿。
基金项目：中国大洋协会项目(DYXM-115-02-1-05，DY125-11-R-01-01)。
作者简介：于森，男，博士研究生，1985年出生，海洋地质专业，主要从事深海岩石学、矿物学方面的研究。
Email;yumiaol04@gmailL com
通信作者：苏新，女，教授，博士生导师，1957年出生，地层古生物专业，主要从事钙质超微化石、海洋地质和海洋气体水
合物方面的研究。Email：xsu@cugh.edu.cn。