摘要
二叠纪是塔里木盆地热-构造演化史上最重要的时期,这一时期在塔里木盆地中部和西北部发生了大规模的基性-中酸性岩浆活动。对塔里木盆地西北部瓦吉里塔格超镁铁岩的地球化学反演表明:瓦吉里塔格超镁铁岩(包括角砾和胶结物)是由残余岩浆和橄榄石、单斜辉石不同比例混合的产物,其中角砾主要由橄榄石和残余岩浆组成,其比例达到了72∶28。与角砾中橄榄石(平均Fo=0.82)平衡的熔体的w(MgO)为9.06%、w(FeOt)为11.77%,是由w(MgO)为11.46%、w(FeOt)为12.12%的原始岩浆经7.3%的橄榄石(Fo=0.82)分异而成的。其原始岩浆并不属于高镁岩浆,而是地幔石榴子石橄榄岩低程度(<5%)部分熔融的产物,初始熔融温度约1150～1250℃,压力约2.2GPa,深度约70km。结合前人研究成果认为,塔里木盆地二叠纪岩浆活动的形成可能与软流圈上涌导致的软流圈-岩石圈的相互作用有关,目前尚没有直接的岩石地球化学证据表明有地幔柱活动的参与。
The Permian era is the most important stage during the thermal-tectonic evolution of the Tarim basin. During this stage, huge volumes of marie and mid-acid magmas were formed. Geochemical inversion of ultramafic rocks from Wajilitag, NW Tarim basin, indicates that these rocks （including the breccias and bindings） are composed of residual magma, olivine and pyroxene with different ratios. The breccias are mainly composed of olivine and residual magma with ratio up to 72 ： 28. The MgO and FeOt contents of the equilibrium magma （corresponding to olivine with F0 = 0.82） are 9.06% and 11. 77%, respectively, and it was produced by primary magma MgO= 11.46 % and FeOt= 12.12 % ） under 7.3 fractidnation of olivine （F0=0.82）. The primary magma was originated from low degree partial melting （〈5%） of garnet bearing mantle peridotite instead of the high Mg magma. The original melting temperature was 1 150 - 1 250℃, and the pressure was 2. 2 GPa, corresponding to 70 km deep. Combined with previous studies, it＇s concluded that the Permian magmatism in Tarim basin was probably formed by the interaction of asthenosphere and lithosphere that was triggered by the upwelling of the asthenospheric mantle, and there was no direct petro-geochemical evidence to support the mantle plume hypothesis.
出处
《吉林大学学报（地球科学版）》
EI
CAS
CSCD
北大核心
2010年第6期1301-1310,1322,共11页
Journal of Jilin University：Earth Science Edition
基金
中国科学院知识创新项目(KZCX2-YW-128)
宿州学院教授(博士)科研启动基金项目(2009jb04)
