白云鄂博地区碳酸岩脉侵位序列与稀土元素富集机制   总被引：5，自引：2，他引：3  

杨奎锋  范宏瑞  胡芳芳  王凯怡 《岩石学报》2010,26(5):1523-1539

白云鄂博地区发育大量的火成碳酸岩脉。按照矿物组成,碳酸岩脉可分为白云石型、白云石-方解石共存型和方解石型。野外穿插关系表明,白云石型碳酸岩脉形成得早,而方解石型碳酸岩脉形成得晚。白云鄂博地区的碳酸岩浆存在由白云石型到共存型再到方解石型的先后结晶顺序和演化趋势。碳酸岩脉的主量、稀土和微量元素组成特征表明,随着碳酸岩脉中方解石矿物组分的增加,轻稀土元素的含量呈明显富集趋势,而长期的结晶分异作用正是稀土元素,尤其是轻稀土元素在晚期岩浆中强烈富集的内在机制。  相似文献   

Carboniferous subvolcanic activity on the Beara Peninsula,SW Ireland     

M. Pracht  J. A. Kinnaird 《Geological Journal》1997,32(4):297-312

Magmatic activity associated with the Munster Basin has been more widespread than previously reported. The Munster Basin is a substantial sedimentary basin, and towards the end of its extensional phase of development, at the beginning of the Variscan orogeny in Ireland, numerous intrusions were emplaced into consolidated Upper Devonian and Lower Carboniferous sediments on the Beara Peninsula. One hundred and sixty-four sills and dykes have been mapped which are subalkaline to alkaline in nature. Two separate suites have been identified. The northern suite comprises subalkaline basalts of Cod's Head and Dursey Island which are intruded into Devonian Red Beds, and the southern suite comprises alkali basalts, trachytes and phonolites which crop out along 9 km of the south coast of the Beara Peninsula and are suggested as Brigantian in age. They are intruded into Devonian Red Beds and marine Lower Carboniferous strata and are therefore later than the tholeiitic magmatism on the Iveragh peninsula to the north. The alkaline magmatism on Beara was induced by lithospheric thinning and controlled partly by pre-existing zones of weakness in the Caledonide crust and partly by fracture zones that developed parallel to the Munster Basin margin as it subsided. In contrast to the Iveragh Peninsula, the stretching factor for the Beara lithosphere was never large enough to lead to the production of tholeiitic magmas. © 1997 John Wiley & Sons, Ltd.  相似文献   

西藏南部绒布地区基性岩脉岩石地球化学、年代学特征及地质意义   总被引：1，自引：0，他引：1  

丁枫  高建国  徐琨智 《岩石学报》2020,36(2):391-408

绒布地区位于西藏南部特提斯喜马拉雅构造域中段北缘,夹持于北侧邛多江断裂和南侧的绒布-古堆断裂之间。该地区发育大量的基性岩脉。通过岩石学、年代学及岩石地球化学等方面的研究,认为区内出露的基性岩脉类型为辉绿玢岩、辉长辉绿岩及辉长岩等。辉绿玢岩结晶年龄为137. 3±1. 6Ma,具有E-MORB的特征,未遭受岩石圈地幔或地壳混染,主要形成于大洋板内环境,受洋中脊源区的影响明显。辉长辉绿岩、辉长岩结晶年龄为147. 3±3. 6Ma,与时代接近的拉康组、桑秀组基性火山岩具有相同OIB的地球化学特征,带有岩石圈地幔物质混染的痕迹,形成于强烈拉伸的大陆边缘裂谷环境。晚侏罗世-早白垩世特提斯喜马拉雅被动陆缘处于强烈拉伸、岩石圈减薄的构造背景之下,OIB型辉长辉绿岩及辉长岩与措美大火成岩省诸多OIB型基性岩具有相似岩石成因,是大陆裂谷背景下Kerguelen地幔柱与岩石圈地幔相互作用的产物;而E-MORB型辉绿玢岩则可能是靠近大陆边缘的热点以下地幔柱与软流圈地幔相互作用的产生的岩浆沿区域深大断裂运移至大陆边缘侵位的结果。OIB型辉长辉绿岩、辉长岩的结晶年龄明显早于Kerguelen地幔柱活动的峰期(132Ma),可能是地幔柱早期活动的产物; E-MORB型辉绿玢岩的存在可作为目前对于措美大火成岩省基性岩脉类型的补充,对认识措美大火成岩省具有一定的意义。  相似文献