摘要
元古代和早古生代是北秦岭两个主要的火山岩浆作用时期,地球化学研究表明,元古代基性火山岩具有相对低SiO_2、Al_2O_3和高TiO_2特征,基性火山岩TiO_2-P_2O_5、MgO/FeO-Y、的变化显示了正常的、稳定的岩浆作用过程,相容元素分配模型表明这一时期基性火山岩与华北区上地幔部分熔融岩浆作用相吻合,早古生代基性火山岩除普遍具有高、低特征外,突出地表现出地球化学成分的不均匀性,多源、混合岩浆作用的干扰使单源岩浆演变特征遭受破坏,相容元素分配模型表明:这一时期基性火山岩浆与引起秦岭区、华北区上地幔岩浆共同作用有关系,北秦岭基性火山岩浆作用的特征与这一地区从元古代到早古生代的构造发展是相适应的,反映了该区上地幔性质及岩石圈构成的重大改变。
The Proterozoic and Early Palaeozoic were two main periods of volcanic-magmatism in Northern Qinling. It would be possible for the basic volcanic rocks to provide the important information from upper mantle magmatic sources. The Proterozoic basic volcanic rocks had relative low SiO2, A12O3 and high TiO2 , and showed a normal and stable mag-matism in terms of the various relation of TiO2-P2O5, MgO/FeO*-Y and MgO/FeO*-REE. The distribution model of compatible elements applied to the upper mantle partial melt in North China appears to be consistent with the composition of the basalt in the Proterozoic. The Early Palaeozoic basic volcanic rocks had, in addition to high A12O3 and low TiO2, marked nonhomogeneity in their chemical composition, it seems that polygene and mixed magma would cause complicated change of composition relation in magmatic evolution as only single-source. Compatible element distribution model of polygene magma, derived separately from the upper mantle of North China and Northern Qinling, is identical with composition character of the Early Paleozoic. The basic volcanic magmaism in Northern Qinling is related to tectonic development from the Proterozoic to the Early Palaeozoic in the area. It reflects, to a great extent, reformation of the upper mantle and the litho-sphere in Northern Qinling during the two periods. Sr isotope composition also provides the further evidence for the above statement.
出处
《地球科学（中国地质大学学报）》
EI
CAS
CSCD
北大核心
1993年第1期73-83,共11页
Earth Science-Journal of China University of Geosciences
基金
地矿部"七五"秦巴重大项目二级课题"秦巴区域地球化学"
国家自然科学基金488150项资助
关键词
火山岩
地球化学
上地幔
岩浆作用
basic volcanic rocks, geochemistry, the upper mantle magmatic source, Northern Qinling.
