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碑坝基性杂岩体由超基性岩、基性岩和脉岩组成,化学成分及微量元素研究表明,它们是同源岩浆形成的,母岩浆属源于上地幔的拉斑玄武岩浆系列,其生成地质环境为活动的大陆边缘及岛弧.岩浆的化学分异趋势主要是向Fe、Na、K富集,少数向Si、Na、K富集,杂岩体的主要部分是一个呈大岩墙状的基性侵入岩.下部岩相由橄榄苏长辉长岩、橄榄辉长岩、苏长辉长岩和辉长岩组成,上部岩相由辉长岩、石英辉长岩及闪长岩组成.从下至上,和Na_2O、K_2O含量上升,而CaO、Al_2O_3含量下降.在下部岩相中有六个层状韵律单元,每一单元由橄榄辉长岩或橄榄苏长辉长岩、苏长辉长岩或辉长岩组成.下部岩相从边缘至中心,矿物及化学成分呈对称性分布.我们认为在岩浆房中曾经有结晶分异作用、岩浆液态化学扩散作用及岩浆对流作用.这些岩浆作用形成了不同的岩相及韵律层状构造.矿物和岩石化学温度计及压力计数据表明,基性岩体形成于1150-1250℃及4-4.5kb条件下.
The basic dam complex is composed of ultramafic rocks, basic rocks and vein rocks. The chemical composition and trace elements show that they are formed by the same magma, the parent magma is derived from the tholeigenic basalt series in the upper mantle, The geological margins and island arcs of the geologic environment are active.The chemical differentiation trend of magma is mainly enriched in Fe, Na and K, and a few are enriched in Si, Na and K. The main part of the complex is a large rock Wall-shaped basic intrusive rocks.The lower facies are composed of olivine-gabbro feldspar, olivine gabbro, so-gabbro feldspar and gabbro, and the upper facies are composed of gabbro, quartz gabbro and diorite From bottom to top, and Na_2O, K_2O contents increased while CaO and Al_2O_3 contents decreased. There are six layered prosodic units in the lower lithofacies, each unit is composed of olivine gabbro or olivine gabbro, Or gabbro.The lower lithofacies distribute symmetrically from the margin to the center, and the minerals and chemical compositions are symmetrical.We think there was crystallization differentiation, magmatic liquid chemical diffusion and magmatic convection in the magma chamber.These magmatism formed Different lithofacies and rhythmic layered structures Data from mineral and petrochemical thermometers and manometers indicate that the mafic rocks are formed at 1150-1250 ° C and 4-4.5 kb.