中文摘要:元古代晋宁期本区发生了一次裂谷一大洋过程，形成扬子板块西部的波动大陆边缘。古生代扬子板块由南向北漂移，寒武纪末一奥陶纪初本区到达南纬9°左右。这时古边界断层重新活动，分异地幔发生2—5％部分熔融所产生并聚集在莫霍面附近的碱性橄榄玄武岩浆沿断裂带上升，形成上部岩浆房。随后岩浆在不同压力下结晶，分别形成基性岩体和基性—超基性岩体；同时由于氧逸度高，铁钛氧化物早期晶出并堆积在岩浆房底部形成早期岩浆矿床。岩浆多次脉动贯入曾使正常的结晶作用多次中断和反复，形成两个以上的Ⅱ级韵律层和相应的钒钛磁铁矿层。由于双扩散作用，结晶锋面以上的岩浆发生对流和分层又使正常的结晶层序复杂化。
Abstract:A rifting-oceanic process which occurred in this area during Proterozoic finning stage formed a passive continental margin in the west of Yangtze plate. The Yangtze plate drifted toward the north during Palaeozoic and the studied area reached 9°south latitude or so at the end of Cambrian and the beginning of Ordovician. As a result of the reactivation of the border faults, the basaltic magma originally concentrated in the deep-seated magma chamber near Moho moved upward along the fault zone and formed quite a few magma chambers in the upper part of the crust. This sort of magma belong to transitional alkali olivine basaltic type, and the REE calculations show that it was produced through 2-5％partial melting of fractionated mantle. The REE contents of the mantle are about 2.3-3.3 times the chondrite vahles. The crystallization of the alkali olivine basaltic magma in the upper chamber was controlled by pressure and oxygen fugacity: layered gabbro-pyroxenite-peridotite intrusions were formed when the pressure was relatively high while layered gabbro intrusions were formed when the pressure was comparatively low. Due to the rather high oxygen fugacity at the beginning of magmatic crystallization, the ferrotitanium oxides of both types of intrusions all crystallized at the early stage and were cumulated on the bottom of the magma chambers, forming early stage magmatic ore deposits. During the magrnatic solidification there were mainly three factors controlling magmatic evolution: (1)fractional crystallization from the bottom upwards, (2)repeated intrusion of magma, (3)double diffusion and magma convection. The fractional crystallization under the high oxygen fugacity condition led to the formation of the early stage magmatic vanadic titanomagnetite beds on the bottom of the cyclic unit and also the regular changes in natural types, textures and structures of the ores. This had something to do with the variation in composition of mineral solid solution series toward lower melting point from bottom to top of the cycle unit and partition and evolution of minor and trace elements. Quite a number of Grade-Ⅱcyclic units and their corresponding vanadic titanomagnetite beds in each intrusion were products of repeated pulsatory magma intrusion during the magmatic differentiation. The composition of the whole intrusion varied toward lower basicity with the gradual increase in residual magma. The double-diffusion and magma convection which occurred at the crystallization front complicated the normal sequence of fractional crystallization and, consequently, facies change and variation in mineral proportion frequently took place in the same horizon, together with the formation of some interbeds, bands and fluidal structures. The above process may be a typical evolution and mineralization process for transitional alkali olivine basaltic magma which was produced along the passive continental margin and was now in upper crustal magma chambers that had different pressures and high oxygen fugacity.
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卢记仁，张光弟，张承信，顾光先，刘玉书，黄与能.1988.攀西层状岩体及钒钛磁铁矿床成因模式[J].矿床地质,7(2):3~11.1988.A genetic model for layered intrusions and vanadic titanomagnetite deposits in Panzhihua-Xichang area[J].Mineral Deposits7(2):3~11
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