Title Two stages of immiscible liquid separation in the formation ofPanzhihua-type Fe-TiV oxide deposits
Title Two stages of immiscible liquid separation in the formation ofPanzhihua-type Fe-TiV oxide deposits
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发表时间：
2013
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通讯作者：
Mei‐Fu Zhou;W. Chen;C. Wang;S. Prevec;P. Liu;G. Howarth
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作者：
Mei‐Fu Zhou;W. Chen;C. Wang;S. Prevec;P. Liu;G. Howarth
峨眉山大火成岩省（ELIP）中的岩浆氧化物矿床是重要的铁、钛、钒矿源。攀枝花、红格、白马等大型岩浆Fe-Ti-V氧化物矿床产于ELIP中部攀西地区的层状镁铁质-超镁铁质岩体中。同样类型的ELIP相关矿床也出现在遥远的南方，包括攀枝花以南约130公里的安义存款和红河断裂带的棉花地存款。安义存款是相对较小的，但类似的托管在层状镁铁质侵入体。棉花地存款的锆石U-Pb年龄为w260 Ma，与ELIP同时代。该存款是在印支期造山和红河断裂作用下变质形成的。棉花地存款磁铁矿中Ti、V含量较低，可能与后期变质作用有关。氧化物矿床的分布与ELIP的穹隆构造无关。ELIP中所有氧化物矿床的一个主要特征是含氧化物辉长岩侵入体、正长岩体和高钛溢流玄武岩的空间组合。因此，我们建议，从地幔柱岩浆侵位到一个浅岩浆房，在那里他们演变成一个领域的液体不可渗透性，形成两种硅酸盐液体，一个非常铁-蒂里奇辉长岩组成和其他正长岩。然后，不混溶的Fe-Ti-（P）氧化物熔体可以从镁铁质岩浆中分离出来，形成氧化物沉积物。形成这些矿床的母岩浆可能是富铁-钛苦橄岩，来自比产生含硫化物侵入体的岩浆更深的富集软流圈地幔
Magmatic oxide deposits in the w260 Ma Emeishan Large Igneous Province (ELIP), SW China and northern Vietnam, are important sources of Fe, Ti and V. Some giant magmatic Fe-Ti-V oxide deposits, such as the Panzhihua, Hongge, and Baima deposits, are well described in the literature and are hosted in layered mafic-ultramafic intrusions in the Panxi region, the central ELIP. The same type of ELIPrelated deposits also occur far to the south and include the Anyi deposit, about 130 km south of Panzhihua, and the Mianhuadi deposit in the Red River fault zone. The Anyi deposit is relatively small but is similarly hosted in a layered mafic intrusion. The Mianhuadi deposit has a zircon U-Pb age of w260 Ma and is thus contemporaneous with the ELIP. This deposit was variably metamorphosed during the Indosinian orogeny and Red River faulting. Compositionally, magnetite of the Mianhuadi deposit contains smaller amounts of Ti and V than that of the other deposits, possibly attributable to the later metamorphism. The distribution of the oxide ore deposits is not related to the domal structure of the ELIP. One major feature of all the oxide deposits in the ELIP is the spatial association of oxide-bearing gabbroic intrusions, syenitic plutons and high-Ti flood basalts. Thus, we propose that magmas from a mantle plume were emplaced into a shallow magma chamber where they were evolved into a field of liquid immiscibility to form two silicate liquids, one with an extremely Fe-Tirich gabbroic composition and the other syenitic. An immiscible Fe-Ti-(P) oxide melt may then separate from the mafic magmas to form oxide deposits. The parental magmas from which these deposits formed were likely Fe-Ti-rich picritic in composition and were derived from enriched asthenospheric mantle at a greater depth than the magmas that produced sulfide-bearing intrusions