Architecture and emplacement of the Nebo–Babel gabbronorite-hosted magmatic Ni–Cu–PGE sulphide deposit, West Musgrave, Western Australia
Architecture and emplacement of the Nebo–Babel gabbronorite-hosted magmatic Ni–Cu–PGE sulphide deposit, West Musgrave, Western Australia
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西澳大利亚西马斯格雷夫 Nebo-Babel 辉长岩岩浆 Ni-Cu-PGE 硫化物矿床的结构和位置
DOI：
10.1007/s00126-007-0123-9
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发表时间：
2007
影响因子：
4.8
通讯作者：
C. Mathison
中科院分区：
文献类型：
--
作者：
Z. Seat;S. Beresford;B. Grguric;Rob S. Waugh;Jon M. A. Hronsky;M. A. Mary Gee;D. Groves;C. Mathison
位于西澳大利亚西马斯格雷夫地块的Nebo-Babel镍铜铂族元素硫化物存款是过去10年中发现的最大的硫化镍矿床。该存款位于一个同心分区的、不含橄榄石的、管状（球粒石）辉长岩侵入体中，该侵入体与Warakurna大火成岩省中约1，078 Ma的Giles复杂层状侵入体有关。Nebo-Babel断错球粒陨石位于无硫化物角闪岩相正片麻岩中，延伸5 km，横截面1 × 0.5 km。火成岩矿物学、组构和结构保存完好。岩石地层学包括在矿化辉长岩（MGN）周围形成外壳的纹理结构的浅色辉长岩（VLGN），以及在陨石中部和下部的贫瘠辉长岩（BGN）和氧化磷灰石辉长岩（OAGN）。矿物和全岩地球化学表明，该单位逐渐演变的顺序：VLGN，MGN，BGN，和OAGN，和不相容的微量元素浓度增加向下的MGN和BGN。矿化作用仅限于早期较原始的单元（VLGN和MGN），以块状硫化物角砾岩和细脉以及浸染型辉长岩型硫化物的形式出现。块状硫化物在侵入序列中侵位较晚，与浸染状硫化物具有不同的铂族元素化学和铜含量，并经历了硫化物分馏。原生岩浆成因的浸染状硫化物的分布与球粒陨石的几何形状和岩浆流动状态有关，而与重力沉降无关。Nebo-Babel存款区不存在含硫围岩，因此，当地地壳的硫添加不太可能是实现硫化物不渗透性的主要机制。Nebo-Babel侵入体是具有多个和相关岩浆脉冲的原始连续岩浆球粒陨石的一部分。母岩浆为中低钾拉斑玄武岩，MgO含量为8- 9wt%。最初的岩浆脉冲（VLGN），最原始和硫化物饱和，可能是侵位沿着在围岩中的线性弱点。VLGN结晶后，稍微更分馏，硫化物饱和岩浆注入通过管道的隔热核心，形成MGN。更分馏的岩浆（BGN）的连续脉冲侵位在侵入体的核心。岩浆流动停止后，封闭系统的晶体分馏产生一致的矿物和化学分馏的趋势在BGN和OAGN。结晶后，侵入体被推翻，然后被詹姆森断层抵消，导致内博-巴别塔明显的“反向”化学和矿物趋势。
The Nebo–Babel Ni–Cu–platinum-group element (PGE) sulphide deposit in the West Musgrave Block, Western Australia, is the largest nickel sulphide discovery in the last 10 years. The deposit is hosted within a concentrically zoned, olivine-free, tube-like (chonolithic), gabbronorite intrusion associated with the, approximately, 1,078-Ma Giles Complex-layered intrusions in the Warakurna large igneous province. Emplaced into sulphide-free amphibolite facies orthogneiss, the fault-offset Nebo–Babel chonolith extends for 5 km and has a cross-section of 1 × 0.5 km. Igneous mineralogy, fabrics, and textures are well preserved. The lithostratigraphy includes variably textured leucogabbronorites (VLGN) that form an outer shell around mineralised gabbronorite (MGN), with barren gabbronorite (BGN) and oxide–apatite gabbronorite (OAGN) in the middle and lower parts of the chonolith. Mineral and whole-rock geochemistry indicate that the units become progressively evolved in the order: VLGN, MGN, BGN, and OAGN, and that incompatible trace-element concentrations increase downwards within the MGN and BGN. The mineralisation, which is confined to the early, more primitive units (VLGN and MGN), occurs as massive sulphide breccias and stringers and as disseminated gabbronorite-hosted sulphides. The massive sulphides were emplaced late in the intrusive sequence, have different PGE chemistry and Cu tenor to the disseminated sulphides, and have undergone sulphide fractionation. The distribution of disseminated sulphides, which are primary magmatic in origin, is related to chonolith geometry and magma flow regimes, rather than to gravitational settling. Sulfur-bearing country rocks are absent in the Nebo–Babel deposit area, and thus, local crustal S addition was unlikely to have been the major mechanism in achieving sulphide immiscibility. The Nebo–Babel intrusion is part of an originally continuous magma chonolith with multiple and related magma pulses. The parental magma was medium- to low-K tholeiite with 8–9 wt% MgO. The initial magma pulse (VLGN), the most primitive and sulphide saturated, was probably emplaced along a linear weakness in the country rock. After crystallisation of VLGN, marginally more fractionated, sulphide-saturated magma was injected through the thermally insulated core of the conduit, forming the MGN. Successive pulse(s) of more fractionated magma (BGN) were emplaced in the core of the intrusion. After magma flow ceased, closed system crystal fractionation produced consistent mineral and chemical fractionation trends within BGN and OAGN. After crystallisation, the intrusion was overturned and then offset by the Jameson Fault resulting in the apparent ‘reverse’ chemical and mineral trends in Nebo–Babel.