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Ophiolite hosted chromitite formed by supra-subduction zone peridotite –plume interaction
Geoscience Frontiers ( IF 8.9 ) Pub Date : 2020-05-19 , DOI: 10.1016/j.gsf.2020.05.005
Júlia Farré-de-Pablo , Joaquín A. Proenza , José María González-Jiménez , Thomas Aiglsperger , Antonio Garcia-Casco , Javier Escuder-Viruete , Vanessa Colás , Francisco Longo

Chromitite bodies hosted in peridotites typical of suboceanic mantle (s.l. ophiolitic) are found in the northern and central part of the Loma Caribe peridotite, in the Cordillera Central of the Dominican Republic. These chromitites are massive pods of small size (less than a few meters across) and veins that intrude both dunite and harzburgite. Compositionally, they are high-Cr chromitites [Cr# ​= ​Cr/(Cr ​+ ​Al) atomic ratio ​= ​0.71–0.83] singularly enriched in TiO2 (up to 1.25 ​wt.%), Fe2O3 (2.77–9.16 ​wt.%) as well as some trace elements (Ga, V, Co, Mn, and Zn) and PGE (up to 4548 ​ppb in whole-rock). This geochemical signature is unknown for chromitites hosted in oceanic upper mantle but akin to those chromites crystallized from mantle plume derived melts. Noteworthy, the melt estimated to be in equilibrium with such chromite from the Loma Caribe chromitites is similar to basalts derived from different source regions of a heterogeneous Caribbean mantle plume. This mantle plume is responsible for the formation of the Caribbean Large Igneous Province (CLIP). Dolerite dykes with back-arc basin basalt (BABB) and enriched mid-ocean ridge basalt (E-MORB) affinities commonly intrude the Loma Caribe peridotite, and are interpreted as evidence of the impact that the Caribbean plume had in the off-axis magmatism of the back-arc basin, developed after the Caribbean island-arc extension in the Late Cretaceous. We propose a model in which chromitites were formed in the shallow portion of the back-arc mantle as a result of the metasomatic reaction between the supra-subduction zone (SSZ) peridotites and upwelling plume-related melts.



中文翻译:

超俯冲带橄榄岩-泡沫相互作用形成的蛇绿岩型铬铁矿

在橄榄岩典型suboceanic地幔(托管铬铁机构SL蛇绿岩)在洛马加勒比橄榄岩的北部和中部部分发现,在多米尼加共和国的中央山脉。这些铬铁矿是块状的豆荚,小而小(跨度不到几米),并且侵入了褐铁矿和哈兹伯格岩。从成分上讲,它们是高铬铬铁矿[Cr#= Cr /(Cr + Al)原子比= 0.71-0.83]富含TiO 2(最高1.25 wt。%),Fe 2 O 3(2.77–9.16 wt。%)以及一些微量元素(Ga,V,Co,Mn和Zn)和PGE(整块岩石中高达4548 ppb)。对于地球上地幔中的铬铁矿来说,这种地球化学特征是未知的,但类似于从地幔羽衍生的熔体中结晶的铬铁矿。值得注意的是,据估计与Loma Caribe铬铁矿中的亚铬铁矿处于平衡状态的熔体类似于衍生自加勒比地幔柱不同来源区域的玄武岩。这种地幔柱负责形成加勒比大火成岩省(CLIP)。具有弧后盆地玄武岩(BABB)和丰富的中海脊玄武岩(E-MORB)亲和性的白云岩堤坝通常侵入洛马加勒比海橄榄岩,并且被解释为加勒比羽对离轴岩浆作用的影响的证据。后弧盆地 在白垩纪晚期加勒比海岛屿弧扩展之后发展起来。我们提出了一个模型,其中超俯冲带(SSZ)橄榄岩和上升流相关的熔体之间的交代反应,在后弧地幔的浅部形成了铬铁矿。

更新日期:2020-05-19
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