Petrogenesis and geodynamic setting of high-Cr chromitites in fore-arc peridotites: A case study from the Halaban ophiolite, Eastern Arabian Shield, Saudi Arabia
Petrogenesis and geodynamic setting of high-Cr chromitites in fore-arc peridotites: A case study from the Halaban ophiolite, Eastern Arabian Shield, Saudi Arabia
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弧前橄榄岩中高铬铬铁矿的岩石成因和地球动力学环境：以沙特阿拉伯东阿拉伯地盾哈拉班蛇绿岩为例
DOI：
10.1016/j.lithos.2021.106243
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发表时间：
2021
期刊：
影响因子：
3.5
通讯作者：
K. Al
中科院分区：
文献类型：
--
作者：
H. Gahlan;M. Azer;K. Al
本研究涉及沙特阿拉伯东阿拉伯地盾新元古代哈拉班蛇绿岩的铬铁矿荚和相关地幔部分。 NNW-SSE 走向的哈拉班蛇绿岩代表了适度破碎的彭罗斯型蛇绿岩部分，该部分在构造上位于岛弧组合之上。它包括变辉长岩下方的地幔部分，向上至覆盖镁铁质火山岩的远洋沉积盖层。哈拉班地幔剖面包括含铬铁矿的蛇纹石化超镁铁岩，以及沿着剪切带和断层的变橄榄岩、利斯特维岩和滑石碳酸盐，具有不同程度的蚀变和变质作用。保存下来的纹理包括氟碳铁矿和网格，分别表明所研究的蛇纹岩的方辉橄榄岩和纯铜岩原岩。铬铁矿荚很稀少，仅限于最上地幔部分和上覆莫霍面过渡带（MTZ）纯铜岩。它们通常是块状的，含有间质蛇纹石、碳酸盐和富铬绿泥石（kämmererite）。铬铁矿荚的铬尖晶石含有孤立的硫化物和硅酸盐（蛇纹石、橄榄石和卡默瑞石）内含物。块状铬铁矿的铬尖晶石的 Cr# (0.77–0.83) 和 Mg# (0.60–70) 高于蛇纹岩中浸染的新鲜铬尖晶石核 (Cr# = 0.60–0.70 和 Mg# = 0.43–0.60)。浸染状铬尖晶石的高 Cr# 与低 TiO2 特征 (<0.12 wt%) 相结合，与经历了高度部分熔体萃取的残余地幔岩石一致。哈拉班蛇纹岩和相关铬铁矿豆荚的矿物学特征与最有可能在俯冲带（SSZ）环境的弧前橄榄岩中形成的地幔部分相似。铬铁矿豆荚的铬尖晶石中的高铬#表明可能是胶铜质母岩浆。母岩浆经历了熔体-熔体和熔体-岩石的相互作用，从贫铝、钛和富铬的褐铁矿熔体中沉淀出高铬铬铁矿。值得注意的是，由于铬铁矿形成过程中熔岩反应强度的增加，铬尖晶石的 Cr# 和 Mg# 从方辉橄榄岩通过纯橄榄岩到铬铁矿增加。
The present study deals with chromitite pods and the associated mantle section of the Neoproterozoic Halaban ophiolite, Eastern Arabian shield, Saudi Arabia. The NNW–SSE-trending Halaban ophiolite represents a moderately dismembered Penrose-type ophiolite section that is tectonically emplaced over island arc assemblages. It comprises a mantle section below metagabbros upward to the pelagic sedimentary cover that overlies the mafic volcanics. The Halaban mantle section includes chromitite-bearing serpentinized ultramafics, as well as metaperidotites, listvenites and talc‑carbonates along shear zones and faults with variable degrees of alteration and metamorphism. Preserved textures include bastite and mesh indicating respectively harzburgite and dunite protoliths of the studied serpentinites. The chromitite pods are scarce being restricted to the uppermost mantle section and the overlying Moho transition zone (MTZ) dunite. They are commonly massive with interstitial serpentines, carbonates and Cr-rich chlorite (kämmererite). Cr-spinel of the chromitite pods hosts inclusions of isolated sulfides and silicates (serpentine, olivine and kämmererite). The Cr-spinel of the massive chromitites has higher Cr# (0.77–0.83) and Mg# (0.60–70) than the disseminated fresh Cr-spinel cores in the serpentinites (Cr# = 0.60–0.70 and Mg# = 0.43–0.60). High-Cr# combined with low-TiO2character (<0.12 wt%) of the disseminated Cr-spinel consistent with residual mantle rocks that experienced high degrees of partial melt extraction. The mineralogical features of the Halaban serpentinites and the associated chromitite pods are similar to the mantle section that most probably formed in forearc peridotites of Supra-subduction zone (SSZ) environments. High-Cr# in Cr-spinel of chromitite pods suggesting possible boninitic parent magma. The parent magma had undergone melt–melt and melt–rock interactions with the precipitation of high-Cr chromitite from Al- and Ti-poor, and Cr-rich boninitic melts. Notably, the Cr# and Mg# of Cr-spinel increase from the harzburgite through the dunite to the chromitite due to increase intensity of melt-rock reaction during formation of the chromitite.
沙特阿拉伯西阿拉伯地盾新元古代埃斯蛇绿岩碳化地幔部分含金列表岩的岩石成因
影响因子：
3.5
作者：
Gahlan, Hisham A.;Azer, Mokhles K.;Asimow, Paul D.;Al-Kahtany, Khaled M.
通讯作者：
Al-Kahtany, Khaled M.
影响因子：
3.5
作者：
Heba S. Mubarak;M. Azer;A. A. Surour-A.;H. E. Moussa;P. Asimow;M. Kabesh
通讯作者：
Heba S. Mubarak;M. Azer;A. A. Surour-A.;H. E. Moussa;P. Asimow;M. Kabesh