Intermediate chromitite in Kızıldağ ophiolite (SE Turkey) formed during subduction initiation in Neo-Tethys
Intermediate chromitite in Kızıldağ ophiolite (SE Turkey) formed during subduction initiation in Neo-Tethys
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克孜勒达蛇绿岩（土耳其东南部）中的中铬铁矿是在新特提斯洋俯冲起始过程中形成的
DOI：
10.1016/j.oregeorev.2018.10.004
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发表时间：
2019-01
影响因子：
3.3
通讯作者：
Kapsiotis Argyris
中科院分区：
文献类型：
--
作者：
Chen Chen;Su Ben-Xun;Xiao Yan;Pang Kwan-Nang;Robinson Paul T;Uysal Ibrahim;Lin Wei;Qin Ke-Zhang;Avcı Erdi;Kapsiotis Argyris
克孜勒达佩斯蛇绿岩中的铬铁矿主要产于地幔方辉橄榄岩中，部分产于壳层堆晶纯橄榄岩中。纯橄榄岩和铬铁矿中的橄榄石都是高镁的（Fo分别为90.5-92.8和90.2-96.1），而共存的铬铁矿在成分上变化很大（Cr#分别为52.9-68.6和57.1-76.2），使其介于高铝和高铬品种之间。铬铁矿中Ni、V和Ga的浓度（Ni：741-1310 ppm; V：521-1227 ppm; Ga：20-51 ppm）也是高度可变的，跨越高Al和高Cr铬铁矿的范围。纯橄榄岩和铬铁矿中的橄榄石具有大范围的Li浓度（0.27-2.47 ppm）和δ 7 Li值（−7.20-29.90‰）。基于计算的Al 2 O3（12.1-17.2 wt.%）纯橄榄岩和铬铁岩的母岩浆含量、FeO/MgO值（0.92-1.57）和微量元素含量表明，它们是介于MORB和玻安质熔体之间的过渡岩浆，是由不同来源的部分熔融产生的地球化学和空间上不同的岩浆混合而成。纯橄榄岩和铬铁矿（KZ 14 -38和KZ 15 -38除外）中橄榄石的Li同位素组成既不受扩散控制，也不受分离结晶控制，可能是其母体熔体的固有特征。纯橄榄岩和铬铁矿中橄榄石的δ 7 Li值范围与弧熔岩和海相沉积物中的δ 7 Li值范围相似，表明铬铁矿记录了不同程度的熔体渗透。广泛的锂同位素变化的橄榄石和化学的铬铁矿从KızıldaExpense铬铁矿表明，父母的熔体起源于一个原弧前地幔俯冲开始。
Chromitites in the Kızıldağ ophiolite mostly occur in the mantle harzburgites and some of them in crustal cumulate dunites. Olivine in both the dunites and chromitites is highly magnesian (Fo = 90.5–92.8 and 90.2–96.1, respectively), while the coexisting chromite varies widely in composition (Cr# = 52.9–68.6 and 57.1–76.2, respectively), placing it between high-Al and high-Cr varieties. Concentrations of Ni, V and Ga in the chromite (Ni: 741–1310 ppm; V: 521–1227 ppm; Ga: 20–51 ppm) are also highly variable, straddling the range of high-Al and high-Cr chromite. Olivine in the dunites and chromitites has a large range of Li concentrations (0.27–2.47 ppm) and δ7Li values (−7.20–29.90‰). Based on the calculated Al2O3(12.1–17.2 wt.%) contents, FeO/MgO values (0.92–1.57) and trace element concentrations of the parental magmas of the dunites and chromitites, it is suggested that they are transitional between MORB and boninitic melts, and should have been derived by mixing of geochemically and spatially distinct magmas generated by partial melting of different sources. The Li isotopic compositions of olivine from the dunites and chromitites (except KZ14-38 and KZ15-38) are neither controlled by diffusion nor fractional crystallization, and thus may be intrinsic features of their parental melts. The range of δ7Li values of olivine in the dunites and chromitites is analogous to that of arc lavas and marine sediments, indicating that the chromitites record various degrees of melt penetration. The wide range of Li isotopic variations in olivine and chemistry in chromite from the Kızıldağ chromitites suggest that the parental melts were originated in a proto-forearc mantle during subduction initiation.
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作者：
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通讯作者：
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