Chromitite genesis based on chrome-spinels and their inclusions in the Sartohay podiform chromitites in west Junggar of northwest China
Chromitite genesis based on chrome-spinels and their inclusions in the Sartohay podiform chromitites in west Junggar of northwest China
复制标题
西准噶尔Sartohay豆状铬铁矿中铬尖晶石及其包裹体的铬铁矿成因
DOI：
10.1016/j.oregeorev.2020.103401
复制
发表时间：
2020-04
影响因子：
3.3
通讯作者：
Zhu Yongfeng
中科院分区：
文献类型：
--
作者：
Zhu Qinmin;Zhu Yongfeng
在准噶尔西部萨托海蛇绿岩浆岩中发现了原生高Al [Cr# = 100 × Cr/(Cr + Al) = 48.2 ~ 54.7]铬铁矿与高Cr （Cr# = 70.9 ~ 80.7）铬铁矿片段偶联。本文报道了两种铬铁矿及其寄主黑土中铬尖晶石的新的岩石学和矿物学数据，以及铬尖晶石中的包裹体，以揭示萨托海铬铁矿的成因。高铝铬铁矿中含有丰富的原生单矿物和多矿物包裹体，包括钠绿云母、顽辉石、透辉石、寄生石、橄榄石、金红石、钛铁矿、硫化物，偶有锆石。这些矿物包裹体的化学成分表明，被捕获的熔体富含H2O、Na2O和TiO2。根据包裹体内矿物相平衡估算的温度和压力分别为812 ~ 992℃和~10.6 kbar。计算出与高铝铬铁矿平衡的母熔体成分（Al2O3= 15.0 ~ 16.1 wt%; TiO2= 0.30 ~ 0.96 wt%; Co = 37.0 ~ 48.2 ppm; Ga = 11.2 ~ 13.3 ppm）表明，这些铬铁矿可能是由类morb熔体与中间贫化的哈茨伯尔矿相互作用形成的。而具有针状斜辉石片层的高铬铬铁矿则完全不含球状含水硅酸盐包裹体。与高铬铬铁矿平衡的亲本熔体成分（Al2O3= 10.3 ~ 12.2 wt%, TiO2= 0.11 ~ 0.26 wt%, Co = 55.8 ~ 60.4 ppm, Ga = 13.4 ~ 17.2 ppm）具有良好的亲合力。我们认为高铬铬铁矿最初形成于与弧相关的环境，然后发生深部再循环和隆升事件，导致高铬铬铁矿作为残块出现在弧后盆地扩张脊中。随后，在Sartohay蛇绿岩中形成高铝铬铁矿，并与先前存在的高铬铬铁矿机械并列。
Primary high-Al [Cr# = 100 × Cr/(Cr + Al) of 48.2–54.7] chromitites coupled with high-Cr (Cr# = 70.9–80.7) chromitite fragments are identified in the podiform chromitites hosted by the Sartohay ophiolitic mélange in west Junggar, northwest China. New petrographic and mineralogical data for chrome-spinels in both types of chromitites and their host harzburgites, as well as inclusions within chrome-spinels, are reported here to reveal the genesis of the Sartohay chromitites. Abundant primary monomineralic and polymineralic mineral inclusions including Na-phlogopite, enstatite, diopside, pargasite, olivine, rutile, ilmenite, sulphide, and occasionally zircon are found in the high-Al chromitites. Chemical compositions of these mineral inclusions indicate that the trapped melts are rich in H2O, Na2O, and TiO2. Temperatures and pressures estimated based on the equilibrium of mineral phases within inclusions are 812–992 ℃ and ~10.6 kbar, respectively. The calculated parental melt compositions (Al2O3= 15.0–16.1 wt%; TiO2= 0.30–0.96 wt%; Co = 37.0–48.2 ppm; Ga = 11.2–13.3 ppm) in equilibrium with high-Al chromitites suggest that these chromitites probably formed by the interaction between MORB-like melts and intermediate depleted harzburgites. In contrast, the high-Cr chromitite fragments with needle-shaped clinopyroxene lamellaes are entirely free of globular hydrous silicate inclusions. The parental melt compositions (Al2O3= 10.3–12.2 wt%; TiO2= 0.11–0.26 wt%; Co = 55.8–60.4 ppm; Ga = 13.4–17.2 ppm) in equilibrium with high-Cr chromitites show boninitic affinity. We propose that the high-Cr chromitites initially formed at an arc-related environment, then the deep recycling and uplift events occurred and resulted in high-Cr chromitites occurring as residual fragments in a back-arc basin spreading ridge. Subsequently, high-Al chromitites were formed and mechanically juxtaposed with the pre-existing high-Cr ones in the Sartohay ophiolitic mélange.
登录
查看更多内容
影响因子：
3.5
作者：
S. Arai;Jiro Uesugi;A. H. Ahmed
通讯作者：
S. Arai;Jiro Uesugi;A. H. Ahmed
影响因子：
1.8
作者：
Zhu Yong
通讯作者：
Zhu Yong
影响因子：
5.8
作者：
H. Prichard;C. Neary;P. Fisher;M. O'hara
通讯作者：
H. Prichard;C. Neary;P. Fisher;M. O'hara
影响因子：
3.1
作者：
F. Costa;M. Dungan;B. Singer
通讯作者：
F. Costa;M. Dungan;B. Singer
影响因子：
6.1
作者：
Shi Chen;Zhaojie Guo;G. Pe‐Piper;Bei Zhu
通讯作者：
Shi Chen;Zhaojie Guo;G. Pe‐Piper;Bei Zhu