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Chromite-bearing quartzite in the southern fringe of Singhbhum Craton around Ghutrigaon, Eastern India: Petrogenetic implication
Geological Journal ( IF 1.4 ) Pub Date : 2021-02-25 , DOI: 10.1002/gj.4107
Asish K. Das 1 , Somnath Khaoash 1 , Patitapaban Mishra 1 , Birendra K. Mohapatra 1 , Jayakrushna Mohanty 2
Affiliation  

The chromite mineralization in the southern fringe of the Singhbhum Craton around Ghutrigaon, Dhenkanal district, Odisha, Eastern India shows a unique nature of occurrence. The structural features, mineral assemblage, and spinel composition are different from the two well-known Sukinda and Boula-Nuasahi chromite deposits occurring within the mafic/ultramafic complex in Odisha. The chromite-bearing quartzite from Ghutrigaon shows typical sedimentary features, such as colour banding, cross-bedding, broomsticks, and slump structures and is closely associated with large volumes of volcanic tuff. The chromite-bearing quartzite contains major quartz and chromite along with minor accessories such as fuchsite, chromian muscovite, chromphyllite, chromceladonite, chromechalcedony, rutile, and zircon. Detailed mineralogical, textural, and spinel compositional analysis support to its detrital origin having been derived from a volcanic source. The Cr-spinel composition shows very low Mg-number (0.01–0.04) and high Cr-number (0.69–0.79) in contrast to chrome ores from different localities of India. The EPMA results when plotted in various established discrimination diagrams show a distinctly different domain, indicating that these are affected by a pro-grade metamorphic event. Our study shows that the Ghutrigaon chromite ore owes a mixed origin where chromite detritus from a volcanic provenance (island arc to intra-plate terrain) got deposited along with terrestrially derived silica-rich clastics. Paucity in magnesium content in the spinel may be the result of replacement of Mg by Fe2+ due to compositional re-equilibration during metamorphism. Grain coarsening took place at the onset of metamorphism. The volcaniclastics added to the arenaceous sediment gave rise to different Al-silicate minerals. The chrome-content in most of these minerals is attributed to redistribution of Cr through solid-state diffusion during metamorphism. Rutile and Zircon detritus are considered as continental input. The presence of Zn, Mn, and Ni in the chrome spinel is most likely contributed by the precursor rock. The formation of large idioblastic chromite grains, preferred grain orientation, band development, elevated values of some elements in the spinel, Zn in particular attest to their formation under low-grade regional metamorphism (greenschist facies).

中文翻译:

印度东部 Ghutrigaon 周围 Singhbhum Craton 南缘的含铬石英岩:岩石成因意义

印度东部奥里萨邦 Dhenkanal 区 Ghutrigaon 周围 Singhbhum Craton 南缘的铬铁矿矿化显示出独特的产地性质。构造特征、矿物组合和尖晶石成分与奥里萨邦镁铁质/超镁铁质复合体中出现的两个著名的 Sukinda 和 Boula-Nuasahi 铬铁矿矿床不同。Ghutrigaon含铬石英岩具有典型的沉积特征,如色带、交错层理、扫帚柄和塌落结构,与大量火山凝灰岩密切相关。含铬铁矿的石英岩包含主要的石英和铬铁矿,以及次要的辅料,如紫石英、铬白云母、铬蜡石、铬青石、铬玉髓、金红石和锆石。详细的矿物学、质地、和尖晶石成分分析支持其碎屑来源来自火山源。与印度不同地区的铬矿石相比,Cr 尖晶石成分显示出非常低的 Mg 值 (0.01-0.04) 和高 Cr 值 (0.69-0.79)。EPMA 结果绘制在各种已建立的鉴别图中时显示出明显不同的域,表明这些域受到亲级变质事件的影响。我们的研究表明,Ghutrigaon 铬铁矿具有混合成因,其中来自火山源(岛弧到板内地形)的铬铁矿碎屑与来自陆地的富含二氧化硅的碎屑一起沉积。尖晶石中镁含量的缺乏可能是由于 Fe 取代了 Mg 与来自印度不同地区的铬矿石相比,Cr 尖晶石成分显示出非常低的 Mg 值 (0.01-0.04) 和高 Cr 值 (0.69-0.79)。EPMA 结果绘制在各种已建立的鉴别图中时显示出明显不同的域,表明这些域受到亲级变质事件的影响。我们的研究表明,Ghutrigaon 铬铁矿具有混合成因,其中来自火山源(岛弧到板内地形)的铬铁矿碎屑与来自陆地的富含二氧化硅的碎屑一起沉积。尖晶石中镁含量的缺乏可能是由于 Fe 取代了 Mg 与印度不同地区的铬矿石相比,Cr 尖晶石成分显示出非常低的 Mg 值 (0.01-0.04) 和高 Cr 值 (0.69-0.79)。EPMA 结果绘制在各种已建立的鉴别图中时显示出明显不同的域,表明这些域受到亲级变质事件的影响。我们的研究表明,Ghutrigaon 铬铁矿具有混合成因,其中来自火山源(岛弧到板内地形)的铬铁矿碎屑与来自陆地的富含二氧化硅的碎屑一起沉积。尖晶石中镁含量的缺乏可能是由于 Fe 取代了 Mg EPMA 结果绘制在各种已建立的鉴别图中时显示出明显不同的域,表明这些域受到亲级变质事件的影响。我们的研究表明,Ghutrigaon 铬铁矿具有混合成因,其中来自火山源(岛弧到板内地形)的铬铁矿碎屑与来自陆地的富含二氧化硅的碎屑一起沉积。尖晶石中镁含量的缺乏可能是由于 Fe 取代了 Mg EPMA 结果绘制在各种已建立的鉴别图中时显示出明显不同的域,表明这些域受到亲级变质事件的影响。我们的研究表明,Ghutrigaon 铬铁矿具有混合成因,其中来自火山源(岛弧到板内地形)的铬铁矿碎屑与来自陆地的富含二氧化硅的碎屑一起沉积。尖晶石中镁含量的缺乏可能是由于 Fe 取代了 Mg2+由于变质过程中的成分重新平衡。晶粒粗化发生在变质作用开始时。添加到砂质沉积物中的火山碎屑产生了不同的铝硅酸盐矿物。大多数这些矿物中的铬含量归因于变质过程中通过固态扩散的 Cr 重新分布。金红石和锆石碎屑被视为大陆输入。铬尖晶石中 Zn、Mn 和 Ni 的存在很可能是由前体岩石贡献的。大的特异母粒铬铁矿颗粒的形成、优选的晶粒取向、谱带发展、尖晶石中某些元素的升高值,尤其是 Zn,证明它们是在低品位区域变质作用(绿片岩相)下形成的。
更新日期:2021-02-25
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