Journal of Earth System Science ( IF 1.3 ) Pub Date : 2023-09-23 , DOI: 10.1007/s12040-023-02173-3
Saptarshi Mallick , Arup Ratan Manna , J P Mohakul
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Abstract
Singhbhum Craton (SC), one of the oldest continental crusts, has a nucleus of Singhbhum Granite Complex with volcano-sedimentary belts in peripheral parts. Deciphering the inter-relationship between volcano-sedimentary packages and surrounding granitoids offers considerable challenges. The present study area lies in the northwestern parts of SC. Lithounits of volcano-sedimentary packages drapes around the Paleoarchean Bonai Granite Complex (BGC). An attempt has been made to understand the basin development over BGC based on the mutual relationship between lithopackages of Iron Ore Group (IOG) and their structural disposition. It is proposed that two distinct basins, Koira and Gurundia, developed over BGC during Mesoarchean. While the Eastern Koira basin witnessed continuous development accompanied by subsidence wherein lithopackages of Bonai–Kendujhar Iron-ore Belt were deposited, Western Gurundia Basin is marked by a hiatus after the deposition of Gurundia quartzite and mafic volcanics in a shoreline to shallow marine environment. Darjing Group of rocks deposited as platformal package over Gurundia, Koira groups and BGC. Litho packages of Koira, Gurundia and Darjing groups exhibit structural unity as they co-deformed during Iron ore orogeny. The first deformation phase has led to a series of NE–SW to ENE–WSW trending low plunging overturned folds with southeasterly vergence. The second deformation, near coaxial with the first, has led to low northerly plunging open folds with steep northwesterly dipping axial planes. BGC occupies the core of a major second-generation fold with volcano-sedimentary sequence draping around it. It is proposed to put them under Iron Ore Super Group (IOSG), where IOGs (Koira and Gurundia groups) represent the lower part and Darjing Group as the upper part.
Research Highlights
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IOSG consists of IOGs (Koira and Gurundia groups) and Darjing Group as per present observation.
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Volcano sedimentary litho packages of IOG were deposited in two distinct basins (Koira and Gurundia basins) developed over BGC in a continental shelf-slope facies.
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Darjing Group deposited all over Gurundia and Koira groups and BGC after a hiatus which is marked by polymictic basal conglomerate.
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All the litho members of IOSG were co-deformed during Iron-Ore Orogeny (during the formation of Ur) and exhibit two distinct phases of folding as observed from field and this is reported for the first time with an attempt to bring Darjing group within Iron Ore Supergroup (IOSG).
中文翻译：
印度辛布胡姆克拉通博奈花岗岩杂岩边缘太古代绿岩带的演化历史及其地层对比
摘要
Singhbhum 克拉通 (SC) 是最古老的大陆地壳之一，其核心为 Singhbhum 花岗岩杂岩，外围为火山沉积带。破译火山-沉积物包与周围花岗岩之间的相互关系面临着相当大的挑战。目前的研究区位于南卡罗来纳州西北部。火山沉积岩群覆盖在古太古代博奈花岗岩杂岩（BGC）周围。试图根据铁矿石群（IOG）岩石包之间的相互关系及其构造配置来了解BGC盆地的发育。有人提出，在中太古代期间，BGC 上发育了两个不同的盆地：科伊拉盆地和古隆迪亚盆地。东科伊拉盆地经历了持续发展并伴随着沉降，其中沉积了博奈-肯杜贾尔铁矿带的岩石包，而西古伦迪亚盆地则在古伦迪亚石英岩和镁铁质火山岩在海岸线到浅海环境中沉积后出现了中断。大金群岩石以平台包形式沉积在古伦迪亚群、科伊拉群和 BGC 上。Koira、Gurundia 和 Darjing 群的石刻包在铁矿石造山运动期间共同变形时表现出结构统一性。第一个变形阶段导致了一系列 NE-SW 到 ENE-WSW 趋势的低倾倒翻转褶皱，并向东南辐辏。第二次变形与第一次变形几乎同轴，导致了向北倾斜的低张开褶皱和向西北倾斜的轴面。BGC 占据了第二代主要褶皱的核心，火山沉积序列覆盖在其周围。建议将它们归入铁矿石超级集团（IOSG），其中IOG（Koira和Gurundia集团）代表下部，大金集团代表上部。
研究亮点
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根据目前的观察，IOSG 由 IOG（Koira 和 Gurundia 组）和 Darjing 组组成。
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IOG 火山沉积岩相沉积于 BGC 之上大陆架斜坡相中发育的两个不同盆地（Koira 和 Gurundia 盆地）中。
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在以多聚基底砾岩为标志的中断之后，大金群沉积在整个古伦迪亚群、科伊拉群和 BGC 上。
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IOSG 的所有石刻成员在铁矿石造山运动期间（乌尔形成期间）共同变形，并从现场观察到表现出两个不同的折叠阶段，这是首次报道，试图将 Darjing 群纳入铁矿内部矿石超群（IOSG）。
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