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首页> 外文期刊>Journal of Asian earth sciences >Tattekere conglomerate-quartzite association: origin and stratigraphic position of a disputed Archean formation in the supracrustals of Karnataka, India
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Tattekere conglomerate-quartzite association: origin and stratigraphic position of a disputed Archean formation in the supracrustals of Karnataka, India

机译：Tattekere砾岩-石英岩协会：印度卡纳塔克邦地壳上有争议的太古宙地层的起源和地层位置

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摘要

The origin and stratigraphic interpretation of the conglomerate-quartzite rocks occurring in and around Tattekere and Kumkumna Hosuru villages in the Holenarsipur Supracrustal Belt, is an important aspect of the Precambrian Geology of Karnataka, India. Due to the controversy regarding its origin and stratigraphic status, the geology of the Holenarsipur Supracrustal Belt has been interpreted by previous workers in different ways. In the present work, attempts have been made to resolve the controversy based on recent observations and analytical results. The petrographic characteristics of conglomerates and quartzites, the occurrences of primary sedimentary structures and their similarity to proven sedimentary quartzites in the northern sector, along with the chemical composition of the quartzites point to a sedimentary origin for this association. The heavy mineral and chemical composition of the quartzites suggest a major source rock contribution from a granitic terrain with subordinate contributions from metamorphic and/or metasedimentary rocks. Al_2O_3 and Cr enrichment in quartzites resulted from deposition of Al_2O_3-rich chromite grains derived from isolated exposures of ultramafic rocks. Possible K-metasomatism has also been inferred from the chemical composition of the quartzites. From field distributions, petrographic characteristics, chemical compositional data and inferred source rock contribution, it may be inferred that the conglomerate-quartzite association occurring in and around Tattekere and Kumkumna Hosuru villages in the Holenarsipur I Supracrustal Belt represents a single horizon with a near-basal position in the stratigraphic sequence. This suggests a basalear-basal I unconformity in the stratigraphic succession of Holenarsipur Supracrustal Belt.
机译：在印度卡纳塔克邦前寒武纪地质的重要方面，发生在霍特纳尔西布尔超硬带的Tattekere和Kumkumna Hosuru村庄及其周围的砾岩-石英岩岩石的起源和地层解释。由于有关其起源和地层状况的争论，以前的工作人员已经以不同的方式解释了霍纳西布尔超硬壳带的地质情况。在目前的工作中，已经尝试根据最近的观察和分析结果解决争议。砾岩和石英岩的岩石学特征，主要沉积结构的发生及其与北部地区已证实的沉积石英岩的相似性，以及石英岩的化学成分，都表明了这种沉积的成因。石英岩的重矿物和化学成分表明，花岗岩地带的主要源岩贡献，变质和/或变质沉积岩的次要贡献。石英岩中Al_2O_3和Cr的富集归因于超镁铁质岩石的单独暴露所致的富含Al_2O_3的铬铁矿颗粒的沉积。还可以从石英岩的化学组成中推断出可能的K-介晶作用。从田间分布，岩相特征，化学成分数据和推断的烃源岩贡献，可以推断出，Holenarsipur I Supracrustal带中Tattekere和Kumkumna Hosuru村庄及其周围发生的砾岩-石英岩结合代表了一个具有近基底的单一层位地层层序中的位置。这表明Holenarsipur上壳带的地层演替中存在基底/近基底I不整合面。

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