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Geochemical Characteristics of Quartzite in Parts of Paleoproterozoic Dhanjori Group, Singhbhum Craton, Eastern India: Implications for Provenance and Paleoweathering
Journal of the Geological Society of India ( IF 1.2 ) Pub Date : 2021-03-09 , DOI: 10.1007/s12594-021-1683-5
Usman Aarif Chaudhary , Shabber Habib Alvi

Singhbhum craton preserves the records of sedimentation, magmatism, and tectono-thermal events from Mesoarchaean to Neoproterozoic. The Dhanjori Group (DG), located on the northeast margin of the Singhbhum craton, comprises of a variety of rocks including quartz pebble conglomerate, quartzite, schist, inter-layered with mafic to intermediate and rarely acidic lava flows, tuff and agglomerate. Petrography and geochemical characteristics of the Dhanjori quartzite have been undertaken to interpret paleoweathering and provenance characteristics. Studied quartzites are made up of abundant quartz, feldspar, mica, and lithic fragments. With the help of geochemical data, the studied quartzites are classified as quartz-arenites and sub-arkoses. In addition to the A-CN-K plot, various chemical indices such as the chemical index of weathering (CIW), chemical index of alteration (CIA), and plagioclase index of alteration (PIA) indicate moderate to intense chemical weathering of the provenance under semi-humid climatic conditions. Rare earth element (REE) chondrite normalized patterns of the studied samples illustrate enriched light rare earth elements (LREEs) (LaN/SmN = 3.11–6.19), depleted heavy rare earth elements (HREEs) (GdN/YbN = 0.35–3.12) and negative Eu anomaly (Eu/Eu* = 0.55–0.87, ∼ 0.68). Such patterns are similar to that of the upper continental crust (UCC). In the discrimination function diagram, studied samples of the Dhanjori Group fall in quartzose sedimentary field. In addition, La/Sc vs. Th/Co and La-Th-Sc diagrams, various ratios like Th/Sc (∼0.61), La/Sc (∼4.42), Th/Co (∼0.03), La/Co (∼0.11), and Cr/Th (∼141.62) imply a mixed provenance for the studied samples. Hence, it has been inferred that the meta-sediments and ortho-amphibolites of the older metamorphic group, Singhbhum granitoid complex, as well as associated Archaean metavolcanic suites, would have acted as the probable source rocks for the studied Dhanjori quartzites.



中文翻译:

印度东部Singhbhum Craton古元古代Dhanjori组部分地区石英岩的地球化学特征:物源和古风化的意义

Singhbhum克拉通保留了从中古生界到新元古代的沉积,岩浆作用和构造热事件的记录。Dhanjori Group(DG)位于Singhbhum克拉通的东北边缘,由各种岩石组成,包括石英卵石砾岩,石英岩,片岩,中间夹有镁铁质至中度和极少酸性的熔岩流,凝灰岩和团聚体。Dhanjori石英岩的岩石学和地球化学特征已经被用来解释古风化和物源特征。研究的石英岩由丰富的石英,长石,云母和石屑碎片组成。借助地球化学数据,将研究的石英岩分类为石英亚砷酸盐和亚黑石。除了A-CN-K图外,还包括各种化学指数,例如耐候性化学指数(CIW),化学变化指数(CIA)和斜生胶酶变化指数(PIA)表示在半湿润气候条件下该种源的化学至中等至强烈化学风化。研究样品的稀土元素球粒晶归一化图案说明了富集的轻稀土元素(LREEs)(LaN / Sm N = 3.11–6.19),耗尽的重稀土元素(HREE)(Gd N / Yb N= 0.35-3.12)和负Eu异常(Eu / Eu * = 0.55-0.87,〜0.68)。这种模式类似于上大陆壳(UCC)。在判别函数图中,Dhanjori组的研究样本落在石英糖沉积场中。此外,La / Sc与Th / Co和La-Th-Sc图,各种比率如Th / Sc(〜0.61),La / Sc(〜4.42),Th / Co(〜0.03),La / Co( 〜0.11)和Cr / Th(〜141.62)表示研究样品的混合来源。因此,可以推断出,较老的变质族Singhbhum花岗岩类群的变质沉积物和邻闪石,以及相关的古生变火山岩套件,可能成为了所研究的Dhanjori石英岩的可能烃源岩。

更新日期:2021-03-09
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