Characteristics of the paleosol at the Archean - Proterozoic contact in the Aravalli Craton, NW India and paleoclimatic implications

西北印度克拉通的太古宙-元古宙接触（APC）被几处富含白色云母的岩性所点缀，这些岩性在当地的小坑中被采掘。这些富铝岩性（随后变质），被描述为在太古宙花岗岩基底上发育的“古土壤”，提供了一个理想的环境来推断大气条件，因为它们是在大气-岩石圈界面形成的。前人根据地质和地球化学标准，提出了APC古土壤是在缺氧条件下形成的。这样的解释需要根据我们在图尔西-纳姆拉剖面上部发现的富铁层来重新评估。这些古土壤形成于2.5 - 2.1 Ga之间，这是一个有趣的大气条件变化的时间间隔，我们的研究将提供迄今为止没有尝试过的关于印度太古代克拉通的信息。在本提案中，我们申请资助进行实地研究和高精度的地球化学和矿物化学数据，以推断古风化条件。这些发现将与在南非、加拿大和澳大利亚得到充分研究的太古宙地体的类似环境进行比较。

The Archean – Proterozoic contact (APC) in the NW Indian craton is punctuated by several occurrences of white mica-rich lithologies, which are locally quarried in small pits. These Al-rich lithologies (subsequently metamorphosed), described as ‘paleosols’ developed over an Archean granitic basement, offer an ideal setting to deduce ambient atmospheric conditions as they are formed at the atmosphere-lithosphere interface. Previous studies have proposed formation of APC paleosols under oxygen-deficient conditions on the basis of geological and geochemical criteria. Such an interpretation needs to be reassessed in the light of our discovery of an iron-rich horizon from upper part of the Tulsi-Namla section. These paleosols were formed between 2.5 and 2.1 Ga, the interesting time interval of changing atmospheric conditions and our study would provide information not attempted so far from Archean cratons in India. In this proposal we apply for funding for a field study and for high precision geochemical and mineral-chemical data to deduce the paleoweathering conditions. The findings will be compared with similar settings from well-studied Archean terranes in South Africa, Canada and Australia.