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

印度克拉通西北部的太古代-元古代接触带（APC）被几处富含白色云母的岩性所打断，这些岩性是在当地的小矿坑中开采的。这些富含铝的岩性（随后变质），被描述为“古土壤”的太古代花岗岩基底上开发，提供了一个理想的设置来推断周围的大气条件，因为它们形成在大气-岩石圈界面。以往的研究提出APC古土壤的形成是在缺氧条件下的地质和地球化学标准的基础上。根据我们在Tulsi-Namla剖面上部发现的富铁层位，需要重新评估这种解释。这些古土壤形成于2.5和2.1 Ga之间，这是一个有趣的大气条件变化的时间间隔，我们的研究将提供印度太古代古土壤迄今为止尚未尝试的信息。在这个建议中，我们申请资助的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。这些发现将与南非、加拿大和澳大利亚经过充分研究的太古代化石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.