碳酸盐岩等体积风化的过程及机制研究

灰岩及白云岩等碳酸盐岩约占地球大陆表层岩性组成的10.4%，其主要由易于溶解的碳酸盐矿物构成。但越来越多的野外证据表明，碳酸盐岩可以发生等体积风化，其风化产物（红色石灰土）可以保留母岩的结构、构造和体积。因此，碳酸盐岩风化过程要比传统的认识更为复杂，而溶蚀-残余机制并不能解释其所有的风化过程。目前，对于碳酸盐岩等体积风化及红色石灰土形成的过程、机制和风化条件尚不清楚。本项工作拟以碳酸盐岩广泛分布的云贵高原为调查区域，以碳酸盐岩-红色石灰土等体积风化体系为研究对象，基于对碳酸盐岩母岩-碳酸盐岩腐岩-红色石灰土风化序列的研究，揭示岩（土）体物理性质、矿物和化学组成的演化过程；了解风化产物中Si、Al、Fe等组分的来源、迁移方式及其富集过程；初步阐明碳酸盐岩等体积风化的过程、机制及其发育的特殊风化条件。该工作对于岩溶地貌演化、岩溶型铝土矿成因、石漠化及岩溶地质灾害防治等方面的研究亦具有重要意义。

Carbonate rocks (limestone, dolostone etc.) account for 10.4% of the entire lithologic composition of the Earth’s continental surfaces. Carbonate rocks are mostly composed of easily dissolved carbonate minerals. In addition to dissolution-residue weathering, however, there is increasing field evidence that carbonate rocks could possess the isovolumetric weathering. In other words, the weathering products (terra rossa) of carbonate rocks can retain substantially the texture, structure and volume of the parent rocks, despite extensive losing of soluble materials. Hence, the weathering processes of carbonate rocks are more complicated than conventionally recognized, while the dissolution-residue mechanism cannot explain the weathering processes of all carbonate rocks. In fact, the processes, mechanisms and weathering regimes of isovolumetric weathering in the carbonate rocks are uncertain, and the origin of terra rossa overlying carbonate rocks remains controversial..In this project, we will make the Yunnan-Guizhou Plateau, where dominated by the carbonate rocks, as the focus of the investigation. The isovolumetric weathering of carbonate rocks in area will be the key research object. The weathering sequence of the carbonate rocks--the regolith of carbonate rocks--the terra rossa and related deposits will be examined. Based on all of the analytical data for physical features, mineral compositions, geochemical compositions and 143Nd/144Nd, δ30Si, δ56Fe isotopic tracing indices, we will (i) reveal the evolutionary processes of physical features, (ii) identify the evolutionary processes of mineral and geochemical compositions, (iii) investigate the provenance, input mode and enrichment processes of Si、Al、Fe, etc. in the weathering products (terra rossa etc.), and (iv) clarify the processes and mechanisms of isovolumetric weathering in the carbonate rocks. Furthermore, the specific weathering regime for the isovolumetric weathering of carbonate rocks will be explored based on comprehensive investigation for the geomorphological, geological and hydrogeological settings. This study could shed light on the genesis of karst landscapes, the origins of karst bauxite, the prevention of rocky desertification and geological disasters in the karst terrains.