Neotectonics, structural geology, exhumation, zircon U-Pb, K-feldspar Ar-step-heating, apatite fission-track, U/Th-He apatite-zircon thermochronology, thermal and kinematic modeling

点击翻译按钮获取中文摘要

Uplift of the Central Andes as a topographic barrier to atmospheric circulation is an important parameter for climate models. Current debate centers an temporal and spatial differences in the growth pattern of the Puna (Argentina) and structurally distinct Altiplano (Bolivia) plateau. We address this problem by proposing a more rigorous study of the cooling and uplift, and kinematic history of the Puna using zircon U-Pb, K-feldspar Ar-step-heating, apatite fission-track, and apatite and zircon U/Th-He analyses and structural Field studies of fault-bound igneous intrusions at the Puna-Eastern Cordillera transition. We focus on 10 selected plutons in 2 key regions: (1) the northern Puna rim (Humahuaca, Tres Cruces region), and (2) the southern Puna rim (Sierra de Quilmes, Co. Chuscha). The higher closure temperatures of zircon U-Pb, K-feldspar Ar-step-heating and zircon U/Th-He allow to reconstruct the older, pre-Neogene thermal evolution and geothermal gradients, which is essential as it provides the structural and thermal conditions for subsequent Neogene plateau growth. The lower closure temperatures of apatite fission-track and apatite U/Th-He help to constrain the neotectonic history leading to exhumation. The resulting spatial and temporal differences in the cooling history of the igneous ranges allow to reconstruct growth patterns across the plateau, and structural analyses provide geometric constraints an contractional reverse-fault patterns and uplift architecture. The thermochronologic ages along the vertical elevation transects enables us to reconstruct the timing and rates of exhumation, indicating the age of onset of topographic barriers and increasing aridity at the lee-side of these barriers. Comparison of the results from the Puna with the Altiplano and other orogenic plateaus will provide a better understanding of how and how fast orogenic plateaus develop, and how they induce climate change.