Tectonic evolution of the Central Andean Plateau and implications for ore distribution

中部安第斯高原的构造演化及其对矿石分布的影响

• 批准号: 576765-2022
• 负责人: Saylor, JoelJE
• 金额: $ 1.82万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Alliance Grants
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=751276
• 关键词: Tectonic; evolution; Central; Andean; Plateau

In the entirety of the Andes, the Central Andean Plateau (CAP) is anomalously wide, with distances between the subduction zone in the west and the easternmost deformation front up to 600-800 km. The CAP also hosts 70 km thick crust: the thickest in South America. The CAP has experienced vertical-axis rotations resulting in formation of the Bolivian orocline and greater shortening than regions to the north or south. The CAP also hosts copper, tin, and silver in Eocene (~45-35 million years ago) deposits ringing the CAP. Some of these deposits are among the largest in the world and therefore understanding the geodynamic processes that drove Eocene basin formation also provides insight into the processes that form large ore deposits.Multiple hypotheses, including both upper and lower plate effects, have been advanced to explain the evolution of the CAP and its anomalous characteristics. The large scale implicated by many of these mechanisms requires equally large-scale observations. However, testing these hypotheses has been hampered by a lack of datable material, particularly in Paleogene clastic strata. The lack of datable material has hampered stratigraphic correlations across the CAP, and therefore evaluation of the rate of subsidence (downward crustal movement) which accommodated sediment accumulation. The timing and rate of subsidence are symptomatic of specific geodynamic mechanisms acting to cause vertical crustal displacement. This proposal seeks funding to develop a preliminary correlation among Paleogene strata in Bolivia. We will use U-Pb geochronology of detrital zircons in Paleogene strata to develop independent chronostratigraphies at multiple latitudes in Bolivia. This will be interpreted and correlated in the context of newly acquired seismic lines across the Altiplano. This proposal will enable a new collaboration and research visits between PI Saylor and collaborator Ramos and their students.

在整个安第斯山脉中，安第斯高原中部（CAP）非常宽，西部的俯冲带和最东部的变形前缘之间的距离可达600-800 km。CAP还拥有70公里厚的地壳：南美洲最厚的地壳。CAP经历了垂直轴的旋转，导致玻利维亚的造山带的形成和更大的缩短比北部或南部地区。CAP还在环绕CAP的始新世（约4500 - 3500万年前）矿床中含有铜、锡和银。其中一些矿床是世界上最大的矿床之一，因此，了解驱动始新世盆地形成的地球动力学过程也提供了对形成大型矿床的过程的深入了解。多种假说，包括上板和下板效应，已被提出来解释CAP的演化及其异常特征。其中许多机制所涉及的大规模需要同样大规模的观察。然而，测试这些假设一直受到阻碍，缺乏可测年的材料，特别是在古近纪碎屑岩地层。缺乏可测年的材料阻碍了CAP的地层对比，因此也阻碍了对沉降速率（地壳向下运动）的评估，沉降速率可容纳沉积物的积累。沉降的时间和速率是引起地壳垂直位移的特定地球动力学机制的征兆。该提案旨在寻求资金，以便在玻利维亚的古近纪地层之间进行初步对比。我们将利用古近纪地层中碎屑锆石U-Pb年代学在玻利维亚多纬度地区建立独立的年代地层学。这将在新获得的横跨高原的地震线的背景下进行解释和相关。该提案将使PI Saylor和合作者拉莫斯及其学生之间的新合作和研究访问成为可能。