川圹高原中生代以来隆升-剥露过程的磷灰石裂变径迹热年代学制约及意义

The Lanping-Simao basin and Khorat basin both developed the potash salt deposition, which is located at the southeastern Tibetan Plateau and separated by the Xiangkhoang Plateau (extensively distributed the Paleozoic - early Mesozoic granite intrusion). The basically consistent salt mineral assemblage, element geochemical characteristics and magnetostratigraphy seems to indicate that there may be a unified basin during the Cretaceous, then was separated. However, the quantity of resource is disparity. Especially, there is no evidence to the uplift of the Xiangkhoang Plateau. Based on the mountain-basin coupling, a series of apatite fission track chronology sequence of the Xiangkhoang Plateau and the Mesozoic - Cenozoic Lanping-Simao and Khorat basins will be presented in this study. Combined with the paleo-currents, assemblage of the heavy mineral and zircon U-Pb age data, the detailed tectonic uplift - exhumation history of the Xiangkhoang Plateau since the Mesozoic will be built, which can provide the geomorphic constraints to the Cretaceous pan basin in the Lanping-Simao and Khorat regions. If the unity of the Cretaceous basin existed, the tectonic uplift - exhumation history equaled to the process of the disintegration and evolution of the uniform basin. That can not only help understand the tectonic deformation (extrusion) of the southeastern Tibetan Plateau, also provide the direction to research and exploration of the potash salt resource in the Yunnan province.

青藏高原东南缘的兰坪-思茅盆地与呵叻盆地现今被川圹高原（广泛发育古生代-早中生代花岗岩类侵入体）所分隔，两者均产出固体海相钾盐矿，且盐类矿物组合、元素地球化学特征及磁性地层年代基本一致，可能白垩纪成盐时期两者为统一的泛盆地，之后泛盆地解体。但两者资源量相差悬殊、缺乏分隔两者的川圹高原形成隆升的证据。本申请拟从盆山耦合角度，通过系列的川圹高原山体基岩及两侧中-新生代盆地沉积物的磷灰石裂变径迹热年代学研究，结合两侧盆地古水流、重矿物组合分析以及前人锆石U-Pb年龄资料，获取磷灰石裂变径迹、物源区和古水流变化信息，建立川圹高原中生代以来详细的构造隆升-剥露历史，为兰坪-思茅与呵叻盆地成钾盐时期是否存在泛盆地提供地貌约束。如果白垩纪存在统一盆地，则川圹高原的构造隆升-剥露历史就是统一盆地解体和演化过程。这对理解青藏高原东南缘构造变形（挤出）过程及云南钾盐资源的研究和勘探具有重要参考价值。

川圹高原中生代以来详细的构造隆升-剥露历史对云南思茅盆地与老挝-泰国的呵叻盆地在钾盐形成时期是否存在泛盆地及现今构造格局的形成过程有重要意义。然而，由于人文和地理因素限制，该区域的地质研究程度尚浅。为此，本项目选择川圹高原冯沙万地区花岗岩剖面和思茅盆地中-新生代地层分别开展磷灰石裂变径迹和锆石U-Pb热年代学研究。结合前人老挝万象盆地塔贡组和呵叻盆地马哈萨拉勘组锆石U-Pb年代学资料，根据锆石U-Pb年龄谱的变化特征，本项目认为思茅盆地与万象和呵叻盆地在中生代钾盐成藏时期为一个统一的泛盆地，沉积物经过思茅盆地进入越南北部进而进入呵叻盆地。而川圹高原中-新生代以来分别在68Ma、~52Ma和35Ma发生快速隆升事件，结合思茅盆地锆石U-Pb年龄组分在始新世中晚期（E2-3）发生改变，表明在68Ma时期川圹高原的初次隆升可能并未达到多大的高度，泛盆地仍然存在，而真正使泛盆地解体，阻断了物源通道的隆升是~52Ma的快速隆升事件。与此同时，基于本项目在高原东南部剑川盆地及高原东北部祁漫塔格山的裂变径迹热年代学研究表明，川圹高原35Ma的快速隆升事件是对区域岩浆作用及构造环境的响应。这对云南及我过中生代钾盐资源的研究和勘探具有重要参考价值，同时对于完善、深入理解和构建整个青藏高原的的构造变形过程提供了新的线索。