黔中隆起金沙地区中新生代隆升剥蚀的裂变径迹分析

对贵州金沙地区取样进行了裂变径迹热史模拟,结合地质分析再现了黔中隆起的沉降和隆升剥蚀作用过程。该地区经历了180～70Ma时期的沉降埋藏增温和70Ma之后的剥蚀冷却降温两大阶段。沉降阶段的增温速率为0.909℃/Ma,对应的T3—K的沉积厚度约为4550m。冷却降温曲线分为三段:70～15Ma,样品温度从120℃降低到60℃,冷却速率为1.09℃/Ma;15～5Ma为一个"平台"期,样品温度维持在60℃左右;5Ma至今,样品温度从60℃快速冷却至20℃,冷却速率达8℃/Ma,这与喜马拉雅期云贵高原的整体隆升和晚期快速崛起相对应。计算表明,晚白垩世以来的隆升剥蚀量达2800m左右。

Fission Track Analysis of Meso-Cenozoic Uplift and Denudation in Jinsha Area, the Qianzhong Uplift

A thermal history was modeled by fission track dating in Jinsha area of Guizhou Province. Combined with geologic analysis, the subsidence, uplift and denudation processes of the Qianzhong Uplift are restored. This uplift has experienced 2 stages of processes: a) subsidence, burial and temperature rise from 180Ma to70 Ma; b) denudation and temperature decrease from 70 Ma till now. During the subsidence stage, the rate of temperature increase was 0.909℃/Ma and the corresponding sedimentary thickness of T3-K was about 4550m. during the de- nudation and temperature decrease, the curves of temperature decrease show three parts: a) from 70 to 15 Ma, sample temperature decreases from 120 to 60 ℃ by the rate of 1.09 ℃/Ma; b) from 15 to 5 Ma, it has a smooth stage and sample temperature keeps at 60 ℃; c) from 5 Ma till now, sample temperature decreases quickly from 60 to 20 ℃ by 8 ℃/Ma, which corresponds to Himalayan uplifts of the Yunnan and Guizhou Plateau. Calculation shows that the thickness of uplift and denudation has been about 2800m since Late Cretaceous period.