缅甸沙林凹陷晚白垩世凝灰岩LA-ICP-MS锆石U-Pb年龄与地质意义

    U-PB AGES OF LA-ICP-MS ZIRCON FROM LATE CRETACEOUS TUFF IN THE SALIN DEPRESSION OF MYANMAR AND THEIR GEOLOGICAL SIGNIFICANCE

    • 摘要: 在沉积盆地沉积序列中,凝灰岩是源区火山活动与造山运动的直接产物,常见于在板块边缘。对缅甸中北部弧前盆地沙林凹陷内凝灰岩地层进行准确的年代学测量,探讨其形成的大地构造背景。研究认为, 对凝灰岩中锆石的年代学测量,得到的年龄分别为70±1.0 Ma,64.2±1.2 Ma,65±1.0 Ma,64±0.8 Ma,判断庞吉组沉积年代属于晚白垩世—早古新世;新特提斯洋的B型俯冲导致缅甸中央盆地的岩浆活动,在沙林凹陷内沉积了凝灰岩。

       

      Abstract: Tuff, as a direct product of volcanic activity, is often found along the edge of the plate. Accurate geochronological dating for the tuff formations in the Salin Depression of the pre-Arc Basin in the north-central part of Myanmar may found a reliable basis for stratigraphic division and calibration of the study area. The tectonic movement between blocks, supplemented by geochemical data, may provide time constraints for delineations of tectonic settings. Our data suggest that: 1) The ages of zircons in tuffs are 70±1.0 Ma, 64.2±1.2 Ma, 65±1.0 Ma, and 64±0.8 Ma., indicating that the Pangji Formation is Late Cretaceous in age. 2) The B-type subduction of the Neo-Tethys Ocean led to magmatic activity in the Central Basin of Myanmar. Tuff deposits derived are deposited in the Salin Depression.

       

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