Thermal Alteration History of the Fenghuoshan Group, Hoh Xil Basin, Northern Tibetan Plateau: Insights From Clumped Isotope Thermometry
Thermal Alteration History of the Fenghuoshan Group, Hoh Xil Basin, Northern Tibetan Plateau: Insights From Clumped Isotope Thermometry
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DOI：
10.1029/2021jb022009
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发表时间：
2021-10-01
影响因子：
3.9
通讯作者：
Wei, Gangjian
中科院分区：
文献类型：
--
作者：
Kong, Kai;Deng, Wenfeng;Wei, Gangjian
碳酸盐凝块同位素（Delta（47））温度计已广泛应用于沉积盆地的古气候和古高程重建。它的可靠使用要求碳酸盐不受后期成岩蚀变的影响，并保留其沉积三角洲（47）成分，而在盆地的埋藏史中并非总是如此。因此，确定埋藏过程中发生的蚀变机制对于正确解释Delta（47）特征至关重要。本文利用Delta（47）温度计研究了青藏高原北方可可西里盆地风火山群埋藏过程中可能的碳酸盐蚀变。FHSG厚度接近4.5 km的30个碳酸盐样本的Delta（47）温度[T（Delta（47））]范围为51至132摄氏度，超过了表面温度，这意味着热蚀变对FHSG碳酸盐的影响。T（Delta（47））值结合水岩交换模型，表明蚀变发生在低水岩比的封闭埋藏条件下。固态重排序模型无法预测Delta（47）值，即使使用修改的时间-温度历史。相比之下，大多数测量的Delta（47）值与再结晶模型的预测一致。因此，提出的蚀变方案是FHSG碳酸盐在深埋和随后的折返过程中经历了渐进的微尺度重结晶，在此过程中，重结晶碳酸盐与环境埋藏温度平衡，因此修改了Delta（47）值。这项研究突出了三角洲（47）测温和相关模型的潜力，用于评估沉积盆地中碳酸盐岩的埋藏史和成岩作用。
The carbonate clumped isotope (Delta(47)) thermometer has been widely used for paleoclimatic and paleo-elevation reconstructions in sedimentary basins. Its reliable use requires that carbonates are free from later diagenetic alteration and retain their depositional Delta(47) compositions, which is not always the case during the burial history of a basin. Therefore, identifying the alteration mechanisms that occurred during burial is essential for the correct interpretation of Delta(47) signatures. In this study, we used the Delta(47) thermometer to investigate possible carbonate alteration during burial of the Fenghuoshan Group (FHSG) in the Hoh Xil Basin, northern Tibetan Plateau, China. The Delta(47) temperatures [T(Delta(47))] of 30 carbonate samples through the similar to 4.5 km thickness of the FHSG range from 51 to 132 degrees C and exceed the surface temperature, implying the effects of thermal alteration on FHSG carbonates. The T(Delta(47)) values combined with the water-rock exchange model, indicating that the alteration occurred under closed burial conditions at low water:rock ratios. The solid-state reordering model fails to predict the Delta(47) values, even with a modified time-temperature history. In contrast, most measured Delta(47) values are in agreement with predictions from recrystallization models. Therefore, the proposed alteration scenario is that FHSG carbonates underwent progressive microscale recrystallization during deep burial and subsequent exhumation, during which process recrystallized carbonate equilibrated with ambient burial temperature and therefore modified Delta(47) values. This study highlights the potential of Delta(47) thermometry and related models for evaluating the burial history and diagenesis of carbonates in sedimentary basins.