Evidence of Extremely Light Gypsum from the Permian-Triassic (P/T) Event Boundary at the Meishan Section of South China
Evidence of Extremely Light Gypsum from the Permian-Triassic (P/T) Event Boundary at the Meishan Section of South China
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发表时间：
2004
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通讯作者：
Liang Handong
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作者：
Liang Handong
浙江长兴梅山剖面二叠系-三叠系（P/T）事件界线上存在著名的“白色粘土”和“黑色粘土”，本文采用同位素质谱技术，结合SF6标准制备方法，对两个界线粘土中天然捕获的石膏进行了硫组分的测定。令人惊讶的是，石膏具有非常负的δ值，包括-9.2（δ 34 S V CDT）或-4.6‰白色粘土中自形晶石膏的δ 33 SV CDT平均值为-10.7‰或-5.5‰，黑色粘土中的浸出水为-15.6‰或-8.2‰。据我们所知，这种极轻的硫为主的石膏，现在提供了最负的硫酸盐的硫同位素比值异常的P/T事件边界在梅山剖面，不仅是在本研究中发现的P/T剖面，而且在世界上其他大规模灭绝相关的边界剖面。这一发现将为了解P/T灾难性事件及其在地球过去的环境变化打开一个新的窗口。此外，靠近白色粘土的天然Fe S块体也被确定为通常的同位素组成，其平均值为+1.3‰（δ 34 SV CDT）和+0.7‰（δ 33 SV CDT），并且在我们的努力中未能证实任何预期的有机成因黄铁矿及其类似物的痕迹，这两者都可能排除了我们所发现的轻石膏的有机成因的可能性。因此，这种意想不到的石膏的起源仍有待于将来了解。
There are famous "white clay" and "black clay" existing in the Permian Triassic (P/T) event boundary at the Meishan section that is located in Changxing County, Zhejiang Province of South China.This study focuses on detecting sulfur composition of the gypsum naturally trapped in both of the boundary clays, by isotopic mass spectrometry assistant with standard method of SF 6 preparation. To our surprise, the gypsum proves to have extraordinarily negative delta values, including -9.2‰ (δ 34 S V CDT ) or -4.6‰ (δ 33 S V CDT ) in average for the gypsum in euhedral crystal selected form the white clay, -10.7‰ or -5.5‰ for the whole gypsum water extracted from the same clay, and -15.6‰ or -8.2‰ for those water extracted from the black clay. To our know ledge, such extremely light sulfur dominated gypsum, which now offers the most negative anomaly of sulfur isotope ratio of sulfate towards the P/T event boundary at Meishan section, is originally recognized in this study, not only for the P/T sections but also for other mass extinction related boundary sections in the world. This finding would open a new window for insight into the P/T catastrophic event as well as its subsequent changes of environment in the past of the Earth. Furthermore, native Fe S nuggets close to the white clay are also determined to be usual isotopic composition in average values of +1.3‰ (δ 34 S V CDT ) and +0.7‰ ( δ 33 S V CDT ),and any trace of expecting organic genetic pyrites as well as their analogs fails to prove in our efforts, both of which probably excludes a possibility of organic genesis for the light gypsum we find. Thus, origin of this unexpected gypsum remains to be understood in future.