Ar-40/Ar-39 geochronology of supergene K-bearing sulfate minerals: Cenozoic continental weathering and its paleoclimatic significance in the Tu-Ha Basin, northwestern China
Ar-40/Ar-39 geochronology of supergene K-bearing sulfate minerals: Cenozoic continental weathering and its paleoclimatic significance in the Tu-Ha Basin, northwestern China
复制标题
表生含钾硫酸盐矿物Ar-40/Ar-39年代学：吐哈盆地新生代大陆风化及其古气候意义
DOI：
10.1016/j.palaeo.2016.01.005
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Yang Li
中科院分区：
文献类型：
--
作者：
Yang Jing;Zheng De-Wen;Chen Wen;Hough Brian;Qiu Hua-Ning;Wang Wei-Tao;Wu Ying;Yang Li
对吐哈盆地红山、六黄山和菜花沟矿床的三个风化剖面进行了表生黄钾铁矾和亚瓦派石的 40Ar/39Ar 增量加热分析。这些分析提供了风化和表生富集的时间和持续时间的数值限制。严格约束的高原年龄和最佳拟合的反等时线产生 40Ar/39Ar 年龄，范围从 33.3 ± 0.5 Ma 到 3.3 ± 0.4 Ma (1σ)。我们的 40Ar/39Ar 年龄，与已发表的年龄相结合，表明风化和表生富集的长期历史，并由此推断，有利于强烈化学风化的干旱半干旱气候（至少有中等量的降水（> 10 cm/y））出现在 33.3 Ma、27.7–23.3 Ma 和 16.4–14.7 Ma，并盛行于 11 至 14.7 Ma。 7.8 马。然后，从干旱半干旱向极度干旱条件和以极度干旱条件为主的逐渐变化可能至少持续了约 10 年。 3.3 马。风化年代学推断的气候含义与吐哈盆地连木沁剖面新生代沉积序列的化学参数和同位素组成一致，证明了40Ar/39Ar法风化年代学作为干旱区古气候指标的可靠性。我们的研究结果表明，副提斯海的退缩减少了西风向东向吐哈盆地的水汽输送，导致了渐新世的干旱化，而青藏高原和天山山脉隆起导致的雨影效应增加，在吐哈盆地晚中新世以来的干旱化历史中发挥了重要作用。
40Ar/39Ar incremental-heating analyses of supergene jarosite and yavapaiite were conducted for three weathering profiles at the Hongshan, Liuhuangshan, and Caihuagou deposits in the Tu–Ha Basin. The analyses provide numerical constraints on the timing and duration of weathering and supergene enrichment. Well-constrained plateau ages and best-fitting inverse isochrons yield40Ar/39Ar ages ranging from 33.3 ± 0.5 Ma to 3.3 ± 0.4 Ma (1σ). Our40Ar/39Ar ages, combined with the published ages, indicate that a protracted history of weathering and supergene enrichment and, by inference, arid–semiarid climate (with at least a moderate amount of precipitation (> 10 cm/y)) favorable to intense chemical weathering emerged at 33.3 Ma, 27.7–23.3 Ma, and 16.4–14.7 Ma, and prevailed from 11 to 7.8 Ma. Then, a progressive change from arid–semiarid toward hyperarid conditions and predominantly hyperarid conditions may have persisted since at least ca. 3.3 Ma. The climatic implications inferred from the weathering geochronology are in agreement with the chemical parameters and isotopic compositions of the Cenozoic sedimentary sequence from the Lianmuqin section in the Tu–Ha Basin, attesting to the reliability of weathering geochronology by the40Ar/39Ar method as an indicator of paleoclimate in arid areas. Our results suggest that the retreat of the Paratethys Sea, which would have reduced eastward water vapor transport by the westerlies to the Tu–Ha Basin, led to its aridification in the Oligocene and that increased rain shadow effects, resulting from uplift of the Tibetan Plateau and Tian Shan Mountains, played important roles in the aridification history of the Tu–Ha Basin since the late Miocene.