Evaporites are widely distributed within continental “red beds” in the Lanping–Simao Basin, west Yunnan, China. Sr (Strontium), S (Sulfur), and O (Oxygen) isotope compositions have been measured on 54 sulfate or/and sulfate-bearing samples collected from Lanping, Nuodeng, Jinggu, Mengyejing, Baozang throughout the Lanping–Simao Basin. The ⁸⁷Sr/⁸⁶Sr ratios of all samples (0.708081 to 0.710049) are higher than those of contemporaneous seawater, indicating a significant continental contribution to the drainage basin. Sulfates in the Lanping Basin have higher ⁸⁷Sr/⁸⁶Sr ratios (0.709406 to 0.710049) than those (0.708081 to 0.709548) in the Simao Basin. Nevertheless, the δ³⁴S values of gypsums (13.4‰ to 17.6‰) in Lanping and Baozang fall within the range of Cretaceous seawater. Gypsums from a single section in Baozang have trends of decreasing δ³⁴S values and increasing ⁸⁷Sr/⁸⁶Sr ratios from base to top, indicating continental input played an increasingly significant role with the evaporation of brines. High δ³⁴S values (20.5‰ to 20.7‰) of celestites in Lanping are probably caused by bacterial sulfate reduction (BSR) process in which ³⁴S were enriched in residual sulfates and/or recycling of Triassic evaporites. The reduced δ³⁴S values of gypsums (9.5‰ to 10.4‰) in Nuodeng could have been caused by oxidation of sulfides weathered from Jinding Pb-Zn deposit. The complex O isotope compositions indicate that sulfates in the Lanping–Simao Basin had undergone sulfate reduction, re-oxidation, reservoir effects, etc. In conclusion, the formation of continental evaporites was likely derived from seawater due to marine transgression during the Cretaceous period. Meanwhile, non-marine inflows have contributed to the basin significantly.

中文翻译：

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兰坪-思茅盆地蒸发岩的Sr，S和O同位素组成

蒸发物广泛分布在云南西部兰坪-思茅盆地的大陆“红层”内。在从兰坪-思茅盆地的兰坪，诺登，景谷，孟业井，宝藏采集的54个硫酸盐或/和含硫酸盐的样品中，测量了锶（锶），硫（硫）和氧（氧）同位素组成。所有样品（0.708081至0.710049）的⁸⁷ Sr / ⁸⁶ Sr比值均高于同期海水，表明该大陆对流域的贡献很大。兰坪盆地的硫酸盐比司茅盆地的硫酸盐具有更高的⁸⁷ Sr / ⁸⁶ Sr比（0.709406至0.710049）（0.708081至0.709548）。尽管如此，δ ³⁴兰坪和宝藏的石膏S值（13.4‰〜17.6‰）在白垩纪海水范围内。从在Baozang单个部分石膏具有降低δ趋势³⁴的价值观，增加⁸⁷ SR / ⁸⁶从基部Sr比值顶部，表示欧陆输入演奏与盐水的蒸发日益显著的作用。高Δ ^34个兰坪celestites可能是由硫酸盐还原细菌（BSR）过程中引起的，其中的价值观（20.5‰至20.7‰）³⁴小号富集在残余的硫酸盐和/或三叠纪蒸发岩回收。减小的δ ³⁴诺登地区的石膏S值（9.5‰至10.4‰）可能是由金顶铅锌矿床风化的硫化物氧化引起的。复杂的O同位素组成表明，兰坪—思茅盆地的硫酸盐经历了硫酸盐还原，再氧化，储层效应等作用。总之，由于白垩纪时期海侵，大陆蒸发物的形成很可能来自海水。同时，非海洋的涌入对该流域做出了重要贡献。