The eastern Junggar Basin, controlled by continental extension (rift), was deposited by lacustrine dominated sediments during middle Permian Lucaogou period. An unusual porphyritic-like texture was observed in Lucaogou/Pingdiquan dark fine-grained organic-rich sediments in two sub-tectonic units in the basin. The “phenocrysts” are composed of two types of mineral assemblages. The first is a coarse euhedral calcite assemblage in the Jimusar Sag, and the second consists of dolomite, analcime, and pyrite in the Shishugou Sag. The lithological and mineralogical features indicate a hydrothermal origin for these phenocryst-like minerals. The chondrite-normalized rare earth element patterns show flat or positive Ce anomalies and negative Eu anomalies, which reflect a suboxic to anoxic, off-axis site from the center of the fault system, where the temperature of the hydrothermal fluid might be less than 250 °C. The high ratios of Ba N /La N at 1.6–65.5, strongly positive Sr anomalies at Sr/Sr* = 5.54–39.9, and relatively low 87 Sr/ 86 Sr isotopes at 0.705002–0.705776 in the coarse calcite suggest an origin of mixed sources of lake water, underlying biogenetic sediments, and deep magmatic water. However, the low 87 Sr/ 86 Sr ratios of 0.705321–0.705968 in the dolomite and δ 34 S V-CDT of 10.8‰–12.3‰ in the pyrite indicate that water–underlying-rock interaction and the abiotic thermochemical sulfate reduction of lake water or organic matter might have participated together resulting in the precipitation of the dolomite–analcime–pyrite assemblages in the Shishugou Sag.

中文翻译：

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准噶尔盆地东部二叠系湖相芦草沟泥岩中方解石和白云石-方解石-黄铁矿热液矿物组合

准噶尔盆地东部受大陆伸展（裂谷）控制，沉积于中二叠世芦草沟期以湖相为主的沉积物。在盆地内两个亚构造单元的芦草沟/平地泉暗细粒富有机质沉积物中观察到异常的似斑状结构。“斑晶”由两种矿物组合组成。第一个是吉木萨尔凹陷的粗自形方解石组合，第二个是石树沟凹陷的白云石、方沸石和黄铁矿。岩性和矿物学特征表明这些斑晶状矿物的热液成因。球粒陨石归一化的稀土元素模式显示出平坦或正的 Ce 异常和负的 Eu 异常，这反映了从断层系统中心的低氧到缺氧的轴外位置，其中热液的温度可能低于 250 °C。Ba N / La N 的高比率为 1.6-65.5，Sr/Sr* = 5.54-39.9 处的 Sr 异常正异常，以及在粗方解石中 0.705002-0.705776 处相对较低的 87 Sr/86 Sr 同位素表明混合的起源湖水、下伏生物成因沉积物和深层岩浆水的来源。然而，白云岩中 0.705321–0.705968 的低 87 Sr/86 Sr 比率和黄铁矿中 10.8‰–12.3‰ 的 δ 34 S V-CDT 表明水-下伏-岩石相互作用和非生物热化学硫酸盐还原湖水或有机质可能共同参与导致石树沟凹陷白云石-方沸石-黄铁矿组合的沉淀。Sr/Sr* = 5.54-39.9 处的 Sr 强正异常和粗方解石中 0.705002-0.705776 处的 87 Sr/86 Sr 同位素相对较低，表明湖水、下伏生物成因沉积物和深层岩浆水的混合来源。然而，白云岩中 0.705321–0.705968 的低 87 Sr/86 Sr 比率和黄铁矿中 10.8‰–12.3‰ 的 δ 34 S V-CDT 表明水-下伏-岩石相互作用和非生物热化学硫酸盐还原湖水或有机质可能共同参与导致石树沟凹陷白云石-方沸石-黄铁矿组合的沉淀。Sr/Sr* = 5.54-39.9 处的 Sr 强正异常和粗方解石中 0.705002-0.705776 处的 87 Sr/86 Sr 同位素相对较低，表明湖水、下伏生物成因沉积物和深层岩浆水的混合来源。然而，白云岩中 0.705321–0.705968 的低 87 Sr/86 Sr 比率和黄铁矿中 10.8‰–12.3‰ 的 δ 34 S V-CDT 表明水-下伏-岩石相互作用和非生物热化学硫酸盐还原湖水或有机质可能共同参与导致石树沟凹陷白云石-方沸石-黄铁矿组合的沉淀。