准噶尔盆地东部中二叠统平地泉组具“斑状”结构热水喷流沉积岩的成因及地质意义

发布时间：2018-04-30 06:53

  本文选题：“斑晶”白云石 + 方沸石　； 参考：《古地理学报》2017年02期

【摘要】：准噶尔盆地东部中二叠统平地泉组(相当于芦草沟组)发育一套陆内裂谷背景下的湖泊相砂岩、泥岩、灰岩、白云岩、凝灰岩互层以及它们的过渡岩石,是区内最主要的烃源岩和储集层。近年来,在帐北断褶带、石树沟凹陷和吉木萨尔凹陷中二叠统平地泉组暗色泥岩、泥晶白云岩中发现了一类特殊的沉积岩,该类岩石发育类似火山岩的斑状结构。"斑晶"主要为粗晶白云石、方解石、黄铁矿及方沸石等,在岩心标本上呈"树枝状"或"雪花状"散布于基质中;基质则主要由泥晶白云石或泥质沉积物构成,富含有机质,发育水平层理及小型变形层理等。岩石学和矿物学分析表明,"斑晶"往往为粗晶方解石或白云石的集合体,也常见黄铁矿、方沸石与碳酸盐矿物共生,"斑晶"方解石发育环带,而白云石未见明显环带。电子探针分析表明"斑晶"方解石具有低镁、低铁及锶分布不均匀的特点,而"斑晶"白云石(FeO含量介于7.272%~11.086%之间)与"基质"泥晶白云石(FeO含量为1.027%)相比具有明显富铁的特点。流体包裹体分析表明"斑晶"方解石均一温度平均为180.68℃,"斑晶"白云石均一温度平均为320.95℃。这种特殊"斑状"白云岩和"斑状"泥质岩很可能是湖底热液喷流作用的结果。当湖水沿深大断裂下渗至地下深处,与围岩发生物质交换并被加热后再沿断裂返回地表喷涌而出,热液流体携带的离子达到过饱和后就会析出方解石、白云石及黄铁矿等集合体,随热液的喷涌作用上升并破碎散落于湖底细粒沉积物内。"斑状"白云岩的发现对新疆北部中二叠统热水喷流沉积作用及该区油气的成因研究具有重要的意义。
[Abstract]:A set of lacustrine sandstone, mudstone, limestone, dolomite, tuff interbeds and their transitional rocks are developed in the eastern part of Junggar Basin, the Middle Permian Pingdiquan formation (equivalent to the Lucaogou formation), and a set of lacustrine sandstone, mudstone, limestone, dolomite, tuff interbeds and their transitional rocks. Is the most important source rock and reservoir in the region. In recent years, a special type of sedimentary rocks have been found in the Middle-Permian Pingdiquan formation dark mudstone and mud-crystal dolomite in the Shanbei fault fold belt, Shishugou sag and Jimusar sag. The porphyry structure of this kind of rock is similar to that of volcanic rock. " The porphyry "is mainly composed of coarse dolomite, calcite, pyrite and alpinite, which are distributed in the matrix in the form of" dendritic "or" snowflake "on the core specimens, while the matrix is mainly composed of mudded dolomite or muddy sediments, which is rich in organic matter. Horizontal bedding and small deformation bedding. The petrological and mineralogical analysis shows that "porphyry" is often an aggregate of coarse-grained calcite or dolomite, pyrite is common, andalcite is symbiotic with carbonate minerals, porphyry calcite develops a ring zone, but dolomite does not. The electron probe analysis shows that the "porphyritic" calcite has the characteristics of low magnesium, low iron and uneven distribution of strontium, while the content of Feo in the "porphyry" dolomite is between 7.2722 and 11.086%) and that in the "matrix" mudstone dolomite is 1.027%). The analysis of fluid inclusions shows that the average homogenization temperature of "porphyry" calcite is 180.68 鈩，

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