摘要:在准噶尔盆地东部火烧山地区中二叠统平地泉组的暗色泥岩中，发育4层特殊的含方沸石凝灰质豆粒灰岩。通过岩心观察、显微镜下薄片鉴定、电子探针分析方法，对该凝灰质豆粒灰岩的岩矿特征和成因机理进行了研究，得出豆粒主要有3类。第一类最常见，具有核心和同心层包壳，包壳有3～7层，按核心特点又可划分为6种，第1种豆粒核心含有特殊“环带结构”方沸石，其余5种核心含有近圆形—他形方沸石、黄铁矿、火山玻璃、方解石及凝灰质等。方沸石环带的电子探针分析结果为，内部成分偏酸性，外部偏基性；将其成分与近圆形及他形方沸石进行对比，具有明显低镁、富铁、高锶的特点，认为“环带结构”方沸石应是湖底岩浆热液喷流作用形成，他形方沸石为“热水”与“正常湖水”混合后胶体沉淀形成。因此第一类豆粒是在核心（方沸石、方解石或火山玻璃等）形成后，由于湖底喷流作用发生，湖水动荡，水动能发生变化而形成明暗相间圈层。第二类豆粒，具有单层薄包壳，核心由凝灰质、泥晶方解石和火山玻璃或生物碎屑组成，其形成与火山作用关系更密切。第三类豆粒由近等大的方解石圆球粒构成，形成与生物作用有关。含方沸石凝灰质豆粒灰岩的发现对准噶尔盆地东部中二叠统热水喷流沉积作用研究具有重要的意义。
关键词: 豆粒/
环带结构方沸石/
热水喷流作用/
平地泉组/
准噶尔盆地
Abstract:Four special layers of limestone characterized by analcime-bearing pisolite occurred in the black mudstone in Guadalupian Pingdiquan Formation in Huoshaoshan area of eastern Junggar Basin. The petrology, mineralogy, and forming mechanism are studied using a series of methods, including core observation, microscopic thin section analysis and electron microprobe analysis. Main observations and interpretations are as followed. There are three main types of pisolite. The first type is the most common one, with core and a typical band structure of concentric rings, which has 3~7 layers. It is subdivided into 6 types on the basis of the core characteristics. The first type contains analcime with zonal structure. The other five types contain subround to anhedral zeolite, pyrite, volcanic glass, calcite and tuff, etc. The results of electron microprobe analysis of analcime zoning show that the internal composition is acidic; while the external composition is basic. Comparing with that of near-round and allotriomorphic analcime, its composition is, obviously low in magnesium, rich in iron and high in strontium. The zonal structured analcime should be formed by the magmatic hydrothermal exhalation at the bottom of the lake. Besides, the anhedral analcime is formed from colloid precipitation by mixing "hydrothermal fluid" and "lake water". As a consequence, after the formation of the core(analcime, calcite or volcanic glass, etc.), the first type of pisolite form a bright and dark circle layer which are related to the hydrothermal exhalation at the lake bottom, the turbulence of lake water and the change of water kinetic energy. The second type has a single-layer thin outer shell, and the core is composed of tuff, micritic calcite and volcanic glass or biological fossil fragments, and its formation is more closely related to the volcanism; The third type of pisolite is composed of nearly the same size of calcite pellets, and its formation is related to biological processes. Generally speaking, the analcime-bearing tuffaceous pisolitic limestone play an important role to explore the hydrothermal exhalative activities widely distributed in the Guadalupian in the eastern Junggar Basin.
Key words:Pisolite/
"Zonal structure" analcime/
Hydrothermal exhalation/
Pingdiquan Formation/
Junggar Basin
PDF全文下载地址:
http://www.dzkx.org/data/article/export-pdf?id=e879f52f-4a77-435e-847d-b413900566df
