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自六十年代初,在滇东地区上二叠统宣威组煤层中发现单矿物(高岭土)夹矸(现今国际上统称为“Tonsteins”夹层)以来,利用其固有的岩石学特性和良好的稳定性,在地质勘探和采矿生产中,对解决煤层对比和一系列地质问题,显示出明显的效果,现已初步查明它们的层位、分布、岩石类型、矿物组分、化学成分及某些微量元素特征。对部分层位的 Tonsteins 标本进行 X 光衍射和分离出来的付矿物进行扫描电镜签定,发现其中存在若干种高温矿物的完美晶体,主要有β—石英、磷灰石、锆英石、独居石以及已高岭石化的长石假晶。与国外类似岩石进行比较,认为这些 Tonsteins 系酸性火山灰沉积于泥炭沼中,经酸性介质分解蚀变为高岭石凝胶,并在成岩过程中转变而成。与滇东相邻的黔西,在该含煤岩系中 Tonsteins 的层数最多可达60层,看来,这只能是保存下来的一部分火山活动的“遗迹”;因此,可以推测在晚二叠世龙潭期,川滇古陆上的火山喷发相当活跃,时断时续,它与其东部沉积区的振荡运动——造成海水的进退和含煤岩系的旋回结构——遥相呼应。火山活动既为川滇古陆以东的广大沉积区提供了物质来源,又为成煤植物的生长提供了丰富的养料,在其它条件协调一致的配合下,促成了滇东——黔西这一片晚二叠世煤田的形成。
Since the early 1960s, single mineral (kaolinite) gangue (now collectively referred to as “Tonsteins” sandwich) has been found in the coal seams of the Xuanwei Formation in the Upper Permian of eastern Yunnan since its inherent petrological characteristics and good Stability in geological exploration and mining production, to solve the coal seam contrast and a series of geological problems, showing obvious results, has been initially identified their horizon, distribution, rock type, mineral composition, chemical composition and a Some trace elements characteristics. X-ray diffraction and separation of some of the deposited Tonsteins specimens were carried out by scanning electron microscopy and found that there were several perfect crystals of high-temperature minerals, including β-quartz, apatite, zircon, monazite As well as kaolinite feldspar fake crystal. Compared with similar foreign rocks, these Tonsteins are believed to be acidic volcanic ash deposited in peat bogs, altered to kaolinite by acidic media, and transformed during diagenesis. Tonsteins in the coal-bearing series, up to 60 levels in Qianxi, adjacent to eastern Yunnan, appear to be only “relics” of preserved volcanic activity; therefore, it can be assumed that at night During the Longtan period of the Permian, volcanic eruptions on the Sichuan-Yunnan ancient land were quite active and intermittent, which echoes the oscillation movement in the sedimentary area of the east China, causing the advance and retreat of the seawater and the swirling structure of the coal-bearing rocks. The volcanic activity not only provided the material source for the vast sedimentary area to the east of Sichuan-Yunnan Plateau, but also provided the abundant nourishment for the growth of coal-forming plants. Under the co-ordination of other conditions, it contributed to the late-east Yunnan- Permian coalfield formation.