摘要
本文主要研究“江南古陆”两侧二叠纪煤变质作用、海泡石成矿作用的特点和分布规律,煤变质作用与海泡石相转化的关系、以及古温度对海泡石矿物相转化的意义。作者认为二叠纪煤变质特征与海泡石相转化呈同步变化,在区域分布上低变质煤带分布着海泡石,高变质煤带分布着滑石。煤中壳质显微组分是海泡石存在的指示标志。第Ⅲ阶段肥煤的形成温度是海泡石矿物相转化的临界温度。 本文根据镜质组反射率资料,采用TTI法和卡韦尔图解分析古地温的方法,确定区内海泡石形成温度不超过120℃。
There are two coal series: Liangshan coal measure (early Permian) and Longtan coal measure (late Permian) underlying and/or overlying the sepi-clite-bearing strata (early Permian) respectively, and accumulating beside the 'Jiangnan Oldland'.The study of metamorphism of coal measures is available in assessing the sepiolite resource.The degree of coalification in this area may rover the coal rank from bituminous coal to anthracite (Ⅰ to Ⅳ stages), except brown coal (0 stage), whereas the series of the sepiolite phase-transformation is sepiolite-steven-site-talc. These two series are closely concordant each other in the regional distribution, the lower degree zones of coalification (lignite to fat coal) are related to sepiolite, higher ones (maggie to anthracite) to talc, and medium ones (coking coal to lean coal) to stevensite, talc and illite districts.Coal seams occurring in sepiolite districts have their own special mace-ral groups. The exinite as an important prospecting criterion is present in sepiolite areas and has concordant relationship with the degree of sepiolite phase-transformation during coalification progress. Thus, the sepiolite may occur Mg-clay layers wherever the maceral groups in underlying or overlying coal seams contain much more exinite.Similar to coalification, the main control factors for sepiolite phase-transformation are temperature, pressure and time, of which, temperature is an essential factor. In this paper, palao temperature for forming sepiolite is determined by the coal metamorphic 'law'. The preservation of sepiolite in strata depends on the geothermal condition of palaobasin during burial history. According to the author's calculation, the palaotemperature for forming lower degree of coalification, especially for fat coal (Ⅲ stage) may serve as the critical temperature (130℃)for forming sepiolite, above the temperature sepiolite would disappear. The important and accurate mean to be used to analyse the paleotempe-rature is the vitrinite reflectance measurement. So there i
出处
《地球学报》
EI
CAS
CSCD
1991年第3期31-46,共16页
Acta Geoscientica Sinica
