Abstract: Ultralaminae in Humic Coals
Fifty six humic coals, ranging in rank from 0.32% to 0.95%VRo, were examined by Transmission Electron Microscopy in ultrathin sections and optical microscopy in thin sections. Coal samples were selected from late Carboniferous Taiyuan Formation and early Permian Shanxi Formation of Eastern part of North China, early Jurassic Badaowan Formation and middle Jurassic Xishanyao Formation of Northwest China respectively. Ultralaminaes were clearly observed at the magnification 10,000 to 60,000 scale in 29 of the 56 coals. Ultralaminae may occur as solitary, interval and aggregate forms in humic coals, the two former are mainly in collinite matrix, especially in desmocollinite, the latter mainly in bituminite or lamalginite strands. Depending on the analyzed coal, the thickness of ultralaminae varies from 10 to 80 nm. The abundance of ultralaminae in desmcollinite are various, most of coals from Taiyuan Formation and Badaowan Formation clearly show the presence of ultralaminae dispersed in humic matrix, otherwise, most of coals from Shanxi Formation and Xishanyao Formation show the absence of ultralaminae in humic matrix. vitrinite with ultralaminae usually are perhydrous vitrinite. Ultralaminae origins from selective preservation of the thin resistant outer walls of microalgae. Submicroscopically, ultralaminaes are important forms of algae. The apparent presence of ultralaminae in humic coals reflect significant contribution of algae during the humic coal formation, and algae material certainly far more widely spread through the humic coals than invisible as alginite. some bituminite are predominately composed of ultralaminae, which indicate that some bituminite actually originate from selective preservation of of the thin resistant outer walls of microalgae.
AAPG Search and Discovery Article #90939©1997 AAPG Eastern Section and TSOP, Lexington, Kentucky