Coal Deformation, Metamorphism and Tectonic Environment in Xinhua, Hunan

Abstract

This article discusses in detail chemical composition, molecular structure, microstructure phenomena, estimate of the palaeo-stress, paleo-temperature and the strain rate to deepen the knowledge for the correlation of coal deformation and metamorphism with structural environment in Xinhua Hunan by coal quality analysis, XRD and SEM methods, which provide dependable theoretical foundation for coal resource exploitation and utilization. The results show that 1) d002 value of six coal samples is from 3.36 to 3.39 nm, coal resolved itself into aphanitic graphite with the increase of coal rank during coalification, which is characterized by graphite flakes, and the crystallite size is from 50 nm to 250 nm; A certain degree of 3R-structure content is increases and the crystallite size is extend with the coalification process, but RH-structure content is decreased; 2) the tectonic environment of research area belongs to the ductile-brittle deformation, which was characterized by low temperature, low stress, high strain rate; 3) Tianlongshan magmatic intrusion provided heat source, its side-extrusion made the molecules structure of coal ordering, distance between layers decreased, finally it caused the formation of aphanitic graphite.

Analysis of metamorphism and tendency of black coals to spontaneous combustion

“…Clear boundaries between the groups according to endogenous fire hazard on the basis of genetic signs have not been established, since there is no normative base for their determination. This situation is confirmed by studies [3,6,10] on the establishment of coal groups according to the degree of coalification using three indicators -V daf , coal grade (M) and carbonization (C n ). The carbonization index characterizes the elemental composition, which is defined as the quantitative ratio of the carbon content to the sum of oxygen and hydrogen, calculated on dry and ashless mass.…”

“…and geological conditions. Many classifications of metamorphic processes have been proposed [6], based on various principles and reduced to numerous names of types and species.…”

On Determining the Coal Carbonization Indicator for Establishment of Mine Fire Hazard Groups

“…В даний час шахтопласти (виїмкові поля) за схильністю вугілля до самозаймання, відповідно до інструкції [1], поділяються на три групи ендогенної пожежонебезпеки: Іособливо небезпечні; ІІнебезпечні; ІІІмалонебезпечні. Паралельно з такою градацією встановлена [2,3] залежність ендогенної пожежонебезпеки від впливу головних чинників. До них були віднесені: ступінь вуглефікації, вміст загальної сірки, потужність пластів, що розробляються та їх будова, наявність тектонічних порушень.…”

“…Цю ситуацію підтверджують дослідження [2,3] по встановленню груп вугілля за ступенем вуглефікації з застосуванням трьох показників -V daf , марки вугілля (М) і карбонізації (С п ). Слід зазначити, що обрані показники частково корелюють між собою і кожен з них не в повній мірі відображає перетворення вугілля в процесі метаморфізму.…”

Peculiarities of using classification indicators of the coal metamorphism degree for predicting the hazardous coal seams properties

“…The conditions for the formation of metamorphic rocks in general [3] and fossil coals in particular [4 -7] practically do not differ from each other. It is assumed that the processes of metamorphism occurred in past geological periods at a temperature of 200 -650ºС at a depth of 10 -40 km [8,9].…”