摘要
鄂尔多斯盆地东北缘黑岱沟太原组顶部6号煤层属于低等煤化程度的低硫烟煤,其中铝土质粘土岩、煤层中超常含有勃姆铝石,发现超常含镓、超常富集稀土,7段煤层平均含Ga44.8μg/g、含∑REE110.82～467.21μg/g,显示出铝、镓、稀土元素三者地球化学行为的相似性和共生特性。是特殊地质背景与古沉积环境下的产物。研究认为,铝、镓、稀土元素三者有共同的来源:①古老基底剥蚀区,古陆富钾高铝的岩浆岩与变质岩建造;②中奥陶统顶部风化剥蚀面产出的上石炭统本溪组粘土层及铝土层中富集的镓是重要来源;③煤层系中粘土质砾岩中发现显量火山晶屑及火山灰,部分提供易分解的铝-镓物源;④下二叠统太原组海陆交互滨海-潟湖相、三角洲相、堡岛与沼湖沉积岩相古地理优越,是煤层与铝土质粘土层发育集中富集含镓的良好沉积古环境。总之,镓的物源具有多来源、继承性、分时期、有阶段复杂富集的特点。
The No. 6 coal seam lies in the upper part of Taiyuan Formation within the Hada Gol Ga-bearing coal deposit of northeastern Ordos Basin. This coal seam is a low sulfidation type of bituminous coal with low coalification. Due to the special geological background and paleosedimentary environment,the bauxitic clay stone and the coal seam are extremely enriched in boehmite,Ga and REE. The average content of Ga is 44.8ug/g, and the ∑REE values vary from 110.82ug/g to 467.21ug/g in seven coal segments, suggesting that AI, Ga and R.EE have similar geochemical behaviors and coexistence features. It is considered that Al, Ga and REE were derived from the same sources： （1） the erosion area of paleobasement, where there existed igneous rocks and metamorphic rocks with high K and Al; （2） clay stone and bauxite in Upper Carboniferous Benxi Formation overlying Middle Ordovician might have been an important provenance of Ga; （3） clayey glutenite in coal measure strata is characterized by volcanic crystal fragments and volcanic ash,implying that they partly provided dissolvable Al and Ga materials; （4） Lower Permian Taiyuan Formation comprises such continental-marine interactive deposits as offshore coastal deposit, lagoonal deposit, delta deposit, barrier island deposit and lakemarsh sedimentary system. Such lithofacies paleogeography served as an advantage sedimentary environment of coal seams and bauxite strata for the accumulation of Ga. It is thus known that the origin of Ga in coal is characterized by multi-sources, inheritance, multiple periods and certain steps, suggesting that the accumulation process of Ga was very complicated.
出处
《中国地质》
CAS
CSCD
北大核心
2009年第2期417-423,共7页
Geology in China
基金
国家重点基础研究发展规划项目(2003CB214607)资助。
关键词
太原组6号煤层
煤中镓
多来源-继承性-分时期-有阶段
准格尔旗黑岱沟
鄂尔多斯盆地
内蒙古
The No. 6 coal seam of Taiyuan Formation
Ga deposit in coal seam
multisource-inheritancemultiple periods-certain steps
Hada Gol in Jungar Banner
Ordos Basin
Inner Mongolia
