浅埋煤层烧变岩地球化学与变质矿物相特征  

Geochemistry and metamorphic mineral facies ofburned rocks in shallow coal beds

作　　者：杨帆 热西提·亚力坤 薛小渊 宋世骏 胡俭 张泽宇 姬中奎 黄雷[2] YANG Fan;YALIKUN Re Xiti;XUE Xiaoyuan;SONG Shijun;HU Jian;ZHANG Zeyu;JI Zhongkui;HUANG Lei(Shaanxi Coal and Chemical Industry Group,Shenmu Zhangjiamao Mining Co.,Ltd.,Shenmu 719316,China;State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi’an 710069,China;China Coal Technology and Engineering Group,Xi’an Research Institute(Group)Co.,Ltd.,Xi’an 710054,China;Shaaxi Key Laboratory of Prevention and Control Technology for Coal Mine Water Hazard,Xi’an 710077,China)

机构地区：[1]陕西煤业化工集团神木张家峁矿业有限公司,陕西神木719316 [2]西北大学地质学系/大陆动力学国家重点实验室,陕西西安710069 [3]中国煤炭科工西安研究院〔集团〕有限公司,陕西西安710054 [4]陕西省煤矿水害防治技术重点实验室,陕西西安710077

出　　处：《西北大学学报（自然科学版）》2024年第2期329-344,共16页Journal of Northwest University（Natural Science Edition）

基　　金：国家自然科学基金(42272148)。

摘　　要：以陕北张家峁井田延安组2^(2),3^(1)段烧变岩为研究对象,对其进行岩石地球化学迁移规律以及变质矿物相特征分析。结果表明,该区烧变岩为低碱性硅铝质变质岩,横向上钙碱性分布不均一,少部分烧变样品烧失量大且CaO含量高,Fe元素迁移聚集。Zr相容性比Hf更好,Ba元素富集可能与后期水文作用有关,稀土元素分配趋势线为略微轻稀土富集型,烧变作用对稀土元素的分配影响相对有限。烧变岩原生矿物多具有烧蚀特征,镜下发育烧蚀边、气孔构造等,新生矿物呈集合体充填矿物间或矿物裂缝中。矿物相组合与热接触变质作用中发生高热变质的透长岩相相近,但变质压力更低,温度更高。烧变岩层由下而上可分为薄层板状烧烤岩、烧熔岩、厚层板状烧烤岩、厚层层状烧烤岩的岩石组合,鳞石英+方石英相较莫来石+堇青石+赤铁矿能更好表征岩石烧变程度的强弱,同层烧烤岩下部烧变程度高于上部,烧熔岩上部板状烧烤岩烧变程度高于下部板状烧烤岩。研究区烧变岩具有“隐伏”的特点,且存在同沉积期烧变作用,除暴露在河谷阶地的烧变岩层外,部分烧变岩层埋于更新世地层和残余延安组地层之下。早期形成的烧变岩层后期被破坏,多期烧变地层相互叠置形成现今火烧区。The study focuses on the burnt rocks of the 2^(2) and 3^(1) sections of the Yan’an Formation in Zhangjiamao Coalfield,Northern Shaanxi,and analyzes their geochemical migration patterns and metamorphic mineral facies characteristics.The results indicate that the burnt rocks in this area are low alkaline silicoaluminal metamorphic rocks,with uneven distribution of calcium and alkali horizontally.A small number of burnt rock samples have high loss on ignition and high CaO content,with Fe elements migrate and accumulate.Zr has better compatibility than Hf,and the enrichment of Ba element may be related to later hydrological processes.The trend line of rare earth element distribution is little L-REE enrichment,and the effect of burning on the distribution of rare earth elements is relatively limited.The primary minerals in burnt rocks often exhibit ablative characteristics,with the development of ablative edges and pore structures under the microscope.Newly formed minerals form aggregates and fill mineral spaces or fractures.The mineral facies combination is similar to the diorite facies that undergoes high thermal metamorphism during thermal contact metamorphism,but the metamorphic pressure is lower and the temperature is higher.The burnt rock layers can be divided from bottom to top into a combination of thin plate-like burnt rock,burnt lava,thick plate-like burnt rock,and thick layered burnt rock.tridymite+cristobalite content can better characterize the burning degreecompared to mullite+cordierite+hematite content.The degree of burning in the lower part of the same layer burnt rock is higher than that in the upper part,and the burning degree of plate-like burnt rock in the upper part of the burnt lava is higher than that in the lower part.The burnt rocks in the research area have the"hidden"characteristic and have the same sedimentary period burnt effect.Except for the burnt rock layers exposed in the valley terrace,some of the burnt rock layers are buried under the Pleistocene strata and residual yan’an Forma

关 键 词：烧变岩 张家峁井田 地球化学 变质矿物相 热接触变质作用 透长岩相 

分 类 号：P618.11[天文地球—矿床学]