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DOI	10.1016/j.mex.2021.101511
	Clay minerals identification in rock varnish by XRD: A one-step reduction approach
	Chaddha, Amritpal Singh; Sharma, Anupam; Singh, Narendra Kumar
通讯作者	Sharma, A (corresponding author), Birbal Sahni Inst Palaeosci, Lucknow 226007, Uttar Pradesh, India.
来源期刊	METHODSX
EISSN	2215-0161
出版年	2021
卷号	8
英文摘要	Rock varnishes are known to be fine, dark, glossy submicron films found in deserts bare rock surfaces. The oxides and hydroxides of manganese and iron bind together the clay minerals present in the varnish layer. The processes of oxide-hydroxide accumulation at varnish sites are due to iron and manganese oxidizing bacteria which may require clay minerals for additional nutrition. Quantification and identification of clay minerals in this biofilm is needed to understand its formation. Past attempts to analyze the mineralogical composition of rock varnish have led to inconclusive results as varnish is a submicron thin layer composed of a complex mineral matrix. The elimination of non-crystalline cementing groups comprising of free iron oxides is a key step in the identification of many types of clay minerals, particularly in soil/sediment mineral studies. The Fe-Mn oxide-hydroxide coatings, acting as cementing materials, can be easily removed using a one-step reduction method employing Na2S2O4 at 70 degrees C, leading to separation of clay minerals. We have taken the lead from earlier reported Jackson (1958) method, wherein a combination of reagents was used such as sodium acetate, sodium citrate, hydrogen peroxide, sodium bicarbonate, and sodium dithionite for removing carbonate, organic carbon and Fe-Mn oxy-hydroxide coatings respectively from sediment grains to segregate individual grains from each other. Our modification helps in the unveiling of clay minerals from a solid substrate and reports the X-ray diffraction peaks, which are elsewise hard to detect and therefore earlier studies are inconclusive. (C) 2021 Published by Elsevier B.V.
英文关键词	Rock/desert varnish Clay mineralogy Reduction by sodium dithionite
类型	Article
语种	英语
开放获取类型	gold
收录类别	ESCI
WOS记录号	WOS:000707160400023
WOS关键词	X-RAY-DIFFRACTION ; ILLITE CRYSTALLINITY ; LADAKH ; BASIN
WOS类目	Multidisciplinary Sciences
WOS研究方向	Science & Technology - Other Topics
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/364164
作者单位	[Chaddha, Amritpal Singh; Sharma, Anupam] Birbal Sahni Inst Palaeosci, Lucknow 226007, Uttar Pradesh, India; [Chaddha, Amritpal Singh; Singh, Narendra Kumar] Univ Lucknow, Dept Chem, Lucknow 226007, Uttar Pradesh, India
推荐引用方式 GB/T 7714	Chaddha, Amritpal Singh,Sharma, Anupam,Singh, Narendra Kumar. Clay minerals identification in rock varnish by XRD: A one-step reduction approach[J],2021,8.
APA	Chaddha, Amritpal Singh,Sharma, Anupam,&Singh, Narendra Kumar.(2021).Clay minerals identification in rock varnish by XRD: A one-step reduction approach.METHODSX,8.
MLA	Chaddha, Amritpal Singh,et al."Clay minerals identification in rock varnish by XRD: A one-step reduction approach".METHODSX 8(2021).