干旱区生态环境知识资源中心(Arid): 印度德干高原砖红壤与玄武岩风化红土磁学性质及其成因分析

Arid

	印度德干高原砖红壤与玄武岩风化红土磁学性质及其成因分析
其他题名	MAGNETIC PROPERTIES OF LATERITE AND ITS ORIGIN IN DECCAN PLATEAU, INDIA
	袁毓婕 1; 刘秀铭 1; 吕镔 1; 马明明 1; 王涛2 ; 陈秀玲 1
来源期刊	第四纪研究
ISSN	1001-7410
出版年	2017
卷号	37 期号:1 页码:67-81
中文摘要	印度中西部德干高原是由白垩纪末期65Ma以前多次喷发的玄武岩形成的高原。喷发间歇期间玄武岩遭受风化,形成了多层玄武岩风化红层。德干高原就是由这样一层层的溢流喷发玄武岩和风化红层相间而成,厚度达千米以上。在德干高原和南方各地的顶部普遍发育着砖红壤,该砖红壤在德干高原发育约25m厚,被认为是从玄武岩母质基础上原地风化形成,但是实地观察发现,砖红壤与玄武岩风化红土在结构、构造以及物质组成等方面均存在明显差别。常见的玄武岩喷发间歇发育的风化层厚2~3m,存在从上到下风化程度由强到弱,最后过渡到玄武岩母岩的明显层次与颜色的变化。但是德干高原玄武岩之上的25m厚砖红壤缺乏这种渐变特征,而且平坦的砖红壤顶部洼地中还发现了风积黄土层。对德干高原砖红壤、玄武岩以及玄武岩风化红土层分别采样,测量其全样粒度和磁化率、饱和磁化强度、饱和等温剩磁、非磁滞剩磁等常温磁学参数,挑选代表性样品进行磁滞回线和热磁分析。实验结果表明:1)砖红壤样品主要的磁性矿物是赤铁矿,有些同时还含微量磁赤铁矿,粒径相对较粗的玄武岩风化红土层的主要磁性矿物是磁铁矿和磁赤铁矿;2)玄武岩只含磁铁矿,并无磁赤铁矿或者赤铁矿。因此,不论是玄武岩风化红土,还是砖红壤,它们所含的磁赤铁矿以及赤铁矿都是在风化成土过程中形成的。砖红壤以赤铁矿为主和少量针铁矿,偶有样品含微量磁赤铁矿,说明该磁赤铁矿可能是母岩中的磁铁矿风化为赤铁矿的中间产物;3)玄武岩风化红土层与砖红壤不仅在磁性矿物特征方面存在差别,而且在全样粒度组成方面也存在明显差别,前者以>100mum为主,而后者以<100mum为主。此外,25m厚层状砖红壤除了缺乏由上而下风化程度由强变弱的差异与层次的特征之外,也缺乏砖红壤中残留的玄武岩碎屑,难以支持巨厚砖红壤由顶层玄武岩就地风化形成的说法。砖红壤厚层均匀特征似乎需要自下而上形成过程,即不断加入物质不断地风化成土才能够形成均匀厚层砖红壤。目前刚刚发现了徳干高原黄土堆积,其西北方向分布着印度沙漠,每年都有沙尘暴发生,向德干高原提供着物质来源。因此,砖红壤由风积物加积形成或许是要考虑的重要可能性之一。
英文摘要	Deccan Plateau (15。27.281 ′~22。18.835’N,72。34.686’~ 79。49.903’E) located in the mid-western India is comprised by many layers of basalt erupted by Late Cretaceous. These basalt layers are interbedded with red soils(about 2~3m) weathered from basalt (or RSB, red soils basalt). Laterite is commonly developed in the top of the plateau and large area of South India. The thickness of laterite in top of plateau is about 25m, which is thought to be formed by basalt in situ weathering. However it was questioned by some investigators due to its missingweathering horizons from top to bottom. On the contrary, the RSB with thickness of 3m shows obviously weathering differences with depth. In this study, 18 samples (9 laterite; 3 basalt, and 6 RSB) in Deccan Plateau were collected. Detailed measurements for grain size and magnetic parameters were carried out. The results show that(1) The main magnetic minerals of laterite are hematite, and may contain a little maghemite as well; while the dominant magnetic minerals in basalt soils are magnetite and maghemite; (2) The basalt contains magnetite only, therefore, maghemite and hematite detected from weathered basalt soil were formed during pedogenic process. This probably suggests that maghemite is the intermediate product in the transformation of magnetite to hematite;(3) Clear differences are observed between RSB and laterite, not only in their magnetic properties, but also in their particle-size distribution. In addition, strong weathering characteristics is detected throughout all the depth of25m, it therefore is hard to support the hypothesis of laterite formed by basalt in situ weathering. The feature of thick laterite required a pedogenic process developing from the bottom up to top gradually, inputting material and developing soils step by step. Thus laterite formed by dust deposits is put forward: aeolian aggrading and laterizing gradually generates finally 25m thickness of laterite since Late Cretaceous. This hypothesis is supported by(1) recently loess discovered on top of laterite in the plateau,(2) wind blown silt grain size of laterite,and(3) Indian desert in the northwestern providing dust every year.
中文关键词	印度砖红壤 ; 德干高原玄武岩 ; 玄武岩风化红土 ; 砖红壤红土 ; 砖红壤成因
英文关键词	Indian laterite Deccan Plateau basalt weathered basalt red soils laterite origin
语种	中文
国家	中国
收录类别	CSCD
WOS类目	GEOSCIENCES MULTIDISCIPLINARY ; GEOLOGY
WOS研究方向	Geology
CSCD记录号	CSCD:5906414
来源机构	中国科学院西北生态环境资源研究院
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/235831
作者单位	1.福建师范大学地理科学学院, 湿润亚热带山地生态国家重点实验室培育基地, 福州, 福建 350007, 中国; 2.中国科学院西北生态环境资源研究院, 中国科学院沙漠与沙漠化重点实验室, 兰州, 甘肃 730000, 中国
推荐引用方式 GB/T 7714	袁毓婕,刘秀铭,吕镔,等. 印度德干高原砖红壤与玄武岩风化红土磁学性质及其成因分析[J]. 中国科学院西北生态环境资源研究院,2017,37(1):67-81.
APA	袁毓婕,刘秀铭,吕镔,马明明,王涛,&陈秀玲.(2017).印度德干高原砖红壤与玄武岩风化红土磁学性质及其成因分析.第四纪研究,37(1),67-81.
MLA	袁毓婕,et al."印度德干高原砖红壤与玄武岩风化红土磁学性质及其成因分析".第四纪研究 37.1(2017):67-81.