西菲律宾海西部沉积物磁学特征及其环境意义  

Magnetic Properties of Sediments from the Western West Philippine Sea and Their Environmental Implications

作　　者：李波[1] 石显耀[2] 李学杰[1] 李顺[1] 王艳 高红芳[1] 钟和贤[1] 田成静[1] Li Bo Shi Xianyao Li Xuejie Li Shun Wang Yan Gao Hongfang Zhong Hexian Tian Chengiing(Key Laboratory of Marine Mineral Resources, Guangzhou Marine Geological Survey, Ministry o{ Land and Resources, Guangzhou 510075, China China Geological Survey,Beiiing 100037,China Guangdong Non{errous Metals Geological Exploration Institution,Guangzhou 510080,China)

机构地区：[1]国土资源部海底矿产资源重点实验室,广州海洋地质调查局,广州510075 [2]中国地质调查局,北京100037 [3]广东省有色地质勘查院,广州510080

出　　处：《地质科技情报》2016年第5期34-41,共8页Geological Science and Technology Information

基　　金：国土资源部海底矿产资源重点实验室开放基金课题(KLMMR-2014-A-12);国家自然科学基金项目(41272384;41306042);中国地质调查局项目(GZH201300502;DD20160138;DD20160227)

摘　　要：磁学参数作为有效的气候环境变化替代指标,能为古环境演变和沉积物物源研究提供有价值的信息。对取自西菲律宾海西部的GX72柱状样沉积物进行系统的环境磁学研究,测量了磁化率(χ)、非磁滞剩磁(ARM)、等温剩磁(IRM)、磁化率变温曲线(κ-T曲线)、磁滞回线等磁学参数或曲线。结果表明,GX72柱状样沉积物中携磁矿物以低矫顽力磁铁矿为主,粒径以较粗粒准单畴(PSD)为主,这些磁性颗粒主要来源于河流输入的陆源碎屑物质,风成粉尘较少。剖面上多个磁学参数呈现出相同或相反的变化趋势,反映古气候对沉积物磁学性质的制约。χ高值样品通常对应于高饱和等温剩磁(SIRM)值、低ARM/SIRM值、低χARM/χ值以及低χfd值;这类沉积物样品中磁性矿物的含量相对更高,粒度相对较大,可能形成于冷期(相对)。相反,χ低值样品通常对应于低SIRM值、高ARM/SIRM值、高χARM/χ值以及低χfd值,这类样品中磁性矿物的含量相对较低,粒径相对较小,代表相对暖期沉积。Magnetic parameters as the effective indicator of climate and environmental change can provide valuable information for paleoenvironmental evolution and sediment provenance.Core GX72 sediments collected from the western West Philippine Sea were selected for detailed environmental magnetic analysis including magnetic susceptibility（χ）,anhysteretic remanent magnetization（ARM）,isothermal remanent magnetization（IRM）,temperature-dependent magnetic susceptibility（κ-T curves）and hysteresis loop.Results show that dominant magnetic particles in core GX72 sediments are low-coercivity magnetite with relatively coarse pseudo-single-domain（PSD）in size.These magnetic minerals mainly sourced from terrigenous detrital by riverine input and subsequently dispersed into the basin.Moreover,aeolian dust is rare in bulk sediments.Multiple magnetic parameters showing the same or the opposite trend on the profile indicate the control of paleoclimate on magnetic properties of sediments.Highχsamples usually have high SIRM（saturation IRM）,low ARM/SIRM,lowχARM/χand lowχfdvalue.We infer these samples with higher concentrations in magnetic minerals with larger coarse-grained fraction could tend to deposit in cold period.In contrast,lowχsamples usually have lowSIRM,high ARM/SIRM,highχARM/χandχfdvalue.These samples are devoid of magnetic minerals and composed of dominantly fine-grained particles which favor warm period for deposition.

关 键 词：西菲律宾海 磁学性质 古环境 物源 

分 类 号：P318.41[天文地球—固体地球物理学]