摘要
若尔盖盆地是黄河上游重要的水源涵养地,其草地沙漠化问题日趋严重,确定沙源是防治土地沙漠化迫在眉睫的关键问题。通过扫描电镜矿物分析法对若尔盖盆地玛曲现代地表沙丘与潜在物源区进行矿物组合分析,为追溯沙丘沙源提供直接证据。研究表明:沙丘与潜在物源区沉积物的重矿物组成以角闪石(5.36%)、石榴子石(4.30%)、磷灰石(0.73%)、阳起石(0.64%)、绿帘石(0.59%)、电气石(0.57%)、金红石(0.54%)、褐帘石(0.41%)、铁辉石(0.35%)、铁橄榄石(0.27%)、榍石(0.23%)、黝帘石(0.18%)、透辉石(0.18%)、锆石(0.11%)和针铁矿(0.05%)等为主,轻矿物主要是长石(34.36%)和石英(23.54%)。玛曲样品的风化指标CIA与Q/TF均处低值,重矿物组成不受HMC、t HMC和SRD指数所指示的水力分选和成岩溶解作用影响,现代沙丘样品的重矿物指数(W、ZTR、GZi和ATi)与潜在物源区变化一致,结合主成分分析,揭示了现代沙丘沙源来自于风力对若尔盖盆地古河湖相沙和古风成沙的再次搬运,为区域生态环境治理提供了矿物学依据。
Background,aim,and scope The Zoige Basin,located at the northeastern part of the Qinghai-Xizang Plateau,serves as a vital water conservation area for the upper reaches of the Yellow River.Nevertheless,grassland desertification has become a prominent issue in this region due to the combined effects of global warming and increased anthropogenic activities.Desertified land is expanding at an annual rate of 6.8%,with the total area surpassing 3200 km2,threatening the basin’s water conservation function.Accurately identifying the provenance of the modern dunes is essential for study of the dune formations and the development of effective desertification mitigation strategies.However,previous research lacks direct mineralogical evidence,and there is still controversy surrounding the sand sources of the dunes.This study seeks to fill this research gap by conducting a comprehensive analysis of the mineral compositions of modern dunes and their potential source areas,thereby establishing a scientific foundation for ecological restoration efforts.Materials and methods In this study,sand samples from dunes and samples from potential source areas in the Zoige Basin were collected.Using scanning electron microscopy,a systematic analysis of the mineral assemblages of these samples was conducted.By comparing the mineral assemblages of the source areas and the dune samples,provenance tracing was performed.The CIA and Q/TF indices in the mineral assemblages were used to ref lect the degree of weathering of the sediments.The HMC,tHMC,and SRD indices were employed to constrain the extent to which the mineral assemblages of the sediments were inf luenced by hydraulic sorting and diagenetic processes.The mineralogical indices(such as ZTR,GZI,and ATI)were used to indicate the lithological characteristics of the source areas.Results The light minerals in surface samples of modern sand dunes and potential source areas mainly include quartz,potassium feldspar,sodium feldspar,muscovite,white garnet,plagioclase,calcite,dolomite,kaolinite,and talc.The heavy minerals mainly include chlorite,amphibole,garnet,goethite,apatite,pyroxene,titanium iron oxide,epidote,rutile,tourmaline,biotite,garnet,pyroxene,garnet,diopside,epidote,pyroxene,jadeite,olivine,and zircon.The average content of heavy mineral phases is 17.88%.The heavy minerals with abundant content are amphibole(2.22%-16.40%)and garnet(1.81%-6.79%),while the more abundant ones include goethite(limonite),apatite,actinolite,titanium oxide,epidote,rutile,tourmaline,biotite,and rhodochrosite.Discussion The CIA and Q/TF of Maqu samples are both low,indicating that the sediments have been less affected by chemical weathering.Moreover,the HMC index suggests that the heavy mineral assemblages have not been significantly inf luenced by hydraulic sorting or subsequent diagenetic processes.This indicates that the mineral assemblages are primarily controlled by provenance.The ZTR,GZI,and ATI indices show that the modern dune surface samples are consistent with the potential source areas.Combined with a principal component analysis(PCA)confidence interval exceeding 95%and considering the surface processes of modern dune formation,the results indicate that river and lake sediments,along with ancient aeolian sands,are the primary sand sources for the formation of modern dunes.Conclusions Contemporary dunes in the Zoige Basin predominantly originate from the reworking of ancient fluvial-lacustrine sediments and aeolian sands present within the basin,rather than from external sources.The application of the QEMSCAN-based mineral analysis technique provides a rigorous and quantitative framework for provenance tracing,facilitating the precise identification of sand sources.Recommendations and perspectives The mineral analysis method enables accurate determination of the sand source of modern dunes and provide scientific evidence for ecological control.Relevant agencies can therefore carry out targeted sand source control measures.This research highlights urgent need for the implementation of targeted management strategies,including the stabilization of exposed ancient sedimentary layers and the restoration of vegetation in regions susceptible to aeolian processes,in order to mitigate desertification in this ecologically sensitive area.
作者
张津
周亚利
周家和
朱燕燕
马宝峰
田娅琪
ZHANG Jin;ZHOU Yali;ZHOU Jiahe;ZHU Yanyan;MA Baofeng;TIAN Yaqi(School of Geography and Tourism,Shaanxi Normal University,Xi’an 710119,China)
出处
《地球环境学报》
2025年第3期316-332,共17页
Journal of Earth Environment
基金
国家自然科学基金项目(42071112)。
关键词
若尔盖盆地
扫描电镜
沙丘
物源示踪
Zoige Basin
scanning electron microscopy
sand dunes
material source tracing
作者简介
通信作者:周亚利,E-mail:ylzhou109@163.com。
