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1.
LIU Pengde 《干旱区科学》2021,13(11):1163-1182
West Junggar is a key area for understanding intra-oceanic plate subduction and the final closure of the Junggar Ocean. Knowledge of the Carboniferous tectonic evolution of the Junggar Ocean region is required for understanding the tectonic framework and accretionary processes in West Junggar, Central Asian Orogenic Belt. A series of Early Carboniferous volcanic and intrusive rocks, namely, basaltic andesite, andesite, dacite, and diorite, occur in the Mayile area of southern West Junggar, northwestern China. Our new LA-ICPMS zircon U-Pb geochronological data reveal that diorite intruded at 334 (±1) Ma, and that basaltic andesite was erupted at 334 (±4) Ma. These intrusive and volcanic rocks are calc-alkaline, display moderate MgO (1.62%-4.18%) contents and Mg# values (40-59), and low Cr (14.5×10-6-47.2×10-6) and Ni (7.5×10-6-34.6×10-6) contents, and are characterized by enrichment in light rare-earth elements and large-ion lithophile elements and depletion in heavy rare-earth elements and high-field-strength elements, meaning that they belong to typical subduction-zone island-arc magma. The samples show low initial 87Sr/86Sr ratios (range of 0.703649-0.705008), positive εNd(t) values (range of 4.8-6.2 and mean of 5.4), and young TDM Nd model ages ranging from 1016 to 616 Ma, indicating a magmatic origin from depleted mantle involving partial melting of 10%-25% garnet and spinel lherzolite. Combining our results with those of previous studies, we suggest that these rocks were formed as a result of northwestward subduction of the Junggar oceanic plate, which caused partial melting of sub-arc mantle. We conclude that intra-oceanic arc magmatism was extensive in West Junggar during the Early Carboniferous. 相似文献
2.
淮河上游全新世黄土-古土壤序列元素地球化学特性研究 总被引:6,自引:0,他引:6
在野外考察研究的基础上,对河南禹州全新世风成黄土-古土壤剖面系统采样,利用X-荧光光谱仪测定了常量元素和微量元素的含量及其变化,并与磁化率曲线、粒度变化曲线对比分析发现:常量元素氧化物比值钾钠比、残积系数和以Rb为代表的微量元素含量等随剖面层次呈规律性变化,即在古土壤层(S0)中含量最高,表土层(MS)中次之,在黄土层(L1、Lt、L0)中最低。硅铝率和Sr的含量表现出相反的变化规律。表明在全新世古土壤层和表土层形成时期,气候温暖湿润,成壤作用和次生粘化作用较强;在黄土堆积时期,气候比较干旱,沙尘暴频繁,成壤作用微弱。这些化学参数与磁化率曲线可以进行对比,表明成土过程中元素的迁移变化受全新世以来气候变化和成壤环境变化的控制。与黄土高原腹地的洛川剖面相比,淮河上游禹州剖面中绝大多数常量元素的含量较高,而绝大多数微量元素的含量偏低,磁化率也显著偏低,绝对值差别很大,粒度组成当中细沙成分含量很高,这说明淮河上游黄土物质来源与黄土高原地区明显不同。联系全新世时期黄河频繁泛滥、改道、沉积与黄淮平原盛行东北风形成流沙地的事实,认为淮河上游的黄土是黄河泛滥沉积物质经过风沙活动改造,由东北风力系统搬运而来的近源粉尘堆积,再经过就地风化或者成土改造而形成。 相似文献
3.
华南海岛土壤形成的地球化学 总被引:5,自引:0,他引:5
The soils in South China sea Islands(SCSI)were divided into three types,nmaely,phospho-calc soils,skeletisols and coastic solonchake,which were derived from bio-clastic and strongly calcareous sediments.In comparison with their parent materials,the phospho-Calc soils have higher contents of P,Zn Cu,Ba,and Cd,which tend to increase gradually with time,and lower contents of Mg,Ca,Sr,B,V,Pb,and Mo,which tend to decrease by degrees with time,The above-mentioned constituents in skeletisols and coastic solonchaks are similar to those in their parent materials except for P and Na,The factors affecting element distribution are mainly special bioclimate and parent material,meanwhile,resulting in the remakable influence on element distribution through soil-forming time. 相似文献
4.
5.
出生缺陷高发区土壤微量元素含量特征的空间信息分析 总被引:2,自引:0,他引:2
从土壤元素含量分布与出生缺陷发生率高低的相关性入手,探讨出生缺陷高发区土壤元素含量的异常特征,为筛选诱发出生缺陷的敏感因子提供科学依据和新的途径.选取出生缺陷高发的山西省中阳和交口两县为研究区,根据流行病调查路线和村镇,逐村采集土壤样品,分析测定土壤样品中Al、As、Ca、Cu、Fe、K、Mg、Mo、Na、Ni、Pb、Se、Sn、Sr、V、Zn等16种元素含量.运用ArcGIS 9.0软件,绘制研究区内96个采样点的出生缺陷发生率和土壤中16种元素含量分布的专题图,并进行Kriging插值和叠加分析.结果显示,出生缺陷发生率高低的空间变异趋势与土壤元素含量分布趋势具有一定的相似性.其中元素V、Se、Mo、As、Mg、Na含量与出生缺陷发生率变化的空间相关性较大.土壤中V、Se的低含量和Mo、As的高含量可能是造成出生缺陷高发的原因.说明土壤元素含量异常与出生缺陷发生率之间存在相关关系. 相似文献
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7.
研究西南地区变性土、铁铝土及水稻土7个剖面的地球化学和矿物学特征的结果表明:铁铝土在元素地球化学分类上可划为铝质富铝化类型,变性土也表现了一定的富铝化趋势,而水稻土最明显的特征是Fe、Mn及Ca均相对富集。变性土粘土矿物以蒙脱石为主,铁铝土则以高岭石占优势,水稻土矿物组成取决于母质来源。根据主组元分析结果,可以探讨成土过程中不同剖面的元素分异和相关性,以及元素地球化学的演变趋势。 相似文献
8.
Evaluation of the stoichiometry of base cations (BCs, including K+, Na+, Ca2+, and Mg2+) and silicon (Si) (BCs:Si) during soil mineral weathering is essential to accurately quantify soil acidification rates. The aim of this study was to explore the differences and influencing factors of BCs:Si values of different soil genetic horizons in a deep soil profile derived from granite with different extents of mineral weathering. Soil type was typic acidi-udic Argosol. Soil samples were collected from Guangzhou, China, which is located in a subtropical region. To ensure that the BCs and Si originated from the mineral weathering process, soil exchangeable BCs were washed with an elution treatment. The BCs:Si values during weathering were obtained through a simulated acid rain leaching experiment using the batch method. Results showed that soil physical, chemical, and mineralogical properties varied from the surface horizon to saprolite in the soil profile. The BCs:Si values of soil genetic horizons during weathering were 0.3-3.7. The BCs:Si value was 1.7 in the surface horizon (A), 1.1-3.7 in the argillic horizon (Bt), and 0.3-0.4 in the cambic (Bw) and transition (BC) horizons, as well as in horizon C (saprolite). The general pattern of BCs:Si values in the different horizons was as follows: Bt > A > Bw, BC, and C. Although BCs:Si values were influenced by weathering intensity, they did not correlate with the chemical index of alteration (CIA). The release amounts of Si and BCs are the joined impact of soil mineral composition and physical and chemical properties. A comprehensive analysis showed that the BCs:Si values of the soil derived from granite in this study were a combined result of the following factors: soil clay, feldspar, kaolinite, organic matter, pH, and CIA. The main controlling factors of BCs:Si in soils of different parent material types require extensive research. The wide variance of BCs:Si values in the deep soil profile indicated that H+ consumed by soil mineral weathering was very dissimilar in the soils with different weathering intensities derived from the same parent material. Therefore, the estimation of the soil acidification rate based on H+ biogeochemistry should consider the specific BCs:Si value. 相似文献
9.
西安市郊农田土壤环境地球化学研究 总被引:1,自引:0,他引:1
通过取样调查和实验分析,研究了西安市郊农田土壤环境的地球化学特征。土壤中的常量元素和微量元素结果分析显示,CaO、MgO和Na2O含量明显高于陕西土壤、全国土壤中的平均值,重金属元素Pb、Ni、Zn、Cr、Co、Mn、As等严重超标。通过相关分析和聚类分析,探讨了土壤元素间的亲和性及赋存特征,为农业生产、农业结构调整和防治土壤污染提供地球化学依据。 相似文献
10.