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961.
962.
土壤元素背景值是土壤环境现状研究的重要内容,查清土壤中元素的含量及分布特征,可为区域环境质量评价、土壤环境标准制定、土地资源优化以及地方性疾病的防治提供科学依据。对广东韶关地区3 969件表层土壤样品中54项元素(指标)进行了研究,并与中国土壤A层背景值及广东土壤A层背景值进行对比。结果表明:韶关地区土壤中聚集了与成矿作用密切相关的元素,并形成高背景场,Mo、I、Br、Ag等元素相对贫乏;成土母质是土壤环境背景值最重要的影响因素,不同母质的土壤元素背景值差异较大;土壤类型及土壤有机质含量对土壤环境背景值有一定的影响,总体来看,黄壤、黄红壤、石灰土为区内大部分元素高背景值土壤类型,红壤与潴育性水稻土的环境背景值大致与全区的背景值相当;赤红壤、紫色土中大部分元素背景值较低,有机质含量与土壤元素背景值呈正相关关系。 相似文献
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965.
The early Paleozoic tectonic evolution of the Xing'an-Mongolian Orogenic Belt is dominated by two oceanic basins on the northwestern and southeastern sides of the Xing'an Block,i.e.,the Xinlin-Xiguitu Ocean and the Nenjiang Ocean.However,the early development of the Nenjiang Ocean remains unclear.Here,we present zircon U-Pb geochronology and whole-rock elemental and Sr-Nd isotopic data on the gabbros in the Xinglong area together with andesitic tuffs and basalts in the Duobaoshan area.LA-ICP-MS zircon U-Pb dating of gabbros and andesitic tuffs yielded crystallization ages of 443-436 Ma and 452-451 Ma,respectively.The Early Silurian Xinglong gabbros show calc-alkaline and E-MORB affinities but they are enriched in LILEs,and depleted in HFSEs,with relatively low U/Th ratios of 0.18-0.36 andεNd(t)values of-1.6 to+0.5.These geochemical features suggest that the gabbros might originate from a mantle wedge modified by pelagic sediment-derived melts,consistent with a back-arc basin setting.By contrast,the andesitic tuffs are characterized by high MgO(>5 wt.%),Cr(138-200 ppm),and Ni(65-110 ppm)contents,and can be termed as high-Mg andesites.Their low Sr/Y ratios of 15.98-17.15 and U/Th values of 0.24-0.25 and moderate(La/Sm)_n values of 3.07-3.26 are similar to those from the Setouchi Volcanic Belt(SW Japan),and are thought to be derived from partial melting of subducted sediments,and subsequent melt-mantle interaction.The Duobaoshan basalts have high Nb(8.44-10.30 ppm)and TiO2 contents(1.17-1.60 wt.%),typical of Nb-enriched basalts.They are slightly younger than regional adakitic rocks and have positiveεNd(t)values of+5.2 to+5.7 and are interpreted to be generated by partial melting of a depleted mantle source metasomatized by earlier adakitic melts.Synthesized with coeval arc-related igneous rocks from the southeastern Xing'an Block,we propose that the Duobaoshan high-Mg andesitic tuffs and Nbenriched basalts are parts of the Late Ordovician and Silurian Sonid Zuoqi-Duobaoshan arc belt,and they were formed by the northwestern subduction of the Nenjiang Ocean.Such a subduction beneath the integrated Xing'an-Erguna Block also gave rise to the East Ujimqin-Xinglong igneous belt in a continental back-arc basin setting.Our new data support an early Paleozoic arc-back-arc model in the northern Great Xing'an Range. 相似文献
966.
Xiao Yang Zhao Chang Sun Yue Wang Shun Wu Huanran Chen Hui Liu Hanlong 《Acta Geotechnica》2021,16(5):1391-1400
Acta Geotechnica - One-dimensional compression tests on quartz sands treated by microbially induced carbonate precipitation (MICP) were carried out to evaluate the effects of gradation and calcium... 相似文献
967.
Xiao Yang Wang Yang Wang Shun Evans T. Matthew Stuedlein Armin W. Chu Jian Zhao Chang Wu Huanran Liu Hanlong 《Acta Geotechnica》2021,16(5):1417-1427
Acta Geotechnica - Microbially induced carbonate precipitation (MICP) has been actively investigated as a promising method to improve soil properties. A burning issue impeding its wide application... 相似文献
968.
Zhong Wenhan Liu Hanlong Wang Qi Zhang Wengang Li Yongqin Ding Xuanming Chen Longlong 《Acta Geotechnica》2021,16(6):1849-1865
Acta Geotechnica - Snake can perfectly utilize its scales to move. Inspired by the snake scales, this study investigated the characteristics of the snake skin-inspired pile penetration process. Six... 相似文献
969.
Acta Geotechnica - Soils have a variety of mineral compositions. Although a number of thermal conductivity models have been developed for soils, few quantitatively investigated the effect of... 相似文献
970.
Changfeng Liu Zhiguang Zhou Guosheng Wang Chen Wu Hongying Li Shiwei Ma 《地学前缘(英文版)》2021,12(3):101103
The Xingmeng Orogenic Belt evolved through a long-lived orogeny involving multiple episodes of subduction and accretion. However, there is a debate on its tectonic evolution during the Late Paleozoic. Here, we report geochemical, geochronological, and isotopic data from strongly peraluminous granites and gabbro-diorites from the Sunidzuoqi–Xilinhot region. Zircon U–Pb ages suggest that the intrusive rocks were emplaced during the Early Carboniferous (333–322 Ma). The granites exhibit geochemical characteristics similar to S-type granites, with high SiO2 (72.34–76.53 wt.%), Al2O3 (12.45–14.65 wt.%), and A/CNK (1.07–1.16), but depleted Sr, Nb, and Ta contents. They exhibit positive εNd(t) and εHf(t) values (?0.3 to 2.8 and 2.7–5.7, respectively) and young Nd and Hf model ages (TDM2(Nd)=853–1110 Ma and TDM2(Hf)=975–1184 Ma), suggesting that they may be the partial melting products of heterogeneous sources with variable proportions of pelite, psammite, and metabasaltic rocks. The meta-gabbro-diorites from the Maihantaolegai pluton have low SiO2 (47.06–53.49 wt.%) and K2O (0.04–0.99 wt.%) contents, and demonstrate slight light rare earth element (REE) depletion in the chondrite-normalized REE diagrams. They have high zircon εHf(t) values (14.41–17.34) and young Hf model ages (TDM2(Hf)= 230–418 Ma), indicating a more depleted mantle source. The variations of the Sm/Yb and La/Sm ratios can thus be used to assess the melting degree of the mantle source from 5% to 20%, suggesting a quite shallow mantle melting zone. We propose that the petrogenesis and distribution of the strongly peraluminous granites and gabbro-diorites, as well as the tectonic architecture of the region, can be explained by a ridge subduction model. Based on these results, and previous studies, we suggest a southward ridge subduction model for the Sunidzuoqi–Xilinhot region. 相似文献