青藏高原东北部残积母质土壤发育过程研究——以青海湖北部宁夏剖面为例          下载免费PDF全文

谢丽倩  鄂崇毅  赵霞  李萍  张晶  孙满平  先巴吉 《干旱区地理》2022,45(4):1146-1154

残积母质是青海湖地区重要的成土母质之一,目前对高原残积母质土壤的研究相对匮乏,特别是其形成发育的年代尚不明晰,限制了对高原残积母质土壤演变过程的认识及对区域气候环境演变的理解。为探究青藏高原东北部残积母质土壤的发育过程及其发育模式,以青海湖北部宁夏（NX）剖面作为研究对象,通过光释光（Optically stimulated luminescence,OSL）测年获得残积母质土壤发育年代,采用化学蚀变指数（Chemical index of alteration,CIA）、Rb/Sr和粉黏比等探究土壤发育程度,对比青海湖地区河湖相沉积和黄土的Zr/Nb、K₂O/Al₂O₃和TiO₂/Al₂O₃分析其物源。结果表明：NX土壤剖面在早全新世以来发育,其年代结果集中在10.02~8.67 ka,成土母质发育时间与流域内风沙强烈活动时期基本一致,为干暖气候背景下的产物;通过物源对比分析,NX剖面底部母质为母岩就地风化而成,上部为风尘加积发育,发育模式为混合母质风尘加积型;剖面整体处于弱化学风化阶段,土壤发育程度较弱。  相似文献   

安徽省江淮流域土壤地球化学基准值与背景值研究   总被引：13，自引：0，他引：13       下载免费PDF全文

陈兴仁陈富荣  贾十军陈永宁 《中国地质》2012,39(2):302-310

基于安徽省江淮流域多目标区域地球化学调查数据资料,统计获得了表层和深层土壤地球化学基准值、背景值及相应的地球化学参数,为研究区生态环境评价及相关学科研究提供了基础。研究表明,成土母质类型对土壤元素地球化学基准值影响显著,表层土壤化学组成表现出既对深层土壤具有一定的继承性,又在表生作用下发生某些变化:表层土壤中迁移活动性强的元素和人为扰动污染的元素明显不同于深层土壤;随着地理空间位置的变化,同类成土母质形成环境、成因来源的差异导致其化学组成的空间变异,造成不同地区同类成土母质地球化学基准值有所不同。因此,土壤地球化学基准值研究应更多地考虑地质背景、物质来源等因素的影响。  相似文献   

内蒙古兴和县曹四夭钼矿床地球化学特征及成矿模型探讨   总被引：6，自引：1，他引：5  

李香资  班宜红  权知心  瓮纪昌  王卫东 《华北地质》2012,(1):39-46

内蒙古兴和县曹四夭钼矿是河南省地勘二院2010年新发现的一个特大型钼矿,就目前工作程度,预计钼金属量超过200万吨.通过对该钼矿床地球化学特征的分析研究,揭示了利用岩屑化探测量作为有效手段发现并推断斑岩型钼矿床规模的基本思路.该区通常主要钼矿体地表露头被严格限制在Mo、 W、 Cu、 Pb、 Zn、 As、 Sb综合异常中心部位,成矿母岩花岗斑岩是钼矿体主要控矿因素,也是重要的找矿标志,元素组合分类和水平分带特征为判断矿体前景指明了方向.(Mo+W+Zn)/(Cu+As+Sb)三元素加权比值图不仅揭示了钼矿体地表剥蚀水平,而且指示了钼矿体边缘与物化探等值线梯度带的对应特征,初步建立了曹四夭钼矿床的成矿地球化学模型  相似文献   

The Almahata Sitta polymict breccia and the late accretion of asteroid 2008 TC₃     

Marian Horstmann  Addi Bischoff 《Chemie der Erde / Geochemistry》2014

On October 7, 2008, a small asteroid named 2008 TC₃ was detected in space about 19 h prior to its impact on Earth. Numerous world-wide observations of the object while still in space allowed a very precise determination of its impact area: the Nubian Desert of northern Sudan, Africa. The asteroid had a pre-atmospheric diameter of ∼4 m; its weight is reported with values between ∼8 and 83 t, and the bulk density with ∼2–3 g/cm³, translating into a bulk porosity in the range of ∼20–50%. Several dedicated field campaigns in the predicted strewn field resulted in the recovery of more than 700 (monolithological) meteorite fragments with a total weight of ∼10.5 kg. These meteorites were collectively named “Almahata Sitta”, after the nearby train station 6, and initially classified as an anomalous polymict ureilite. Further work, however, showed that Almahata Sitta is not only a ureilite but a complex polymict breccia containing chemically and texturally highly variable meteorite fragments, including different ureilites, a ureilite-related andesite, metal-sulfide assemblages related to ureilites, and various chondrite classes (enstatite, ordinary, carbonaceous, Rumuruti-like). It was shown that that chondrites and ureilites derive from one parent body, i.e., asteroid 2008 TC₃, making this object, in combination with the remotely sensed physical parameters, a loosely aggregated, rubble-pile-like object. Detailed examinations have been conducted and mineral-chemical data for 110 samples have been collected, but more work on the remaining samples is mandatory.  相似文献   

平朔矿区安太堡煤矿9^#煤的有机地球化学特征     

王双杰  王金喜  李世龙 《中国煤炭地质》2014,(12):20-23

9^#煤是安太堡煤矿的主要可采煤层之一,宏观煤岩类型为半暗型煤。通过对煤中可溶有机质成分特征及饱和烃、芳香烃中各项生物指标化合物含量进行分析,得出：（1）样品中较高的芘含量反映煤样中的成煤母质中陆源高等植物占优势;（2）OEP指数和芳香烃中MPI指数均呈现低值,指示有机质的成熟度较低;（3）Pr/Ph值变化较大,氧芴含量稍高,指示成煤环境海侵频繁,氧化还原沉积环境交替。  相似文献   

Geochemistry and zircon U-Pb ages of the Oligocene sediments in the Baiyun Sag,Zhujiang River Mouth Basin     

Rui Sun  Ming Ma  Kai Zhong  Xiayang Wang  Zhao Zhao  Shuai Guo  Xingzong Yao  Gongcheng Zhang 《海洋学报(英文版)》2021,40(2):123-135

In this study, element geochemistry and zircon chronology are used to analyze the Oligocene sediments in the Baiyun Sag, Zhujiang River Mouth Basin. The experimental results are discussed with respect to weathering conditions, parent rock lithologies, and provenances. The chemical index of alteration and the chemical index of weathering values of mudstone samples from the lower Oligocene Enping Formation indicate that clastic particles in the study area underwent moderate weathering. Mudstone samples exhibit relatively enriched light rare earth elements and depleted heavy rare earth elements, "V"-shaped negative Eu anomalies, and negligible Ce anomalies. The rare earth element distribution curves are obviously right-inclined, with shapes and contents similar to those of post-Archean Australian shale and upper continental crust, indicating that the samples originated from acid rocks in the upper crust. The Hf-La/Th and La/Sc-Co/Th diagrams show this same origin for the sediments in the study area. For the samples from the upper Enping deltas, the overall age spectrum shows four major age peaks ca. 59–68 Ma, 98–136 Ma, 153–168 Ma and 239–260 Ma. For the Zhuhai Formation samples,the overall age spectrum shows three major age peaks ca. 149 Ma, 252 Ma and 380 Ma. The detrital zircon shapes and U-Pb ages reveal that during Oligocene sedimentation, the sediments on the northwestern margin of the Baiyun Sag were supplied jointly from two provenances: Precambrian-Paleozoic metamorphic rocks in the extrabasinal South China fold zone and Mesozoic volcanic rocks in the intrabasinal Panyu Low Uplift, and the former supply became stronger through time. Thus, the provenance of the Oligocene deltas experienced a transition from an early proximal intrabasinal source to a late distal extrabasinal source.  相似文献   

Grain-size Analysis of Surface Material Under Wind Erosion Using the Effective Surface Concept     

Lawrence W. Martz  Long Li 《地球表面变化过程与地形》1997,22(1):19-29

The grain mobility and roughness of a surface exposed to wind are dependent on the grain size of the surface particles. This paper deals with the temporal variation in the grain size of surface material using an analytical method based on the effective surface concept. The analysis of grain size data obtained from a wind tunnel experiment indicated that, above the threshold wind friction velocity for all surface particles, the grain-size distribution of surface particles was very similar to that of the parent material over a time period of 10 to 15 minutes. However, the mean grain size of surface particles apparently decreased over the initial time period of 2 to 3 minutes. We therefore confirm earlier studies that on a non-uniform grain bed a larger particle could be more mobile than a smaller particle if the wind friction velocity was higher than the threshold for the larger particle. However, this does not imply that the largest particle is most mobile due to the non-linear dynamics of aeolian sediment transport processes. © 1997 by John Wiley & Sons, Ltd.  相似文献   

人工养殖条件下多齿围沙蚕亲体培育和繁殖生物学的初步研究   总被引：2，自引：0，他引：2       下载免费PDF全文

杜荣斌  刘红梅  郑家声  冯俊荣  刘立明  王勇强 《海洋科学》2009,33(11):37-43

通过生态学及组织学方法对人工养殖条件下多齿围沙蚕(Perinereis nuntia Savigny)亲体培育条件及繁殖生物学进行了研究.结果表明,多齿围沙蚕雌雄异体,非成熟季节外观上无法辨别雌雄,性成熟时,雌(异沙蚕体)灰绿色,雄(异沙蚕体)红白色.生殖细胞起源于体腔膜上皮,不久就释放到体腔中,在体腔内卵原细胞和精原细胞http://ebook/成都,今夜请将我遗忘/index.htm分裂增殖形成卵原细胞群和精原细胞群,体腔中充满了外形不规则或近圆形的滋养细胞,细胞内可见嗜伊红颗粒,滋养细胞之间可见发达的微血管.卵原细胞群不断增殖发育,至初级卵母细胞后游离至体腔中继续发育为次级卵母细胞和成熟卵子;精原细胞群形成精子合胞体(syncytium),各级精母细胞在合胞体内发育,直至形成成熟精子时才分散游离.水温18℃以上,多齿围沙蚕的生长体经培育才可能形成异沙蚕体.特别是在经历了一定的低温期后,再提高温度可以有效的促进异沙蚕体形成.胚胎发育的适宜温度为18～25℃;适宜盐度为25～32.胚胎发育过程经历卵裂期、囊胚期、原肠期、担轮幼虫期、后担轮幼虫期、膜内游毛幼虫期等阶段,在水温25℃、盐度30条件下,从受精至孵出3刚节幼虫约需65 h.3刚节游毛幼虫至10刚节幼体约需28 d.  相似文献   

珠母贝亲贝催熟培育和催产技术的研究   总被引：3，自引：0，他引：3       下载免费PDF全文

黄海立  符韶  邓陈茂  刘志刚 《海洋科学》2009,33(10):1-4

对不同来源珠母贝(Pinctada margaritifera)亲贝分别进行海上浅吊疏养促熟和室外水泥池人工催熟培育,且采用阴干、藻液、温度、低盐度刺激和异性产物诱导亲贝排放精卵,比较不同方法、不同来源亲贝性腺发育及亲贝开始排放时间、排放率、受精率和幼虫畸形率情况.结果表明,室外水泥池人工催熟法亲贝性腺成熟度比浅吊疏养促熟法好、死亡率低;相同培育方法,北部湾亲贝比海南亲贝性腺成熟快,但死亡率高;阴干刺激3 h+藻液刺激1 h+异性产物诱导,性腺达到第四期(排放期)的亲贝才排放,且排放的性细胞成熟度好,受精率高,幼虫畸形率低.  相似文献