Burial and exhumation of the Hoh Xil Basin,northern Tibetan Plateau: Constraints from detrital (U-Th)/He ages     

Jin-Gen Dai  Matthew Fox  David L. Shuster  Jeremy Hourigan  Xu Han  Ya-Lin Li  Cheng-Shan Wang 《Basin Research》2020,32(5):894-915

The uplift and associated exhumation of the Tibetan Plateau has been widely considered a key control of Cenozoic global cooling. The south-central parts of this plateau experienced rapid exhumation during the Cretaceous–Palaeocene periods. When and how the northern part was exhumed, however, remains controversial. The Hoh Xil Basin (HXB) is the largest late Cretaceous–Cenozoic sedimentary basin in the northern part, and it preserves the archives of the exhumation history. We present detrital apatite and zircon (U-Th)/He data from late Cretaceous–Cenozoic sedimentary rocks of the western and eastern HXB. These data, combined with regional geological constraints and interpreted with inverse and forward model of sediment deposition and burial reheating, suggest that the occurrence of ca. 4–2.7 km and ca. 4–2.3 km of vertical exhumation initiated at ca. 30–25 Ma and 40–35 Ma in the eastern and western HXB respectively. The initial differential exhumation of the eastern HXB and the western HXB might be controlled by the oblique subduction of the Qaidam block beneath the HXB. The initial exhumation timing in the northern Tibetan Plateau is younger than that in the south-central parts. This reveals an episodic exhumation of the Tibetan Plateau compared to models of synchronous Miocene exhumation of the entire plateau and the early Eocene exhumation of the northern Tibetan Plateau shortly after the India–Asia collision. One possible mechanism to account for outward growth is crustal shortening. A simple model of uplift and exhumation would predict a maximum of 0.8 km of surface uplift after upper crustal shortening during 30–27 Ma, which is insufficient to explain the high elevations currently observed. One way to increase elevation without changing exhumation rates and to decouple uplift from upper crustal shortening is through the combined effects of continental subduction, mantle lithosphere removal and magmatic inflation.  相似文献   

末次间冰期兰州黄土记录中的粘土矿物及其环境意义探讨   总被引：21，自引：2，他引：21  

师育新  戴雪荣 《海洋地质与第四纪地质》1997,17(1):87-94

本文研究了末次间冰肮分辨率兰州黄土（Ｓ１）２１个样口的粘土矿物，并与现代尘暴沉积物作了对比。研究结果表明，Ｓ１三个古土壤导春间所夹两个黄土层中的粘土矿物组合特征基本一致，以伊利石为主，其次为绿泥石和高岭石及少量伊／蒙间层矿物。粘土矿物的形成以碎屑成因为主，其一在剖面上的变化具有批示气候变化的意义。古土壤层中伊利石结晶度较黄土层中低，反映在气候温暖潮湿的条件下粘土矿物受到了不同和蔼的改造。粘土矿物总  相似文献   

海洋沉积物黏土矿物相对含量不同计算方法对比研究     

舒雨婷  刘志杰  余佳  孔敏  田先德  刘升发 《海洋通报》2019,(5):585-590

海洋沉积物黏土矿物相对含量计算存在多种计算方法,并不统一,限制了异源黏土矿物的整合和使用。文章选取了两种较为常见的计算方法,即Biscaye和国标中规定的计算方法,分别对东印度洋109个表层样品黏土矿物的相对百分含量进行计算,分析对比了两种方法计算结果之间的差异。结果显示,两种计算方法结果存在显著正相关,都能显示黏土矿物分布的变化趋势,4种黏土矿物相关系数由高到底分别为:蒙皂石0.986、伊利石0.974、绿泥石0.924、高岭石0.923。相对于Biscaye计算方法,国标计算方法会增加伊利石和高岭石的相对百分含量而降低蒙皂石和绿泥石的相对百分含量。两种计算方法黏土矿物的含量相关性较好,可以建立起相互数学转换关系式。但在不同的海区,由于矿物成因、结晶程度以及混层矿物的出现可能会使衍射峰形态发生改变,从而相关性系数和转换关系也会相应发生改变。  相似文献   

西藏罗布莎蛇绿岩铬铁矿中的超高压矿物和新矿物(综述)   总被引：32，自引：1，他引：32  

杨经绥  白文吉  方青松  戎合 《地球学报》2008,29(3):263-274

近十余年来的研究,在西藏雅鲁藏布江缝合带中的罗布莎蛇绿岩型铬铁矿中,发现可能来自深部(>300km深度)异常地幔矿物群.该矿物群中具有深部成因指示意义的矿物有:①呈斯石英假象的柯石英;②微粒金刚石和产在锇铱矿中的原位金刚石;③铬铁矿和饿铱矿巾发现硅尖晶石;④铬铁矿中发现硅金红石;⑤呈八面体假象的蛇纹石和绿泥石,并具有清晰的爆炸结构;⑥方铁矿和自然铁矿物组合.此外,罗布莎铬铁矿中有4个新矿物获批准,并在极地乌拉尔蛇绿岩铬铁矿中也发现了大最微粒金刚石和碳硅石等地幔超高压矿物.蛇绿岩铬铁矿中发现来自地幔深部的超高压矿物,提供了铬铁矿可能深部成因的重要信息,该发现有可能改变传统的蛇绿岩铬铁矿的形成于俯冲带上的浅部环境(<50 km深度)的认识以及蛇绿岩成因的概念.  相似文献   

柴达木盆地烃蚀变矿物高光谱遥感识别研究   总被引：2，自引：0，他引：2  

胡畔  田庆久  闫柏琨 《国土资源遥感》2009,(2):54-61

高光谱遥感识别烃蚀变矿物可用于探测油气烃类微渗漏和定位地下油气藏.以有天然气分布的柴达木盆地东部三湖地区为研究区,对Hyperion高光谱数据进行重采样处理,克服了目标识别矿物不明显和传感器低信噪比的影响.通过确定烃蚀变矿物高光谱遥感探测的指示标志,采用线性光谱(SAM)拟合与光谱匹配(SAM)相结合的方法确定了影像端元对应的矿物组分.识别结果表明,合理缩减影像波段数和确定影像端元的方法,能有效提高烃蚀变矿物的高光谱遥感识别精度.  相似文献   

Phosphate mineral accumulation in lake sediment to form a secondary phosphate source: A case study in lake sediment around Eppawala Phosphate Deposit (EPD) in Sri Lanka   总被引：1，自引：0，他引：1  

Nimila Dushyantha  Nalin Ratnayake  Hemalal Panagoda  Chulantha Jayawardena  Amila Sandaruwan Ratnayake 《国际泥沙研究》2021,36(4):532-541

Global phosphorus scarcity will result in significant consequences for future food security with the depletion of current phosphate reserves.Therefore,exploration of new phosphorus sources is essential to address future phosphorus scarcity.The current study investigated the geochemical potential of lake sediment around the Eppawala Phosphate Deposit(EPD)in Sri Lanka to be used as a low-grade phosphorus source for agricultural purposes.Jaya-Ganga is a man-made water canal that drains through the EPD feeding three lakes,namely,upstream Ihalahalmilla Lake and Koon Lake,and downstream Kiralogama Lake with respect to the EPD.Three cores(cores A,B,and C)were collected from the above three lakes and major oxides and minerals distributions along the cores were analyzed.Notable high enrichment of phosphorus pentoxide(P2O5)content and high P2O5 solubility values were measured in the top 60 cm sediment layer in Core B and throughout the Core C compared to the Core A.This high enrichment of P2O5 content in the same sediment columns were confirmed by the comparison with the Upper Continental Crust(UCC)values and literature survey.According to the X-ray Diffraction(XRD)results,phosphate minerals,such as fluorapatite,crandallite,and millisite were abundantly found in the same sediment columns.Therefore,these phosphate minerals can be considered as pathfinding minerals for soluble phosphates in sediment cores.Thus,sediment with high P2O5 content and high solubility in downstream Kiralogama Lake showed the potential for application of these sediments as a direct phosphate source in agricultural purposes.Furthermore,the current study has introduced a new area of interest,i.e.,soil and sediments around major phosphate deposits,for the exploration of new phosphate sources to meet future phosphorus demand.  相似文献   

CONSONORM_HG: a new method of norm calculation for mid‐ to high‐grade metamorphic rocks          下载免费PDF全文

L. Mathieu  S. Trépanier  R. Daigneault 《Journal of Metamorphic Geology》2016,34(1):1-15

  相似文献   

Origin of sandplains in Western Australia: A review of the debate and some recent findings     

D. Newsome 《Australian Journal of Earth Sciences》2013,60(4):695-706

Views on the origin of sandplains in Western Australia remain controversial with debate focusing around three different models of formation. These are in situ, aeolian and in situ formation with local remobilisation by wind or colluvial transport. The only recent work on the subject to date espouses a dominantly aeolian origin. New work from a detailed study on the Victoria Plateau is described and demonstrates the applicability of utilising a range of evidence in understanding the origin of sandplains in Western Australia. Field investigations show a strong association of sandplain with sandstone and an absence of sand on non‐arenaceous geology in similar and adjacent topographic settings. Grainsize, mineral magnetic analysis and heavy‐mineral spectra show the Victoria Plateau to be a heterogeneous body of sand. These findings coupled with a lack of internal sedimentary structures are not consistent with an aeolian origin for the sandplain. Furthermore, scanning electron microscopy, grainsize and heavy minerals also demonstrate a clear link between bedrock and overlying sandplain. These data support the hypothesis that Western Australian sandplains are mostly the product of in situ weathering. Such findings question whether the origin of sandplains can be satisfactorily deduced without such a range of data.  相似文献   

Trace‐element signatures of apatites in granitoids from the Mt Isa Inlier,northwestern Queensland     

E. A. Belousova  S. Walters  W. L. Griffin  S. Y. O'Reilly 《Australian Journal of Earth Sciences》2013,60(4):603-619

The concentrations of trace elements in apatite from granitoid rocks of the Mt Isa Inlier have been investigated using the laser‐ablation inductively coupled plasma‐mass spectrometry (ICP‐MS) microprobe. The results indicate that the distribution of trace elements (especially rare‐earth elements (REE), Sr, Y, Mn and Th) in apatite strongly reflects the chemical characteristics of the parental rock. The variations in the trace‐element concentrations of apatite are correlated with parameters such as the SiO₂ content, oxidation state of iron, total alkalis and the aluminium saturation index (ASI). The relative enrichment of Y, HREE and Mn and the relative depletion of Sr in the apatites studied reflect the degree of fractionation of the host granite. Apatites from strongly oxidised plutons tend to have higher concentrations of LREE relative to MREE. Manganese concentrations are higher in apatite from reduced granitoids because Mn²⁺substitutes directly for Ca²⁺. The La/Ce ratio of apatite is well‐correlated with the whole‐rock K²O and Na²O contents, as well as with the oxidation state and ASI. Because apatite trace‐element composition reflects the chemistry of the whole rock, it can be a useful indicator mineral for the recognition of mineralised granite suites, where particular mineralisation styles are associated with granitoids that have specific geochemical fingerprints.  相似文献   

Silurian and Devonian systems     

Maxwell R. Banks  E. D. Gill  K. L. Burns 《Australian Journal of Earth Sciences》2013,60(2):177-187

The Ediacara mineral field is situated 30 km W of Beltana on the western margins of the Flinders Ranges, South Australia, and consists of silver‐lead and copper deposits in lower Cambrian carbonate rocks that contain anomalous base‐metal contents throughout the Adelaide Geosyncline. The lower Cambrian rocks, which consist of the basal Parachilna Formation and overlying Ajax Limestone, rest disconformably on the Precambrian, and at Ediacara occupy a shallow N‐S elongate syncline near the hinge zone of the Adelaide Geosyncline. The main primary ore minerals of the silver‐lead mineralization are galena and pyrite, with very minor chalcopyrite and sphalerite, and rare tetrahedrite and pearceite. The gangue consists mainly of silica (both chalcedony and quartz), with minor dolomite and rare barite. The mineralization is stratabound and occurs in conformable zones, the lowest of which commences about 30–50 m above the base of the Cambrian sequence. The host to the silver‐lead mineralization, the Ajax Limestone, can be subdivided into three units which represent a set of lithologies, structures and organic traces indicative of a shallow near‐shore carbonate environment. The silver‐lead mineralization is mainly present in sandy and laminated dolomites which were deposited in an environment ranging from sub‐tidal to bar and channel and tidal flat, respectively. Four types of mineralization have been recognized; disseminated sulphides of syngenetic and/or diagenetic origin and epigenetic concentrations along stylolites, in veins and as breccia fillings. Post‐depositional solution activity has affected a large proportion of the carbonate sequence. The effects of this activity range from stylolites through stylobreccias to solution collapse breccias. The epigenetic concentrations of mineralizations have apparently been formed by the remobilization of the disseminated sulphides during solution activity. The ore and gangue minerals of the epigenetic mineralization display both euhedral forms and distinct colloform banding, and framboidal textures have also been observed in both pyrite and galena. There is evidence of repeated episodic precipitation and no simple paragenetic sequence can be recognized. Fluid inclusions in silica and dolomite associated with the epigenetic mineralization have homogenization temperatures of 159 to 199°C and freezing temperatures that indicate the fluids to be saline brines containing NaCl with CaCl₂ and/or MgCl₂. Sulphur isotope analyses show a range of 8³⁴S values from ‐12.5 to +8.6 per mil, with no evidence of significant differences between the four types of mineralization. The data suggest deposition of the disseminated sulphides as a result of biological reduction of seawater sulphate in a system partially open with respect to sulphate supply. Subsequent remobilization of sulphides apparently involved little or no sulphur isotope fractionation. The Ediacara silver‐lead deposits have many features in common with Mississippi Valley‐type lead‐zinc deposits and appear to have similarities in terms of genesis, in that the epigenetic mineralization has been formed as a result of post‐depositional solution activity during diagenesis in a sedimentary basin. The scale of transport of the metals deposited as the epigenetic mineralization at Ediacara appears, however, to have been very much less than that of the metals in other Mississippi Valley‐type deposits.  相似文献