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   

Sunrise Hill unconformity: A newly discovered regional hiatus between Archaean granites and greenstones in the northeastern Pilbara Craton     

P. R. Dawes  R. H. Smithies  J. Centofanti  D. C. Podmore 《Australian Journal of Earth Sciences》2013,60(6):635-639

Contacts between Archaean granites and greenstones in the northeastern part of the Pilbara Craton have been described as intrusive and tectonic. New field observations in the Shay Gap region demonstrate that greenstones of the Gorge Creek Group unconformably overlie the Muccan and Warrawagine batholiths. Regionally, the unconformity is marked by a persistent but relatively thin basal clastic sequence, locally with a granite boulder conglomerate, overlain by ore‐bearing banded iron‐formation, fine‐grained clastic rocks and chert. The granite basement is dated at 3443 ± 6 Ma. The precise age of the hiatus is unknown but its maximum effect might have been the removal of a substantial thickness of Early to Middle Archaean strata.  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   

矿物热释氡找矿在某地含铀砂岩中的试验研究     

郑启荣  王有伦  常仕明 《铀矿地质》1988,(1)

该文探讨了矿物热释氡的氡来源较多的原因是每(μm)~3次生含铀矿物或眇岩中有数量巨大的——m×10~n(n>4,m、n为自然数)个的铀离子或晶胞。本文并介绍了取自4210砂岩铀矿床的坑道、钻孔及其矿区内的河流、陡壁的271个样品矿物热释氡的特征:热释氡晕范围较矿体宽约几十米,在平面、剖面上都有热释氡晕存在,产状与矿体一致,与地层和冲刷面有一定交角。表明热释氧晕受层位、岩相、构造等多种因素控制。这些特点,对指导技矿和分析矿床成因,无疑是有意义的。  相似文献   

Iron porphyrins in the Permian Kupferschiefer of the lower Rhine Basin, N.W. Germany     

C. B. Eckardt  M. Wolf  J. R. Maxwell 《Organic Geochemistry》1989,14(6)

Immature samples of the Permian Kupferschiefer from the Lower Rhine Basin in N.W. Germany were analysed for tetrapyrrole pigment type and abundance. The sediment, thought to have been deposited in a marine regime with enhanced salinity, was found to contain high concentrations of metalloporphyrins. The porphyrins are complexed to nickel (Ni) and oxovanadium (V=0), but high abundances of iron (Fe) porphyrins were also detected using UV/visible spectroscopy and mass spectrometry. The presence in the latter of series of aetioporphyrins, cycloalkanoporphyrins, di-cycloalkanoporphyrins and benz-cycloalkanoporphyrins was confirmed by accurate mass measurements; HPLC co-injection of deoxophylloerythroetioporphyrin (C₃₂ DPEP) with the demetallated iron porphyrins indicated its presence in the sediment as an iron complex. The study provides the first evidence for the occurrence of Fe porphyrins in geological samples other than coals and lignites, and reports the highest concentrations in sedimentary organic matter to date.  相似文献   

长江口泥沙的来源分析与数量计算的研究   总被引：3，自引：0，他引：3  

林承坤 《地理学报》1989,44(1):22-31

本文根据地学原理，建立了长江口泥沙的来源分析与数量计算的模式。定量分析了长江口泥沙来源，计算了泥沙的数量。通过验证表明沙量的计算值与验证值两者十分吻合。  相似文献   

攀西地区铁钛氧化物矿物的显微结构     

李朝晖  彭志忠 《地球科学》1988,(1)

本文用矿石显微镜及单晶X射线分析方法,研究了攀枝花—西昌地区铁钛氧化物矿物的显微结构共生组合特点、各出溶相间的关系和分布方位以及不同岩石和矿石显微结构共生组合上的差异。业已查明它们受岩浆旋回和岩石类型所控制。本文指出了磁铁矿-钛铁晶石固溶体显微出溶结构可能是拐点分解经调制结构后的终期产物。  相似文献   

云南安宁地区晚侏罗世含盐岩系的主要特点及沉积环境   总被引：2，自引：0，他引：2  

陈瑞君  朱井泉 《岩石学报》1993,9(1):94-104,T001

  相似文献   

游离氧化铁形态转化对红粘土工程性质的影响   总被引：6，自引：5，他引：6  

孔令伟  罗鸿禧 《岩土力学》1993,14(4):25-39

本文通过模拟环境中的有机质使游离氧化铁形态转化对典型红粘土工程性质的影响试验,系统地测试了游离氧化铁的形态分布与物性指标的关系。试验结果表明,在渍水条件下,游离氧化铁的形态转化对红粘土性质的影响不显著,但在渗水条件下,由于游离氧化铁的流失使得胶结作用减弱,它对红粘土工程性质的影响逐渐明显,其潜在的危害仍然是不容忽视的。  相似文献