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Sequence‐stratigraphic interpretations of the 4200 m‐thick Palaeoproterozoic (1700–1650 Ma) Mt Isa Group and underlying Surprise Creek Formation identify three unconformity‐bounded packages termed the Prize, Gun and Loretta Supersequences. Siliciclastic rocks of the Surprise Creek Formation and Warrina Park Quartzite comprise the Prize Supersequence. Rapid facies changes from proximal, conglomeratic fluvial packages to distal, fine‐grained and deep‐water, rhythmites characterise this supersequence. Conglomeratic intervals in the Mt Isa area reflect syndepositional movement along basin‐margin faults during the period of supersequence initiation. A major unconformity, which extends over a period of about 25 million years, separates the Gun and Prize Supersequences. In the Leichhardt River Fault Trough uplift and incision of Prize sedimentary rocks coincided with emplacement of the Sybella Granite (1671±8 Ma) and Carters Bore Rhyolite (1678±2 Ma) and the removal of an unknown thickness of Prize Supersequence section. Deep‐water, turbiditic rhythmites of the Mt Isa Group dominated the Gun and Loretta Supersequences. Tempestites are present over discrete intervals and represent times of relative shallowing. High accommodation and sedimentation rates at the base of the Gun Supersequence resulted in the deposition of transgressive nearshore facies (uppermost Warrina Park Quartzite) overlain by a thick interval of deep‐water, siltstone‐mudstone rhythmites of the Moondarra Siltstone and Breakaway Shale. With declining rates of siliciclastic sedimentation and shallowing of the succession, calcareous sediments of the Native Bee Siltstone prograded over the deeper water deposits. Two third‐order sequences, Gun 1 and 2, characterise these lower parts of the Gun Supersequence. An increase in accommodation rates near the top of the Native Bee Siltstone in Gun 3 time, resulted in a return to deep‐water sedimentation with deposition of dolomitic rhythmites of the Urquhart Shale and Spear Siltstone. The Pb–Zn–Ag ore‐hosting interval of the Urquhart Shale is interpreted to occur in progradational highstand deposits of the Gun 3 Sequence. In the Leichhardt River Fault Trough the Loretta Supersequence boundary forms a correlative conformity. Coarser grained and thicker bedded sediments of the Kennedy Siltstone comprise lowstand deposits at the base of this cycle. These sediments fine up into the transgressive, deep‐water, siliciclastic facies of the Magazine Shale, which in turn are truncated against the Mt Isa Fault. 相似文献
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Aitkenhead Isabella Kuleshov Yuriy Watkins Andrew B. Bhardwaj Jessica Asghari Atifa 《Natural Hazards》2021,109(2):1425-1455
Natural Hazards - The Northern Murray–Darling Basin (MDB) is a key Australian agricultural region requiring efficient Agricultural Drought Management (ADM), focused on resilience. Although a... 相似文献
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A high-resolution dataset of trace element concentrations is presented for the Murray–Darling Basin, Australia, Australia’s most important river system. The data were obtained by solution quadrupole ICP-MS resulting in concentrations for 44 elements. Of these, 21 were determined with a long-term external precision of better than 1% and a further 13 at a precision better than 2%. Trace element maps for the surface sediments constructed from such high precision data reveal small but coherent variations in the four major sub-catchments of the basin, even in ratios of elements with very similar geochemical behaviour, such as Y/Ho, Nb/Ta and Zr/Hf. The origin of these chemical fingerprints of drainage systems are discussed in terms of the geochemical character of the upper continental crust. The potential of trace element maps for palaeo-environmental and climatic reconstruction is then illustrated. First, a sample of dust collected in a trap located in the far southeastern corner of the study area is used to pinpoint the location of the dust source. Next the fine-scale change in down-stream alluvial sediment chemistry is analysed to estimate the importance of sediment contribution from tributaries with a view to reconstructing river flow dynamics. Finally, the chemistry of dune sediments is compared with surrounding floodplain alluvium to estimate relative age of deposition. These examples demonstrate that in low-elevation river systems, such as the Murray–Darling Basin, extended trace element maps of sediment offer substantially more applications than radiogenic isotope data alone. 相似文献
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《Applied Geochemistry》2001,16(4):475-488
The usefulness of stable isotopes of dissolved SO4 (δ34S and δ18O) to study recharge processes and to identify areas of significant inter-aquifer mixing was evaluated in a large, semi-arid groundwater basin in south-eastern Australia (the Murray Basin). The distinct isotopic signatures in the oxidizing unconfined Murray Group Aquifer and the deeper reducing Renmark Group confined aquifer may be more sensitive than conventional chemical tracers in establishing aquifer connections. δ34S values in the unconfined Murray Group Aquifer in the south and central part of the study area decrease along the hydraulic gradient from 20.8 to 0.3‰. The concomitant increasing SO4/Cl ratios, as well as relatively low δ18OSO4 values, suggest that vertical input of biogenically derived SO4 via diffuse recharge is the predominant source of dissolved SO4 to the aquifer. Further along the hydraulic gradient towards the discharge area near the River Murray, δ34S values in the unconfined Murray Group Aquifer increase, and SO4/Cl ratios decrease, due to upward leakage of waters from the confined Renmark Group Aquifer which has a distinctly low SO4/Cl and high δ34S (14.9–56.4‰). Relatively positive δ34S and δ18OSO4 values, and low SO4/Cl in the Renmark Group Aquifer is typical of SO4 removal by bacterial reduction. The S isotope fractionation between SO4 and HS− of ∼24‰ estimated for the confined aquifer is similar to the experimentally determined chemical fractionation factor for the reduction process but much lower than the equilibrium fractionation (∼70‰) even though the confined groundwater residence time is >300 Ka years. Mapping the spatial distribution of δ34S and SO4/Cl of the unconfined Murray Group Aquifer provides an indicative tool for identifying the approximate extent of mixing, however the poorly defined end-member isotopic signatures precludes quantitative estimates of mixing fractions. 相似文献
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以泥盆系占优势的南秦岭成矿带中存在有重要的Ｐｂ－Ｚｎ－Ａｇ，Ａｕ，Ｈｇ－Ｓｂ及Ｃｕ矿床。它们形成中晚古生带扬子地块北部被动大陆边缘的沉积盆地演化与造山期中，成矿系列显示出时间与空间的演化特征，构在了一个热水沉积成矿系列，成矿发生于一个热旋回中，各种矿化有相似的物源，每一种地质事件都有特定的金属富集及富集在型和大型矿床是该地区构造－岩浆变质变形作用的最终产物。 相似文献
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应用ＩＣＰ－ＭＳ法测定了岩石中的痕量Ｎｂ、Ｔａ、Ｚｒ、Ｈｆ、Ｔｈ、Ｕ，给出了检出限，并对酸溶和碱熔两种制样方法进行了对比实验。 相似文献
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Marie-PierreAubry WilliamA.Berggren JohnVanCouvering BrianMcGowran BradPillans FritsHilgen 《《幕》》2005,28(2):118-120
The long controversy over the term ‘Quaternary‘ as a chronostratigraphic unit may be reaching an apotheosis, judging from recent papers (Pillans and Naish, 2004; Gibbard et al., 2005; and referencest herein). The debate is no longer centered on whether there should be a place in the geological time scale for a unit termed ‘Quaternary‘-despite its dubious past, it cannot be denied that a large body of earth-historical research is strongly identified with this term. The challenge now concerns an appropriate rank and definition of Quaternary with regard to other chronostratigraphic units. Several options have been proposed (Pillans and Naish, 2004), and Gibbard et al. (2005) encourage a debate on these before decision is reached. In this brief note, we describe an arrangement not previously considered that seems advantageous. It is instructive, however, to first review the Pleistocene Series and Neogene System, the two units that are directly affected by introduction of the Quaternary into the chronostratigraphic hierarchy. 相似文献
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大陆漂移, 板块构造, 地质力学 总被引：2，自引：0，他引：2
本文简要地介绍了魏格纳大陆漂移说的主要内容及其提出的依据; 论述了在大陆漂移说的基础上, 由于海洋地质地球物理调查发现了大洋中脊、洋底扩张, 解释了大陆张裂的机制, 并建立了全球板块构造理论, 形成现代地学思想的革命; 李四光在大陆漂移说提出的同时已在积极地探讨和论述大陆地壳水平运动问题, 并结合中国大陆实际, 发展了陆内碰撞变形理论, 即包括全球大陆构造体系在内的地质力学理论和方法。他强调地质力学是一支脚站在地质上, 另一支脚站在力学上来研究地壳运动和变形现象。后来更扩大了其在资源、环境方面的应用。文章对魏格纳大陆漂移说、全球板块构造理论及地质力学三者的关系做了深入探讨, 论述了李四光地质力学理论方法的现代意义、超前意义, 提出要重视和发扬李四光留给中国人民的宝贵遗产, 建议深入学习李四光的著述, 结合地质调查新成果去丰富它和发展它。 相似文献
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We collected groundwaters in and around a large (313 Mt at 1.08% Cu and 0.3% cutoff) undisturbed porphyry copper deposit (Spence) in the hyperarid Atacama Desert of northern Chile, which is buried beneath 30–180 m of Miocene piedmont gravels. Groundwaters within and down-flow of the Spence deposit have elevated Se (up to 800 μg/l), Re (up to 31 μg/l), Mo (up to 475 μg/l) and As (up to 278 μg/l) concentrations compared to up-flow waters (interpreted to represent regional groundwater flow). In contrast, Cu is only elevated (up to 2036 μg/l) in groundwaters recovered from within the deposit; Cu concentrations are low down gradient of the deposit. The differential behavior of the metals/metalloids occurs because the former group dissolves as anions, enhancing their mobility, whereas the base metals dissolve as cations and are lost from solution most likely through adsorption to clay surface exchange sites and through formation of secondary copper chlorides, carbonates, and oxides. Most groundwaters within and down-flow of the deposit have Eh–pH values around the FeII/FeIII phase boundary, limiting the impact of Fe-oxyhydroxides on oxyanions mobility. Se, Re, Mo, and As are all mobile (with filtered/unfiltered samples ～ 1) to the limit of sampling 2 km down gradient from the deposit. The increase in ore-related metals, metalloids, and sulfate and decrease in sulfate–S isotope ratios (from values similar to regional salars, + 4 to + 8‰ δ34SCDT to lower values closer to hypogene sulfides, + 1 to + 4‰ δ34SCDT) is consistent with active water–rock reactions between saline groundwaters and the Spence deposit. It is likely that hypogene and/or supergene sulfides are being oxidized under the present groundwater conditions and mineral saturation calculations suggest that secondary copper minerals (antlerite, atacamite, malachite) may also be actively forming, suggesting that supergene and exotic copper mineralization is possible even under the present hyperarid climate of the Atacama Desert. 相似文献
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201富铀矿床氢,氧,碳,硫,铅同位素研究 总被引：5，自引：0，他引：5
产于花岗岩中的２０１铀矿床是我国花岗岩型铀矿富矿之一。本文通过氢、氧、碳、硫、铅同位素组成的研究，探讨成矿溶液和成矿物质的来源，推测成矿环境。研究结果表明，该矿床成矿流体是以大气降水为主，主要成矿物质来自前燕山期花岗岩体，可能部分来自下部地壳，成矿作用是在较稳定的物化条件下进行。 相似文献
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以硅粉的1％，2％－10％（wB）将Nb,Mo,Ti,Ta,W等5种金属粉掺入硅粉中，用液硅渗透法（LSP）制务出系列掺杂硅化石墨样品，这对些样品抗折，抗拉强测试结果：Nb(6%)－硅化石墨性能最优，抗拉强度提高了20％－27％，Mo(1%),Mo(5%)掺杂效果次之，而Ti(7%),Ta(3%),W(7%)等的杂反使材料强度降低。扫描电子显微镜（SEM）分析显示：Nb(6%）掺杂使抗担强增强的原因在于，新的铌与碳的间隙化合物相的生成，减小了硅化石墨显微结构的尺寸，且使材料外层及内核结构均匀，致密，统一，因而能有效分散应力集中，缓冲裂纹扩张，增大承载截面，从而提高材料力学性能。相反Ti(7%),Ta(3%)等掺杂后，尽管使材料外层结构致密，但内部结构疏松，晶粒，孔隙尺寸不大小不一，形态各异，外结构极不统一，导致材料性能下降。 相似文献
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