胶东西北部地区现代河流砂金的聚集规律及水动力学解释     

周江羽  刘常青 《沉积学报》1997,15(1):123-127

研究区位于胶东半岛西北部，具有丰富的岩金和砂金资源，是我国目前重要的黄金产地。作者应用沉积学和水动学的理论和方法，重点研究了该地区现代河流的沉积学特征、砂金聚集规律及其形成的水动力条件，认为河流砂金的聚集是一个与机械成矿作用密切相关的动态过程，与特定的河流水动力条件有关，其中横向环境的底流对于形成河谷台阶状缓坡倾斜面及砂金聚集具有重要意义。  相似文献   

云南红河三家河地区第四纪地质及其与砂金成矿关系研究     

陈军胜 《地质与勘探》1997,33(5):10-15

热带，亚热带气候，强烈切割的三家河地区的第四纪地质作用对三家河流域内砂金矿的形成具有直接意义，其砂金矿床类型，富集规律，成矿期次及矿床的工业意义均是第四纪地质作用的体现。  相似文献   

浅谈冲积型砂金矿床成矿模式——以陕西月河砂金矿床为例   总被引：2，自引：0，他引：2  

邓金利 《陕西地质》1993,(2)

本文通过对砂金矿床形成过程的分析认为:在地壳局部下沉过程中,砂金在水等强应力作用下,与砾石、砂一起进入沉积盆地,形成砂金的中间储存体;随着地壳的间歇性上升,在蛇曲河流的作用下由于砂金与砾石的运动规律相仿,故和砾面一起被保留在河流冲刷面上的河床滞留砾石沉积中。当地壳多次间歇性上升后,使砂金中间储存体中分散的砂金集中富集在河床滞留砾石层中,从而形成砂金矿床。  相似文献   

中国稀土矿床成因类型   总被引：3，自引：0，他引：3       下载免费PDF全文

张培善 《地质科学》1989,(1):26-32

稀土矿床和稀土矿化地区在地质空间和地质时间的分布方面各有规律。空间上既分布于稳定地区(地台和准地台),亦分布于活动地区(地槽和褶皱系)。在地质时代方面,各造山运动和岩浆活动期都能够成矿,尤以海西期和燕山期矿化规模大,面积广。根据成矿条件,将稀土矿床划分为十种成因类型,即:1)花岗岩、碱性花岗岩、花岗闪长岩、钠长石化花岗岩型;2)碱性岩型;3)火成碳酸岩型;4)矽卡岩型;5)伟晶岩型;6)变质岩和沉积变质碳酸盐岩石型;7)热液交代和热液脉型;8)沉积岩型;9)稀土砂矿型;10)花岗岩类风化壳型。  相似文献   

Evolution of Cretaceous–Cenozoic quartz pebble conglomerate gold placers during basin formation and inversion, southern New Zealand     

J.H. Youngson  D. Craw  D.M. Falconer 《Ore Geology Reviews》2006,28(4):451

Numerous auriferous fluvial quartz pebble conglomerates (QPCs) are present within the Late Cretaceous–Recent sedimentary sequence in southern New Zealand. The QPCs formed in low-relief settings before, during, and after regional marine transgression, in alluvial fan and a variety of fluvial and near-shore depositional settings: In particular, during slow thermal subsidence associated with Late Cretaceous–early Cenozoic rifting, and during the early stages of orogenic uplift following mid Cenozoic marine regression. QPC maturity characteristics are complex and vary with sediment transport and recycling history, stratigraphic proximity to the transgressive Waipounamu Erosion Surface, and the amount of first-cycle detritus incorporated during recycling. For pre-marine QPCs, the amount of first cycle detritus varies with tectonic intensity and proximity of the depositional setting to remnant Cretaceous topography. For post-marine QPCs, it varies with tectonic intensity and proximity to Late Cenozoic uplift of basement ranges.QPCs do not form during a single bedrock erosion–sediment deposition cycle: Non-oxidised and/or oxidized groundwater alteration (kaolinisation) of labile minerals in immature sediment and the upper part of underlying basement, and repeated sedimentary recycling, are fundamental processes of QPC formation regardless of the tectonic or sedimentary settings. Altered immature rock disaggregates easily upon erosion, and alteration clays are winnowed to leave quartz-rich residues containing resistant heavy minerals such as zircon and gold. Detrital sulfide survives recycling if deposition and burial in saturated sediments are rapid. QPCs result only if sediment recycling is not accompanied by excessive erosion of fresh basement rock. Uplift of many parts of the Otago Schist belt since late Miocene has raised rocks above the water table, increased erosion rates, and inhibited groundwater alteration and QPC formation. QPC formation is still occurring in Southland, where the water table is high, sediments are saturated and undergoing alteration, and uplift and erosion rates, topography, and fluvial gradients are all low. The QPCs accumulate as residual gravel on the valley floors of low-competence streams that are slowly incising pervasively altered dominantly late Miocene–Pliocene immature conglomerates.QPCs formation essentially represents physical and chemical lagging of precursor strata. Accumulation of detrital gold and other heavy minerals is an inevitable consequence, and most QPCs contain some gold. Three types of significant gold placer have developed in the QPCs. Type 1 placers are essentially eluvial and/or colluvial in origin and form without significant fluvial transport, by residual accumulation in low-competence valleys during low-rate uplift, fluvial incision and QPC formation. Type 2 placers have formed during significant fluvial transport and subsequent fluvial incision, mainly in higher energy proximal and medial reaches of larger pre-marine (Eocene) and post-marine fluvial systems. Type 3 placers formed by wave-base and marine current winnowing in the shallow shelf setting during low-rate regional marine transgression, especially in the Eocene.  相似文献   

Characteristics of diamondiferous Plio-Pleistocene littoral deposits within the palaeo-Orange River mouth, Namibia     

R.I. Spaggiari  B.J. Bluck  J.D. Ward 《Ore Geology Reviews》2006,28(4):475

The Orange River, the principal conduit transporting diamonds from hinterland sources to the Namibian coast in post-Cretaceous times, is characterised by an extreme wave dominated delta that has given rise to a progression of coarse rudaceous littoral deposits preserved onshore for > 150 km north of the mouth. Under the long-lived, prevailing vigorous wave, wind and northward longshore drift regimes, the Orange River outfall has been reworked into, amongst others, a series of economically viable, diamondiferous Plio-Pleistocene onshore gravel beach deposits. These placers comprise spits and barrier beaches in the proximal reach within the palaeo-Orange River mouth that, after ca. 5 km northwards, merge into extensive but narrow linear beaches that, in turn after ca. 70 km, give way to pocket beaches. Gravel and diamond size decreases northwards away from the ancestral Orange River mouth. The linear and pocket beach types have considerably higher diamond content but lower average diamond stone size than the two proximal units that are characterised by low diamond grade but comparatively large average diamond size. Given the risk of delineating low grade alluvial diamond deposits accurately, we present here sedimentological reconstructions of the subtidal, intertidal and supra-tidal facies that constitute the spit and barrier beach sequences, based largely on face mapping of exploration trenches and open-cast, mine cuts, as well as the results of large tonnage, sampling campaigns. Diamond distribution is also linked convincingly to basic littoral processes that were operational within the palaeo-Orange River mouth during the complex transgression that gave rise to the + 30 m package in Plio-Pleistocene times. In both the spit and barrier beach settings, the intertidal deposits prove to be the most promising targets whereas the subtidal sediments are the least economic. The constant raking associated with coarse, cobble–boulder-sized gravel foreshore deposits in an energetic micro-tidal wave regime increased the average diamond stone size in the intertidal deposits to 1 to 2 carats per stone (cts/stn), but the lack of fixed trapsites (no competent footwall within the palaeo-Orange River mouth at that level) prohibited the accumulation of substantially enriched diamondiferous gravels. Consequently, grades of only 1.5 to 6 carats per 100 tons (cpht) are realised. The highest grades (2 to 6 cpht) are found in the landward-facing, intertidal beach deposits on the spits where gentle reworking in that sheltered environment had somewhat enriched and preserved the diamond content. Significantly, the low average stone size of ca. 0.5 cts/stn in this lower energy setting probably reflects that of the general diamond population available at that time. In contrast, the sand-rich subtidal deposits in the spit sequence return the lowest grades (0.1 to 0.5 cpht), similar to those in the slightly younger, subtidal transgressive boulder lags of the barrier beaches. However, the stone size in the spit subtidal sediments is also low (0.1 to 0.5 cts/stn) due to the highly mobile, fine-grained character of those deposits, whereas that in the subtidal transgressive lag is large (2 to 3 cts/stn) as a result of the local, semi-permanent turbulence associated with the boulder-sized clasts in these gravel sheets. Diamond distribution is therefore also influenced by littoral facies and associated beach types, in addition to the spatial and temporal parameters that have already been documented for the onshore marine placers of the southern Namibian coast.  相似文献   

Mineralogy and Geochemistry of Major,Trace and Rare Earth Elements in Sediments of the Hypersaline Urmia Salt Lake,Iran     

Samad ALIPOUR  Khadije MOSAVI ONLAGHI 《《地质学报》英文版》2018,92(4):1384-1395

Urmia Salt Lake(USL) is a hypersaline lake located at the NW corner of the Iran platform. The lake area is estimated to have been over 5000 km~2 at one point, but has now decreased to 1000 km~2 in the last two decades. It contains 4.6×10~9 tons of halite and other detrital and evaporative minerals such as calcite, aragonite, dolomite, quartz, feldspars, augite and sylvite. This study examined the mineralogy and geochemistry of bed sediments along the mid-east toward NE bank sediments collected from 1.5 meters depth and nearby augite placer. Due to the diverse lithology of the surrounding geology, bed sediments vary from felsic in the mid-east to mafic in the northeast. Weathering of tephrite and adakite rocks of the Islamic Island at the immediate boundary has produced a large volume of augite placer over a 40 km length, parallel to the shoreline. Based on the study result, weathering increases from south to north and the geochemistry of the sediments shows enrichment of Mg O, Ca O, Sr and Ba associated with Sr deployment in all samples. Rare earth elements(REE) patterns normalized to the upper continental crust(UCC) indicated LREEs enrichment compared to HREEs with an elevated anomaly of Eu, possibly due to surface absorbance of Mn and Fe minerals, associated with Sr elevation originating from adakites in the lake basin vicinity.  相似文献   

Platinum-group mineral assemblage of the Prizhimny Creek (Koryak Highland)     

A.V. Kutyrev  E.G. Sidorov  A.V. Antonov  V.M. Chubarov 《Russian Geology and Geophysics》2018,59(8):935-944

In the alluvial deposits of the Prizhlimny Creek (southern part of the Koryak Highland), grains of platinum-group minerals are found along with gold. We have established that the grains are native platinum (Pt, Fe) containing Cu (up to 5 wt.%), Os (up to 8 wt.%), and Rh (up to 2 wt.%). Inclusions in the platinum are native osmium (the content of Ir impurity reaches 12 wt.%, the average content being 0.2–4 wt.%), an unnamed intermetallic compound of composition PtRh, sulfides and arsenides of PGE (cooperite, laurite, malanite, cuproiridsite, cuprorhodsite, sperrylite, hollingworthite, unnamed compounds PdS, (Ir,Ru)S₂, (Ir,Pt)S₂, Cu, and Fe (bornite, chalcopyrite), chromite, and Cr-magnetite. Replacement of native-osmium crystals by compound IrO₂ is described. It has been established that this compound formed during oxidation accompanied by the replacement of isoferroplatinum by native platinum. The data obtained agree with the results of study of platinum-group mineral assemblages from placers localized in weakly eroded Ural–Alaskan-type massifs whose apical parts formed under high oxygen activity conditions. Clinopyroxenites of the Prizhimny massif are considered to be the potential source of PGE.  相似文献   

莫桑比克楠普拉地区砂金垂向搬运成因模型研究     

潘刚  曾勇杰  刘峰  康涛  许生武  徐涛  宋英昕 《地质论评》2021,67(Z1):67z1185-67z1186

  相似文献   

鲁中南地区第四系河流砂金成矿特征的研究   总被引：1，自引：0，他引：1  

朱成文 《海洋地质与第四纪地质》1991,11(1):29-40

本文研究了鲁中南地区河流砂金富集成矿特征及成矿时代.区内第四系出露时代齐全,成因类型繁多,岩性复杂.河流砂金矿层主要位于冲积或冲洪(洪冲)积物的底部,即古老变质岩系基岩面之上的含泥砂砾或砾砂等粗粒沉积物中.据资料和第四纪以来气候的冷暖变化,区内河流砂金的成矿时代可划分为中更新世(早期)、晚更新世(早期)和全新世(早、中期).  相似文献