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1.
Typomorphic features of native gold and its contents in complex Ti–Zr placers in the southern West Siberian Plain are reported. Three of the placers are of littoral-marine genesis, and two formed under conditions of an alluvial piedmont plain. Native gold from the studied Ti–Zr placers occurs mainly as flattened thin (?0.1 mm) particles which underwent mechanical action. It is marked by wide fineness variation and the abundance of a very fine (990–1000‰) variety. Most likely, this is chemically transformed clastogenic metal. The gold content of the productive bed (5–30 mg/m3 native gold and 8–140 ppb bulk gold) is consistent with the dispersion of heavy ore and accessory minerals during mechanical migration in water flows simultaneously with their concentration on geochemical barriers. The native-gold content of complex Ti–Zr placers shows a higher negative correlation with the primary source–placer distance than those of Ti and Zr minerals and a positive correlation with the degree of hydrodynamic reworking (gravity concentration) of transit terrigenous material. On the southern framing of the West Siberian Plain, some regions of northern Kazakhstan are promising for gold of complex Ti–Zr placers as well as fine- and thin-gold placers, gold-bearing weathering crusts, and primary gold deposits. 相似文献
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3.
I.S. Litvinenko 《Russian Geology and Geophysics》2012,53(7):657-668
We consider the formation of the Dal’nii (Dal’nyaya) eluvial gold placer (Bol’shoi Anyui ore–placer district, western Chukchi Peninsula), related to the Dal’nii (Dal’nee) gold-bearing porphyry Mo–Cu occurrence. The Dal’nii placer is located within the transition between the Kur’ya Ridge and Anyui basin, which has been relatively stable at the recent (Pliocene–Quaternary) tectonic stage. Minor recent uplift has determined the slight denudation of interfluves, the leading role of eluvial processes in the formation of a loose cover on them, and the preservation of the relict matter of pre-Pliocene chemical-weathering crusts (including the oxidized zones of orebodies) in present-day eluvium. The Dal’nii placer consists of relict weathering-crust placers altered by recent eluvial processes in different degrees. Therefore, it is relatively rich in metal, whereas the primary lode contains mainly fine-sized gold, which is almost not released from ore under periglacial lithogenesis in present-day interfluves. We suggest calling this genetic type of placers “residual-eluvial.” The primary lodes being highly eroded (during the formation of residual concentrations, which serve as an intermediate reservoir for these placers), residual-eluvial placers or their parts might not be directly related to specific orebodies at the present-day level of erosional truncation. 相似文献
4.
The structure and formation conditions of secondary geochemical haloes above the buried and flooded placers and their submarine sources in the nearshore shelf zone are considered with a special emphasis on the geochemical processes in placers. It is shown that these processes are most contrasting during periodical emergence and submergence of the shelf. They are of crucial importance in the prospecting for buried mineralization. Submarine tin placers on the Eterikan Strait shelf in the northern framework of Bol'shoi Lyakhovskii Island (New Siberian Islands) were investigated. It was established that ore placers buried below the sealevel are accompanied by contrasting supraore anomalies that penetrate the entire overlying sedimentary sequence and reach the seafloor. The most contrasting anomalies of ore element assemblages are typical of the modern active layer of bottom sediments. It plays the role of an efficient complex geochemical barrier that can accumulate the geochemical information on underlying sediments. Facts demonstrating the efficiency of prospecting works within contours of these anomalies and discovery of buried submarine placers are presented. 相似文献
5.
V. A. Stepanov L. I. Rogulina A. V. Melnikov D. V. Yusupov 《Geology of Ore Deposits》2007,49(7):619-623
The Dambuki ore cluster of the Upper Amur region is characterized by numerous and high-grade gold placers. A few small primary deposits and occurrences of gold-quartz type were formerly considered to be the main source of placers. However, the study of widespread Early Cretaceous Cu- and Ni-bearing ultramafic intrusions has shown that gold occurring in primary Cu-Ni ores and products of their weathering practically does not differ from placer gold in morphology, fineness, or geochemical features. In both cases, elements typical of Cu-Ni ore (Cu, Fe, Pd, Ni, etc.) are detected as impurities of gold particles. These data indicate that the Au-and Pt-bearing Cu-Ni ore mineralization may be the main source of placer gold. This ore mineralization is genetically related to small pyroxenite-cortlandite sills and dikes, abundant in the Dambuki ore cluster. The primary gold-quartz deposits and occurrences also contributed to the placers, but their part was rather small. 相似文献
6.
Lithofacies analyses and paleogeographic reconstructions of the middle Sarmatian sequence in the central Ciscaucasus, which hosts the most promising titanium–zirconium placers of the Stavropol region, indicate that ore components (rutile, ilmenite, leucoxene, and zircon) were mainly delivered to the Stavropol placer basin by the paleo-Volga River from a northern land. Bryozoan organogenic edifices played a significant role in the formation of placers. The organogenic edifices appeared under anomalous (for bioherm formation) conditions of terrigenous sedimentation on the western and northwestern slopes of the Stavropol Uplift, hampered the transport of ore material to the deep-water zone of the basin, and promoted its differentiation in the paleouplift. 相似文献
7.
Zaykov V. V. Kotliarov V. A. Zaykova E. V. Blinov I. A. 《Doklady Earth Sciences》2017,476(2):1212-1216
Microinclusions of ore minerals were found and studied in grains of native gold for characterization of the mineralogy of placer gold of the South Urals. One hundred ten unrounded and poorly rounded grains with a size of 1–2 mm from eight placer zones were studied. Microinclusions of ore minerals were detected in six placers of the Miass zone. The list of minerals includes sulfides, arsenides, Cu-bearing Au, and PGEs. All microinclusions show links to certain deposits of ore gold and chromite occurrences. It is suggested that the northern flanges of the Talovsky and Nurali massifs containing gold placers with PGEs require a search for PGE mineralization.
相似文献8.
Platinum-group minerals (PGM) in primary ores and placers are compared in order to substantiate prospecting guides for layered
and differentiated intrusions containing sulfide Cu-Ni ores with platinum-group elements (PGE). It is shown that supergene
placer mineral assemblages bear information on primary sources and their probable economic value. The mineralogical and geochemical
data on the large Siberian intrusions that host Cu-Ni and low-sulfide PGM deposits (Noril’sk 1, Kingash, Chinei, and Yoko-Dovyren)
are used to elaborate mineralogical prospecting guides based on the comparative study of PGM assemblages in primary ore, heavy
concentrate halos, and hillside sediments. The mechanism of PGM redistribution under supergene conditions is exemplified in
the Chinei deposit. The placer mineral assemblage with prevalence of Pt-Fe alloys, atokite-rustenburgite, sperrylite, and
multicomponent Pd-Sn-Cu-Pb compounds can be used as a prospecting guide for Noril’sk-type primary PGM ore and related economic
placers. The paolovite-sperrylite or sperrylite PGM assemblage in heavy concentrate halos indicates occurrence of Cu-Ni ore
in the prospecting area. Sperrylite with isomorphic admixture of Ir and Os typical of the Kingash pluton could be a orospecting
guide for Ni-bearing mafic-ultramafic intrusions. 相似文献
9.
Patyk-Kara N. G. Gorelikova N. V. Bardeeva E. G. 《Lithology and Mineral Resources》2004,39(6):509-523
Based on the study of the Tsentral'noe deposit, specific features of the formation of mineral assemblages of complex titanium–zirconium placers are considered. The placers formed during the multiple redeposition of clastogenic minerals from source rocks and younger sedimentary rocks (intermediate collectors of titanium–zirconium minerals). The location of erosion and sedimentation zones significantly varied in the Phanerozoic in the adjacent region, resulting in the development of intricate relationships between different-aged terrigenous rocks (possible intermediate collectors) that provided the formation of new mineral assemblages of clastogenic ore minerals. In addition, erosional processes during the continental evolution of the study region could promote the exposure of more ancient rock complexes, the local washout of crystalline basement rocks, and the delivery of ore minerals from the latter rocks to the coastal zone of sedimentary basins. The aim of this communication is to attract the attention of researchers to the issue of the formation of mineral assemblages of complex placers of heavy minerals with similar hydraulic grain dimension and migration capacity for concentration in a rather narrow grain size range. Such mineral assemblages only slightly inherit the primary compositional features of provenances and primarily reflect changes in the sedimentation environment. 相似文献
10.
自然重砂是地质体经自然风化、剥蚀、搬运、沉积等地质作用而分离出的单矿物(或矿物组合)。自然重砂矿物晶体由于仍然保留有许多矿物成因信息,包括颜色、形态、化学成分、物理性质和矿物组合等特征,因此常用于追溯源区地质体或者找矿勘查。这种方法被认为是一种经济实用的找矿方法——自然重砂测量。本文基于全国自然重砂找矿的数据资料,系统梳理了自然重砂的矿物类型、出现频率及其分布等特点,分析了自然重砂的矿物组合和成因矿物学特征,研究了自然重砂矿物的源区烙印、搬运距离及标型指示矿物组合特征,探讨了自然重砂成因矿物学研究意义及其找矿应用前景。自然重砂矿物的颜色、形态及内部结构依然保留着明确的成因矿物学信息:其颜色和晶体形态具有继承性而与其源区母体联系起来,体现源区母体的特性;其矿物组成可分出残余原生重矿物(包括造岩矿物、副矿物、矿石矿物等)和新生重砂矿物两个部分,如赤铜矿、孔雀石等反映着源区岩性体的成分或者赋存状态特征,其矿物组合也在很大程度上继承原生共生矿物而体现诸如有无矿化等意义;重砂颗粒的磨圆度、边界光滑性等表面特征反映搬运距离,有利于明确响应源区母体或者物源,而具有良好的找矿指示意义。 相似文献
11.
I. S. Litvinenko 《Russian Journal of Pacific Geology》2008,2(2):175-186
The main features of the migration and accumulation of fine and ultrafine gold during the evolution of placer-forming processes in northeastern Russia are discussed. The results of loose sediment sampling (over 2000 samples) with a screw separator and strake facilities have been taken into consideration. The approximate grades and potential resources of gold were estimated for various genetic types of placers. The most favorable conditions for the mobilization and accumulation of fine and ultrafine gold in the placers of northeastern Russia prevailed during the Paleogene to Miocene stage of the evolution of orogenic morphostructures, when the residual (illuvial and alluvial) placers were formed. During the Pliocene to Quaternary stage, the tectonic activation caused the reworking of placers by slope and fluvial processes and resulted in the formation of new hillside and alluvial placers. At this stage, the dispersal of fine gold fractions prevailed over accumulation. Under conditions of the periglacial lithogenesis of the Pliocene to Quaternary tectonic activation, the formation of new placers with fine and ultrafine gold derived from primary sources was suppressed due to the low rate of metal release in the process of physical weathering. In terms of the economic importance of placers with fine and ultrafine gold, residual, eluvial, or hillside placers, as well as alluvial stratal placers located in low-order (and partly medium-order) stream valleys, are the most attractive in northeastern Russia. The primary sources of such placers comprise gold-bearing porphry copper, gold-sulfide-quartz, and other hydrothermal deposits with similar placer-forming capability, as well as gold-quartz stockworks. The grade of fine and ultrafine gold in such placers may be as high as a few g/m3. The placers located in the constratal alluvium of graben-type valleys and the bar and floodplain placers in the areas with stockwork-like orebodies containing fine (<0.25 mm) gold are regarded as prospective objects. 相似文献
12.
Physical and thermal treatment of phosphate ores — An overview 总被引：1，自引：0，他引：1
The annual consumption of phosphate rock approached 150 million tons. The marketable phosphate is usually 30% P2O5 or higher. The run-of-mine material is mostly of lower grade which needs processing or upgrading. The processing techniques of phosphate ores depend mostly on the type of associated gangue minerals present in the mined rock. In some cases, simple, inexpensive techniques are enough to produce the required grade. For example, crushing and screening is used to get rid of the coarse hard siliceous material, and attrition scrubbing and desliming is used to remove the clayey fine fraction. If silica is the main gangue material, single-stage or double-stage flotation is the conventional mineral processing technique used in this case. If the ore is igneous carbonatitic alkaline or ultra basic phosphate deposit, crushing, grinding, scrubbing, and flotation associated with other steps such as magnetic and/or gravity separation is proved to be successful in upgrading this type of ore. The sedimentary phosphate ores having carbonate-apatite as the main phosphate minerals and containing carbonates (calcite and/or dolomite) represent a challenge in the field of phosphate concentration due to similarity in the physico-chemical properties of surfaces of the ore constituents. Also, if considerable amount of organic matter constitutes the main gangue material, upgrading of the ore becomes difficult. New flotation systems (techniques and reagents) are being developed to treat these challenging phosphate ores. Furthermore, calcination is another solution for upgrading these difficult-to-treat types of ores. However, calcination is indicted with some controversial drawbacks. This overview discusses and summarizes the State-of-the-Art and the existing efforts to overcome these problems and to produce a high-grade phosphate product suitable for fertilizers and other phosphate compounds. 相似文献
13.
菲律宾迪纳加特岛汇洋镍铬矿区发育板块碰撞成因的蛇绿岩,主要岩性为纯橄岩和方辉橄榄岩,与铬铁矿化关系密切,在纯橄岩和方辉橄榄岩的过渡带中铬铁矿化较为集中,铬铁矿多呈薄层块状或浸染状与围岩岩性条带呈"互层状"产出,块状、浸染状的铬铁矿重复出现;矿区内原生铬铁矿化非常普遍,虽然未构成原生铬铁矿体,但为次生红土型铬铁矿的成矿提供了丰富的物质来源。矿区内第四系中赋存有残坡积红土型铬铁砂矿,并与同类型镍矿共生;铁质红土层是最佳的含矿层位,松散状红土层次之;铬铁矿体呈层状、似层状,有3个铬铁砂矿化区,矿体厚度5~7m,铬铁矿品位w(Cr2O3)=2.0%~4.1%。 相似文献
14.
A. A. Konstantinovskii 《Lithology and Mineral Resources》2005,40(1):9-20
In the eastern Baltic Shield, coastal-marine and continental sediments of the Vendian platform cover have been drilled and recovered on either side of the regional Vetrenyi Poyas Uplift. Summarization of the geological prospecting material and new data make it possible to predict the existence of complex (gold and platinum group metal) placers in basal layers of these deposits.Translated from Litologiya i Poleznye Iskopaemye, No. 1, 2005, pp. 12–24.Original Russian Text Copyright 2005 by Konstantinovskii. 相似文献
15.
Semi-arid climatic conditions were responsible for the evolution of the vast savanna that stretches across central Africa and for the evolution of placers in this area that carry gemstones, rare earth element minerals and zircon- and titanium-bearing minerals. In combination with a polystage peneplanation, chemical weathering contributed to the emplacement of four different types of placer deposits during the Cenozoic in Malawi. Eight landform types have been defined by their geomorphological form, geometry, grain size parameters, stratification, fabric and rock contacts. Each type describes the landscape of the savanna and can be related to the emplacement of placer types within this morphoclimatic zone. Residual to eluvial placers, represented geomorphologically by landform type V, came into existence under strong chemical weathering during a period of alternating peneplanation and valley incision into soil and saprolite. Gentle valley-side slopes or elongated interfluves have a low gradient favorable for the formation and preservation of eluvial to colluvial placers (landform type Ic). Fluvial placers become economic only on outwash plains of tributaries near the confluence with their trunk rivers, beyond the point of inflection (landform types III, II). In the lower reaches of fluvial drainage systems around shallow lakes, fluvio-deltaic placers evolved during periods of rapid uplift and regression of the lake (landform type IV). Other landform types established throughout this study are cast in the role of ‘ore guides’ or, alternatively, have a negative impact on the likelihood of placer formation. The key associations of landforms discussed in this paper may be used as a geomorphological-sedimentological tool in search of modern continental placer deposits in areas where semi-arid climatic conditions occur(red) during the Cenozoic. 相似文献
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《Russian Geology and Geophysics》2007,48(10):783-798
This paper deals with the behavior of fine gold particles (0.25–0.1 mm) and gold dust (<0.1 mm) during the formation of alluvial placers in denudation areas in southern West Siberia. Native gold particles with a low settling velocity, <5–10 cm/s, such as dust (<0.1 mm) and fine flat particles, are transported with a river stream beyond denudation areas. This easily migrating gold participates in the formation of lithochemical flows, which are an important indicator of gold mineralization. It occurs in the upper beds of alluvial section. Heavier fine gold particles are partly retained at the site of river activity, and the rest are partly redeposited in cooler parts of placers, being graded according to their settling velocity, as evidenced from the direct relationship between the flatness and size of gold particles. Fine gold particles do not form large accumulations in alluvial autochthonous placers. The main typomorphic features of fine gold particles and gold dust are their abundance in ore sources, compositional similarity to larger gold fractions, and high migration ability. In contrast to morphological features of gold, these ones remain stable during the river drift. 相似文献
18.
A mathematical model of coastal–marine tin placers formed in the alongshore drift flow is developed using the mass balance method. The physical meaning of the coefficients included in the model is considered. Coastal–marine placers are quantitatively estimated. The simulation adequacy is confirmed by the data on coastal–marine tin-bearing placer deposits at the Pevek ore cluster (Chaun Bay, East Siberian Sea). We suggest that the obtained equations be used for surveying and exploration. Identified patterns are used to estimate the tin placer potential in one of the coastal areas in the Eastern Arctic Basin. 相似文献
19.
A. A. Kremenetsky N. A. Gromalova E. Belousova L. I. Veremeeva 《Geology of Ore Deposits》2011,53(6):455-473
Zircons were studied from the Ti-Zr placers of the Murray Basin (Mindarie and WIM-150 deposits) and metamorphic rocks of the
adjacent Kanmantoo Belt and the Ballarat Trough in Southeast Australia, and from Russian basins with Ti-Zr placers: the Cenomanian-Turonian
and Poltavian basins in the East European Platform and the Sarmatian basin in the northern Caucasus, Stavropolye, and Kalmykia.
The study of the primary source → weathering mantle → intermediate reservoir rock → economic placer system includes (1) morphostructural
and paleofacies reconstructions of the studied territories; (2) quantitative analysis of ore mineral distribution in each
element of this system; and (3) study of zircon typomorphism from the feeding source to the basin, where Ti-Zr placers have
been deposited. In all elements of the system studied, zircons were examined using optical and cathodoluminescence microscopy,
an electron microprobe, mass spectrometry (laser ablation and SHRIMP II), including U-Pb dating, Lu and Hf isotopes, distribution
of trace elements (REE, Y, P), and comparative analysis of indicative ratios: Th/U, HfO2/ZrO2, Y2O3/(Y2O3 + REE2O3), (La + Sm)/(Gd + Yb), etc. Newly formed rims replacing detrital zircon grains and marking the time of late geological events
were identified. The rims differ from the cores in distribution of trace elements. Genetic typification of diverse newly formed
rims is based on discrimination of them by internal structure, isotopic and geochemical characteristics, which are used as
a criterion of relationships between Ti-Zr placers and their inferred feeding sources. Based on these data, a prospecting
model of the buried Ti-Zr placers with estimation of their resource potential has been produced. 相似文献
20.
Z. S. Nikiforova 《Lithology and Mineral Resources》2003,38(6):547-551
The distribution of eolian gold in various Proterozoic–Cenozoic sediments on the East European Platform is considered. Eolian placers of the Timan Ridge are characterized by specific features: significant areal distribution and consistent strike of the thin (0–30 cm) productive bed. Prospecting criteria of eolian gold placer in the study territory can be the presence of gold flakes and other minerals with signs of eolian reworking, specific structure of productive bed, deflation structure of relief, and characteristic lithological composition of sediments. It is concluded that since gold flakes with eolian reworking make up high metal concentrations, such as placer deposits in the Timan Ridge, eolian placers of different age may be found on the East European Platform. 相似文献