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1.
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
2.
The mineral field structure of a complex placer is a set of features reflecting the distribution and correlation of useful
and accompanying placer-forming minerals, their variation trends, the ordering degree of mineral assemblages, inhomogeneity
levels, etc. The mineral field structure is one of the most important characteristics of polymineral placers. Along with other
properties, it allows one to judge the regional and local formation condition of a placer and to assign it to a certain dynamic
class. The informativeness of this parameter increases if the mineral field inhomogeneity of complex placers is estimated
using various statistical models, in particular, the method of major components, which is one of the modifications of the
factor analysis. This method allows one to restore the structure of such a multifactor system as mineral assemblages of complex
heavy-mineral placers. This analysis yields particularly interesting results in the reconstruction of formation environments
of fossil placers that have lost connection with the recent topography (Devonian gold-diamond-rare metal placers in the middle
Timan region and Mesozoic-Cenozoic titanium-zirconium placers in northern Kazakhstan). It is demonstrated that the mineral
field of a proximal polymineral placer is extremely disordered; its mineral assemblages primarily reflect the provenance rock
composition and only insignificantly the formation environment of the placer itself. The mineral field of a complex coastal-marine
placer of heavy minerals (CMP), in contrast, reflects practically exclusively the lithodynamic situation within the shoreline
zone, including an influence of local factors. Only in exceptional cases, the inhomogeneity of the mineral field of a certain
CMP reflects an additional influence of rocks of the source area. 相似文献
3.
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
4.
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5.
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
6.
Typomorphic features of placer gold in the eastern Siberian Platform were studied to determine its genesis. It was established
that this region contains abundant alluvial bar placers, which were formed mainly by the erosion of gold reservoirs of different
ages. Discovery of gold with the points of eolian reworking in the Quaternary sediments allows us to predict the eolian gold
placers in individual areas of the northeastern and central parts of the eastern Siberian Platform. Identification of two
types of gold on the basis of typomorphic features in the Cenozoic deposits indicates that placer gold was mainly derived
from the Precambrian sources spatially confined to the exposure of ancient basement, as well as from local ore occurrences
related to the Mesozoic tectonomagmatic activation. Thus, two main stages of ore formation (Precambrian and Mesozoic), were
substantiated for the first time in the eastern Siberian Platform. 相似文献
7.
N. G. Patyk-Kara 《Lithology and Mineral Resources》2002,37(5):429-441
Boundary conditions of the placer formation environment are discussed on the basis of a comprehensive study of approximately 40 placer-forming minerals and examination of the following features of minerals: stability under different conditions of migration and redeposition; capacity to be concentrated in a certain grain size class; and industrial requirement of the raw mineral quality. It is suggested that the migration capacity of placer-forming minerals is realized in a wide range of conditions. The work discusses specific features of the transformation of placer mineral assemblages during the scattering and relative concentration in local structural-sedimentation traps (denudation cycle) and the absolute concentration and development of new parageneses in terminal sedimentary basins. The role of structural-sedimentation traps in the formation of large and superlarge placers is demonstrated. It is shown that all types of continental lithogenesis are valid for placer formation, although each type can contribute some specific features to the placer-forming process. Five megaepochs of placer formation are identified in the Earth's history. The duration of Phanerozoic megaepochs, except the last (incomplete) one, is approximately 100 Ma. In terms of placer productivity during the Phanerozoic, the second half of the Paleozoic ranks below the Cenozoic megaepoch. 相似文献
8.
9.
Z. S. Nikiforova B. B. Gerasimov E. G. Glushkova A. G. Kazhenkina 《Geology of Ore Deposits》2013,55(4):265-277
The data on typomorphism of placer gold and its localization in the eastern Siberian Platform have been integrated for the first time. The alluvial, pseudolode, and eolian morphology of gold determines the origin of placers, which is explained not only by hydrodynamic but also by eolian processes. The recent and older alluvial (Au-bearing reservoir rocks in the second case), as well as eolian (unconventional type), genetic types of placers are recognized in the given territory. Precambrian and Mesozoic stages of ore formation are distinguished by the set of typomorphic attributes of placer gold (chemical composition, microinclusions, internal structure, etc.). On the basis of distinguishing features of placer gold, Precambrian lode deposits of great depth spatially related to outcrops of the basement have been forecasted for the first time and classified into low-sulfide gold-quartz, Au-bearing banded iron formation, Au-Cu porphyry, and Au-PGE types. The inferred shallow-seated gold-silver and gold-sulfide-quartz disseminated deposits occur locally and are related to the Mesozoic tectonomagmatic reactivation. The elaborated methods and approaches to the study of placer gold typomorphism in the eastern Siberian Platform also could be helpful in providing insights into placer origin, and forecasting and prospecting gold deposits on the East European Platform, which is close to the Siberian Platform in geological evolution. 相似文献
10.
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
11.
Z. S. Nikiforova S. G. Prudnikov V. I. Lebedev Ch. K. Oidup E. G. Tulaeva 《Lithology and Mineral Resources》2007,42(1):21-27
Issue of the influence of eolian processes on the formation of gold placers in the Tuva region is considered. It has been revealed that the formation of placers is related not only to hydrodynamic processes but also to eolian processes, which are reflected in the formation of relief, redistribution of metal, and reworking of the useful component. Study of typomorphic features of the eolian gold and regularities of its redistribution revealed the possibility of discovery of a new type of placer gold (eolian and heterogeneous placers). 相似文献
12.
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
13.
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
14.
This paper presents materials on one of the units with PGE ore mineralization in the Pana Massif: the results of a detailed petrographic study and microprobe analyses of silicate and sulfide minerals and of the examination of mineral assemblages, typomorphic features of minerals, their crystallization succession and P–T conditions of this crystallization in the mineralized unit and the host mineralized and barren rocks, and the distribution of the fluid phase in them. Metamorphic processes that accompanied the development of the sulfide and PGE mineralization zones are analyzed, and it is established that the metamorphic evolution was associated with changes in the mineralogy of the rock and the composition of fluid in it. This process was of a unidirectional and systematic character and can be realistically reproduced in physicochemical models. The results of our research make it possible to assay the effect of P–T parameters and the fluid regime on the component composition of the solid phases and volatile components during the origin and localization of the PGE ore mineralization. 相似文献
15.
V. I. Gvozdev N. A. Goryachev A. S. Vakh D. G. Fedoseev B. I. Semenyak 《Russian Journal of Pacific Geology》2013,7(6):403-415
A collection of quartz veinlets with ore mineralization sampled from the dumps of the abandoned pit of the Kirov mine was analyzed with defining the mineral assemblages productive for gold mineralization and determining the composition of the main ore minerals and their typomorphic features, which are used for interpreting the genesis of the mineral associations and the deposit as a whole. 相似文献
16.
《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
17.
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
18.
S.A. Grakhanov Yu.A. Malanin V.I. Pavlov V.P. Afanas’ev N.P. Pokhilenko A.V. Gerasimchuk A.N. Lipashova 《Russian Geology and Geophysics》2010,51(1):127-135
Large diamond placers have been discovered in a Rhaetian basal horizon (Upper Triassic) in the north of the Sakha Republic (Yakutia) in the drainage areas of the Eekit, Nikabyt, Kelimyar, and Bur Rivers. In typomorphic features the found diamonds and indicator minerals of kimberlites are completely similar to those from Carnian basal horizons but, in contrast to them, are well sorted, and pyropes show features of mechanical wear. Analysis of the geologic evolution of the study area, morphology of diamonds and indicator minerals, and composition of the latter showed that the Rhaetian productive sediments resulted from the erosion of Carnian placers. 相似文献
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20.
N. G. Patyk-Kara A. V. Lalomov A. A. Bochneva O. P. Fedorov R. M. Chefranov 《Lithology and Mineral Resources》2009,44(6):544-556
In the Transural placer region of the western Khanty-Mansi autonomous district (KHMAD), Oligocene-Miocene rocks with titanium-zirconium
potential are represented by mineralogically mature coastalmarine sediments. Source of placers are represented by both the
Uralian weathering crust and placers of older sedimentary rocks. Sedimentation pattern of this period was governed by tectonic
activation of the Uralian mountain system and sequential regressive dislocation of coastal lines from west to east. Location
of perspective sectors was controlled by peripheral segments of local domes of the third order. Study of the mineral composition
of sediments confirms the presence of two diverse (in mineralogy) Cenozoic terrigenous associations—(i) mature oligomictic
association mainly composed of quartzose silty-sandy sediments with minerals of the titanium-zirconium assemblage (Oligocene-Miocene
Complex) and (ii) polymictic (Neopleistocene) association dominated by unstable minerals and rock fragments. In terms of the
set of lithofacies criteria, Oligocene-Miocene rocks are most perspective for the discovery of coastal-marine titanium-zirconium
placers. 相似文献