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《Bulletin of Mineralogy, Petrology and Geochemistry》
JOPC 2020 Vol.22 Number 5
2020, Vol.22 Num.5
Online: 2020-10-01
SPECIAL ISSUE OF PALAEOGEOGRAPHY AND MINERAL RESOURCES
SPECIAL ISSUE OF PALAEOGEOGRAPHY AND MINERAL RESOURCES
807
2020 Vol. 22 (5): 807-811 [
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445
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812
Du Yuan-Sheng, Yu Wen-Chao
Subaerial leaching process of sedimentary bauxite and the discussion on classifications of bauxite deposits
Bauxite is the ultimate fine-grained products of chemical weathering,and thus it is closely linked with the intense chemical weathering. Based on variations of parent rock and weathering processes,the weathering products can be subdivided into laterite and terra rossa,of which the former is formed by weathering of aluminosilicates and the latter is produced by the weathering of carbonates. During the intense chemical weathering,minerals in original subaerial sediments(parent rocks)would suffer a series of processes(dissolution,hydrolyzation,hydration,carbonation,and oxidation)and be destroyed or transformed,leading to formation of new minerals. In the favorable environment,continuously intense chemical weathering would cause the loss of most mobile elements(
e.g
., K,Na,Ca,Mg,Si)and the enrichment of Al,resulting in the formation of bauxite. Although sedimentary bauxites are closely linked with the weathering curst,they show obvious differences in formation processes. Sedimentary bauxites are composed of intense chemical weathering products that are transported from outside of the basin and re-deposited in the basin,while most weathering crusts are transformed from saprolite and/or deluvium in-situ,and they can only form low-grade bauxites. Sedimentary environments also differ in bauxite ore layers and bauxitic claystone layers. Bauxite ore layers are formed in the subaerial environment and controlled by the leaching process of groundwater in the vadose zone. Based on the analysis of bauxitization,this study proposes to use multiple parameters,such as provenance,sedimentation and mineralization,to build the new classification of Chinese bauxite deposits. In this classification,lateritic and karstic types of bauxite deposits are autochthonous or parautochthonous saprolite and/or deluvium,while sedimentary type is dominated by heterochthonous provenance.
2020 Vol. 22 (5): 812-826 [
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448
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827
Zhang Lian-Chan, Lan Cai-Yun, Wang Chang-Le, Peng Zi-Dong, Tong Xiao-Xue, Li Wen-Jun, Dong Zhi-Guo
Changes of oceanic environment before and after the Paleoproterozoic Great Oxidation Event(GOE): Evidence from petrography and geochemistry of banded iron formation(BIF)from the North China Craton
Banded iron formation(BIF)belongs to sedimentary rocks formed in Precambrian marine,which can directly reflect the redox state of the ancient oceans. Mineral composition and geochemistry of BIF can reveal the relative changes of oxygen contents of ancient atmosphere-ocean. The Neoarchean and Paleoproterozoic BIFs widely distributed in the North China Craton(NCC),are the ideal research objects for understanding the changes of the ancient ocean redox environment before and after the Paleoproterozoic Great Oxidation Event(GOE). Our previous studies indicated that the sedimentary facies of the Neoarchean BIF in the NCC are mainly magnetite-type oxide and silicate,with minor carbonate. The sedimentary facies of the Paleoproterozoic BIF are hematite- and magnetite-type oxide,silicate and carbonate,of which the hematite-oxide facies is unique to the Paleoproterozoic BIF. The above mineralogical features suggest that the redox conditions of the Neoarchean and Paleoproterozoic seawater are different. The rare earth element composition of the Neoarchean BIF in the NCC lacks a strong negative Ce anomaly,reflecting that the oxygen content of contemporary seawater is very low and the marine is anoxic. However,a small amount of BIFs in the NCC also present the negative Ce anomalies and a wide range of Th/U ratios,indicating that the local water of the Neoarchean ocean had relatively high oxygen content and was at a weak oxidation state. Compared with the Neoarchean BIFs,the Paleoproterozoic BIFs present a wide range of Ce anomalies(
i.e.
,no Ce anomalies,positive Ce anomalies and negative Ce anomalies). The hematite-bearing BIF has an obvious negative Ce anomalies,implying that the oxygen content and redox state of Paleoproterozoic seawater changed significantly. Combined with the ratios of Ni/Co,V/(V+Ni)and Th/U of the BIFs in the NCC,the Paleoproterozoic oceans exhibited a suboxidation to oxidation environment. Besides,Neoarchean BIF is strongly enriched in heavy iron isotopes and the non-mass fractionation of S isotope is obvious,whereas the Paleoproterozoic BIF is relatively enriched in light iron isotopes and the non-mass fractionation of S isotope is not obvious. It is summarized that the Neoarchean marine is anoxic,but the oxygen‘oasis' may exist locally,implying that photosynthetic oxygen production already existed in the Late Neoarchean. The ancient ocean presented a layered characteristics during and after the GOE,indicating that the shallow water was generally oxidized and the deep water was reduced.
2020 Vol. 22 (5): 827-840 [
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524
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482
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841
Jin Song, Guo Hua, Yu Wen-Chao, Du Yuan-Sheng, Ma Peng-Fei
Evolution of Yanliao aulacogen in the Paleo-Mesoproterozoic and its control on manganese deposit
It is found that the bottom of Sangshu'an subgroup,which belongs to the Mesoproterozoic Gaoyuzhuang Formation located at the Yanliao aulacogen,is rich in manganese. Although there are still different viewpoints on the origin of manganese and the formation environment of manganese deposits,most scholars believe that the manganese is closely related with the extensive rifting background of the Yanliao aulacogen. In this paper,based on the analysis of exploration data on many manganese ores,the Qinjiayu manganese deposit located at Qianxi belonging to the Yanliao aulacogen,is selected. The manganese ore characteristics,ore types,and element geochemistry are analyzed. The results show that manganese mainly comes from submarine hydrothermal fluids. By analyzing the relationship between the distribution of main manganese deposits and the tectonic faults in the Yanliao aulacogen,it is found that the manganese ore of Gaoyuzhuang formation mainly concentrates at the intersections of the northeast-trending main fault and the northwest-trending transverse fault,and the relatively blocked,deep-water stagnant environment surrounded by faults,where the ore layers are thick and show a relatively high grade. It shows that the structure of the Yanliao aulacogen plays an important role in controlling the formation of Gaoyuzhuang manganese deposits. The syn-depositional faults act as channels for hydrothermal activity,providing a major source of minerals for the manganese-forming basins.
2020 Vol. 22 (5): 841-854 [
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439
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855
Yu Wen-Chao, Du Yuan-Sheng, Zhou Qi, Wang Ping, Qi Liang, Xu Yuan, Jin Song, Pan Wen, Yuan Liang-Jun, Xie Xiao-Feng, Yang Bing-Nan
Coupling between metallogenesis of the Cryogenian Datangpo-type manganese deposit in South China and major geological events
The exploration of the Cryogenian manganese deposits in the Datangpo Formation of South China has achieved great progress in recent years. It is concern in the long term there are many studies on this manganese deposits due to its particularity in the temporal and spatial distribution and the mineralization background. In this paper,we systematically summarize the previous achievements on the Datangpo-type manganese deposits. Besides,we also review current findings of Neoproterozoic global geotectonics,palaeoclimate evolution,ancient marine chemistry,and microbial evolution etc. The possible linkage between the massive metallogenesis of the Cryogenian Datangpo manganese deposits in the South China and Neoproterozoic major geological events is established. The break-up of Rodinia supercontinent led to the widespread rift basin systems in the world since the Middle Neoproterozoic. The Nanhua Basin in South China,which is a manganese-forming sedimentary basin,developed from the rift basin. The rift basin provided space for manganese deposits and controlled the distribution of manganese deposit. The hydrothermal activities at the bottom of the basin provided favorable manganese source. During the Neoproterozoic ice period(“Snowball Earth”event),global ice-sheets cut off or hindered exchanges of mass and energy between different spheres of Earth,which may lead to the widespread anoxic condition in the ice age ocean. The palaeoclimate changes during the glacial-interglacial period led to the disappearance of ice-sheets and the triggering of mass and energy exchanges between different sub-systems of Earth,followed by the variation of redox condition of the ancient sea. For the Nanhua Basin,the oxidation of surface water and the oxygen-bearing base flow provided the oxidation environment for the precipitation of manganese. Besides,new evidence indicated that manganese microbiological mineralization was the potential mechanism for manganese deposit under the microbial resuscitation condition during the interglacial period. All these major geological events have complicated connections and they provided essential metallogenic conditions for the sedimentary mineralization of “Datangpo”manganese deposit. It is believed that there is a coupling between the sedimentary metallogenesis of the Cryogenian Datangpo-type manganese deposit in South China and Neoproterozoic major geological events.
2020 Vol. 22 (5): 855-871 [
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441
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872
Deng Xu-Sheng, Du Yuan-Sheng, Yu Wen-Chao, Wu Kai-Bin, Lu Shu-Fan, Zhang Han-Bin
‘Qianzhong Uplift’ and evolution of the Late Paleozoic palaeogeography and its control on formation of bauxite in Guizhou Province
The Early Paleozoic regional uplift(e.g.,the Qianzhong Uplift)and sea-level changes had obviously controlled the evolution of the Late Paleozoic palaeogeography and paleogeomorphology in Guizhou Province. However,the formation time and evolution of the Qianzhong Uplift is still in debate,which limits the understanding of the Permo-Carboniferous paleogeographic and paleogeomorphologic evolution that formed bauxite in Guizhou. In this paper,based on field surveys and data collection,we established the palaeogeography of several important geological periods from the Late Cambrian to Permian in Guizhou,and re-recognized the formation time and evolution of the Qianzhong Uplift,and revealed the coupling relationship between the Qianzhong Uplift and Guizhou bauxite formation. During the Cambrian to early-middle Early Silurian,the continent-marine transitional facies were missed in the northern margin of the Qianzhong Uplift,central Guizhou Province,such as Bijie,Jinsha and Zunyi. The large-scale uplift of the central Guizhou Province should begin with the tidal flat deposits of the Hanchiatien Formation in the Early Silurian. Because of the Qianzhong Uplift,the central Guizhou and Zunyi areas experienced long-lasting and intense weathering and erosion,forming karst depressions,funnels,and canyons in the Early Carboniferous. The karst landform provided material conditions and location for the formation of bauxite deposits in the Early Carboniferous. The bauxite ore formed under intense chemical wreathing and leaching induced by the glacio-eustasy and paleoclimate fluctuations. The early long-lasting and intense weathering and erosion occurred in the northern Guizhou along with the Permo-Carboniferous glacio-eustasy,had leaded to the formation of coastal wetland and depressions,which were favorable places for the Early Permian bauxite formation. The Early Permian bauxite ores in Guizhou Province have an obvious coupling relationship with the Late Paleozoic Ice Age.
2020 Vol. 22 (5): 872-892 [
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511
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435
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893
Zhang Ya-Guan, Du Yuan-Sheng, Liu Jian-Zhong, Wang Ze-Peng, Deng Chao
Phosphogenesis of phosphorite from the Sinian Doushantuo Formation in Guizhou Province and its coupling relation with the Neoproterozoic Oxygenation Event
Phosphate deposits of the Ediacaran Doushantuo Formation accumulated in the central Guizhou Province are the typical phosphate-rich sediments during the Neoproterozoic Phosphogenic Episodes,which occurred after the “Snowball Earth”period and Neoproterozoic Oxygenation Event. However,the mechanisms of phosphate enrichment in seawater have always been hotly debated,and the research for correlations between phosphogenesis and transition of Ediacaran palaeo-ocean environments is still unsubstantial. This study focused on the sedimentological,petrological,mineralogical and geochemical analyses on the Doushantuo pristine phosphorite in Weng'an,Zunyi and Danzhai area. Documented by spherulitic phosphorites in the Lower Phosphorite beds from Weng'an area that contain abundant autogenetic Fe-bearing minerals such as pyrite and glauconite and show weak Ce negative anomaly,Fe-redox pumping in low-oxygen environments are the important phosphogenesis mechanism but only limited in coastal waters in the Early Doushantuo Period. Phosphorite in the Upper Phosphorite beds deposited within organic-rich beds and contain massive biological fossils suggests that phosphogenesis might have been triggered by degradation of organic matter and biological action in the Late Doushantuo Period,and distribution of phosphatic sediments extended to the deeper shelf to slope setting. Obvious Ce negative anomaly implies the increase of oxygen content in seawater. The transition of phosphogenesis mechanisms and the expansion of phosphorite deposits are the sedimentary response of ocean oxygenation,and the associated evolution of metazoans also changed the redox conditions of the deep seawater. These sedimentary and geochemistry data reflect the closed coupling relation between Doushantuo phosphorite in Guizhou Province and the Neoproterozoic Oxygenation Event.
2020 Vol. 22 (5): 893-912 [
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913
Liu Jian-Zhong, Wang Ze-Peng, Du Yuan-Sheng, Zhang Ya-Guan, Wu Wen-Ming, Chen Guo-Yong, Fu Zhi-Kang, Wan Da-Xue, Wang Da-Fu, Tan Dai-Wei
Enrichment mechanism of phosphorite deposits and significant breakthrough in “Triunity Model”for ore prospecting in the Sinian Doushantuo Formation of eastern Kaiyang region,Guizhou Province
Package exploration area in the eastern Kaiyang region is located at the southeastern margin of the Yangtze block,which is the concentrated distribution area of high-grade phosphorite deposits in China. The comprehensive studies of sedimentology,petrology,stratigraphy and palaeogeography in Doushantuo phosphorite ore-bed of the Kaiyang region show that the phosphorite deposits were controlled by the open shallow coastal sedimentary environment formed by denudation and deplanation of the Central Guizhou Oldland. Phosphorite lithofacies associations,mineralogical features and sedimentary structures indicate that the phosphorites had experienced “three stages of mineralization process”in the Kaiyang region: The first pristine bio-chemical phosphogenesis stage,the second winnowing and reworking stage and the last exposure and leaching stage. The winnowing and reworking processes are the key mechanism to the formation of the thick and high-grade phosphorite. According to the “Triunity Model”metallogenic theory,the research team confirmed the bedded distribution along the open phosphatic shore in the north of the Qianzhong Oldland,constructed the metallogenic model and ore prospecting model,and determined that the shoreface is the major target area of high-grade phosphorite ore. The research team have achieved the innovation of phosphorite metallogenic theory and broke through the bottleneck of phosphorite deposits exploration by cooperating of industry-university-research,and the metallogenic range was expand from 250
k
m
2
to 1000
k
m
2
and quantity of predicted resources increased from 94.42
m
egatons to 1.3 giga-tons. The prospection verification in the part of areas estimated the ore resources of phosphorite deposits(Inferred and predicted resources) of 548.92 megatons,especially the newly added high-grade phosphorites 357 megatons,achieving significant breakthrough of ore prediction of high-grade phosphorites in China.
2020 Vol. 22 (5): 913-928 [
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370
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929
Yang Hai-Ying, Xiao Jia-Fei, Hu Rui-Zhong, Xia Yong, He Hong-Xi
Formation environment and metallogenic mechanism of Weng'an phosphorite in the Early Sinian,Central Guizhou Province
Weng'an phosphorites are located at the east of Central Guizhou oldland and are important constituent of Hubei-Hunan-Guizhou phosphorite belt. Among them,the Datang ore block developed intact Early Ediacaran stratigraphic sequence,and the phosphorite occurred in the Doushantuo Formation which are divided into the lower layer of dolomite, layer A, the upper layer of dolomite, and layer B. Geochemistry showed that the P
2
O
5
concentration of phosphorites in the layer A was higher than that of layer B,while the Sr and Mg/Ca were opposite. These characteristics indicate the degree of aridity and torridity increased from layer A to layer B.
δ
13
C,
δ
18
O,and Z value in layer A are -4.30‰-2.03‰, -11.30‰-7.53‰, and 112119,respectively,and those of layer B are -1.16‰1.49‰, -8.41‰-2.26‰, and 123129,respectively,indicating that the salinity increased from layer A to layer B. Ce
anom
of the layer A are greater than -0.1, whereas those of the layer B are less than -0.1, suggesting the redox conditions changing from anoxic to oxic. The NASC-normalized REE distribution patterns of the layer A show “left-inclining”,indicating the input of hydrothermal fluids. Furthermore,the Si,Al,and Ti content in the phosphorite and the periodical change of
δ
13
C indicate the input of terrigenous weathering and deep seawater. The “left-inclining”REE plots,high psephicity,and intraclast and blocky textures of phosphate from the layer A collectively suggest the phosphorite formed via mechanical power of seawater. The “hat-shaped”REE plots and microbial debris of phosphate from the layer B indicate the phosphorite formed via microbially mediated accretionary growth.
2020 Vol. 22 (5): 929-946 [
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420
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947
Yu Wen-Chao, Du Yuan-Sheng, Xiong Guo-Lin, Zhou Jin-Tao, Pang Da-Wei, Deng Xu-Sheng, Weng Shen-Fu, Li Pei-Gang
Detrital zircon records in bauxite deposits of China: Implication for the provenance model and ore deposits classification of bauxite
Based on 3439 detrital zircon U-Pb datapoints collected from the bauxite deposits of China and 297 detrital zircon U-Pb datapoints from underlying clastic rocks,this study reviews the recent progress in the detrital zircon U-Pb geochronology of bauxite deposits in China. Stability assessment of zircon grains in modern tropical weathering profiles proves the chemical and physical stability during the and intense weathering and bauxitization,which makes zircon become a good provenance indicator. Sedimentary provenance study of bauxite deposits in China indicates that even the bauxite deposit developed on the carbonate rocks,there was still considerable input of the weathering aluminosilicate materials. Previous classifications of bauxite deposit are mainly based on the lithology of basement rock and features of ore body,applications of these classifications will cause ambiguities and uncertainties. For widespread parautochthonous and allochthonous detrital zircon grains within Chinese bauxite deposits,parautochthonous and allochthonous criterion is invalid in classification of Chinese bauxite deposits. Here we suggest that the bauxite study requires a new classification of ore deposit,which should consider the weathering process of bauxite deposits as well as the position of bauxite deposit in the sedimentological framework. Although detrital zircon study provides important constrains for the provenance of bauxite deposits,combination of regional geological background and the geochemical characteristics are still essential for the comprehensive cognition of source materials.
2020 Vol. 22 (5): 947-964 [
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965
Liu Xue-Fei, Wang Qing-Fei, Ma Yao, Li Zhong-Ming, Zhao Li-Hua, Zhou Zhi-Hui, Liu Bai-Shun, Ma Xin-Li
Provenance of iron, bauxite and clay deposits of the Carboniferous Benxi Formation in southern margin of North China Craton: An example from Da'an bauxite and clay deposit of Sanmenxia area,Henan Province
During the Middle Ordovician to Late Carboniferous period,the North China Craton(NCC)was exposed and experienced prolonged weathering that resulted in the formation of large-scale iron,clay and bauxite deposits. The source of ore-forming material has always been a research focus,in particular,whether the sources of the iron ore and the Fe-bearing clay at the bottom of Benxi Formation are the same as the upper bauxite and clay deposit is still unclear. In this study,the Da'an bauxite and clay deposit at the southern margin of the NCC was chosen to carry out a detailed analysis of the micro-region mineral composition and elemental geochemical characteristics for further exploring the sources of iron,bauxite and clay deposits. The composition of the ore-bearing rocks in the Da'an bauxite deposit from the bottom to top includes Fe-bearing clay(locally iron ore),bauxite,and bauxitic clay;locally,in karstic uplift,bauxitic clay layer is directly overlying on the Fe-bearing clay. The Fe-bearing clay is dominated by siderite,pyrite,and illite in the karstic depression,and hematite,illite,and kaolinite in the uplift. Bauxite is mainly composed of diaspore,illite,and anatase,while bauxitic clay is mainly composed of illite. Mineral microanalysis revealed the development of large amounts of moissanite and small amounts of natural silica,silicalite,and chromite at the bottom of bauxitic clay layer. Regional comparison and correlation reveal that the ophiolite in the Shangdan suture zone and Erlangping Group in the North Qinling orogenic belt(NQOB)likely provides source materials for bauxite and clay deposits. The obvious differences in immobile element ratios (e.g., Zr/TiO
2
,Hf/TiO
2
,Nb/TiO
2
,Ta/TiO
2
)between the bottom Fe-bearing clay layer and the upper bauxite and clay layer in Da'an deposit,revealing that they are from different sources. The bottom Fe-bearing clay and iron ore layers are the products of in-situ weathering of underlying carbonates,while the top bauxite and clay are allochthonous. The regional uplift of the NQOB during the Late Carboniferous period provided important ore-forming materials for the formation of the NCC bauxite and clay deposits.
2020 Vol. 22 (5): 965-976 [
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442
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221
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977
Wu Bo, Deng Ke-Yong, Liu Ying-Zhong, Xu An-Quan
Microgeomorphology and its control on the Early Carboniferous Tournaisian bauxite deposits in Longli area of Guizhou Province
In the Longli area of Guizhou,the Early Carboniferous Tournaisian “Fengyuan layer” bauxite was developed. In this paper,based on the geological boreholes,measured profiles and exploration geological point data in study area,the thickness of the aluminous rock series and the ore was calculated. The data of volume thickness,ore grade,and Al/Si ratio were used by Surfer
8
.0 mapping software and the method of microgeomorphology mapping to restore the paleogeomorphology of the Early Carboniferous Tournaisian aluminous rock series. Two paleokarst depressions were found in this area. Fengyuan layer bauxite was produced in paleokarst depressions along the Shuichang-Bimeng-Caoyuan-Gaopo area. Further research on microgeomorphology shows that the high-grade clastic and bean oolitic bauxite is located in the center of paleokarst depressions,while the low-grade dense bauxite is distributed in the center and margin. The paleogeographic research shows that the formation environment of bauxite aluminous rock series in the Fengyuan strata of the Early Carboniferous Tournaisian is a continent-marine transitional facies,including continental facies,paleokarst depression facies and marine facies from north to south. The karst bottomland provides a favorable depositional site for the formation of Fengyuan layer bauxite.
2020 Vol. 22 (5): 977-988 [
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367
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381
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989
Wang Yang, Liu Zhi-Chen, Chen Deng, Xiao Lin, Xiao Liang
Characteristics of metallogenic formation,basin prototype and manganese facies belt of the Permian Maokou Formation in Zunyi area,Guizhou Province
In order to improve the exploration efficiency and reduce the risks and costs of prospecting and exploration,a prediction model for deep prospecting of the Permian manganese deposit in Zunyi area,Guizhou Province was established in this paper. In recent years,four geological maps with the scale of 1︰50000 were established through the project of “Mineral Geological Survey and Prospecting Prediction in Zunyi Manganese Mine Integral Exploration Area,Guizhou”,and the manganese ore formation,basin prototype,and manganese facies belt characteristics of the Permian Maokou Formation in Zunyi,Guizhou have been summarized. In this paper,according to different lithological combinations,structural structures,six types of deposition combinations were found in the manganese mineralization period of the Third Member of Maokou Formation,including manganese-rich formation,manganese-poor formation,manganese-bearing formation,clay rock formation,silicified rock formation and biological limestone formation. Furthermore,the characteristics of central facies,transition facies and marginal facies of the manganese ore are summarized. The prototype of the basin was analyzed from the thickness of stratum,silicified breccia,special sedimentary structure,and AMT geophysical signs. The theories mentioned above were used to guide the manganese prospecting. Three fully hidden prospecting target areas have been delineated,which provide a basis for drilling projects. From 2018-2019,four boreholes were constructed in the Xiejiaba prospecting target area and thick manganese ore bodies were found in all boreholes,and more than 22 million tons manganese ore have been detection. This shows that the theoretical and methods presented in this paper are effective for deep prospecting of manganese ore in Zunyi area.
2020 Vol. 22 (5): 989-1000 [
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349
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256
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1001
Huang Heng, Yan Jia-Xin, Yu Wen-Chao
Evolution of Yizhou aulacogen in Guangxi during Late Paleozoic and distribution of manganese deposits in Early Carboniferous
The palaeogeographic configuration of the shallow water carbonate platform and deep water siliceous basin formed in the Yunnan-Guizhou-Guangxi region during the Late Paleozoic,which developed on the rifting of fold basement and differential subsidence during the Caledonian period. Yizhou-Liuzhou in Guangxi is an important sedimentary boundary in the southern Upper Yangtze carbonate platform. It is also the stratigraphic boundary of Late Paleozoic between middle and northern Guangxi,and it is the tectonic boundary between the southern Xuefengshan and central Guangxi depression during Paleozoic and Mesozoic. In this paper,the evolution of sedimentary basin located at Yishan-Liuzhou region during the Late Paleozoic is reconstructed through the regional stratigraphic correlation and genetic analysis.The elongate Yizhou rifting belt develops from the Nandan-Hechi fault from the west,and extends along Longtou,Beiya,Yizhou,and to Liuzhou. The rifting started at the eastern and western ends of the narrow rifting belt during the Middle Devonian and it developed into the rifting basin during the Early Carboniferous. Due to massive terrestrial siliciclastic filling derived from the Jiangnan Uplift to north,the rifting basin presented the asymmetrical feature and it was eventually filled up at late Early Carboniferous. Many magnesium deposits of Early Carboniferous are found in the rifting basin of Yizhou. The distribution of ore-bearing strata,the depositional succession and sedimentary environment are obviously related with the evolution of rifting basin. They are the evidences of basin evolution,implying the characteristics of rifting aulacogen in central Guangxi,which should be paid more attention in the manganese ore genesis study.
2020 Vol. 22 (5): 1001-1011 [
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351
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234
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1012
Liu Rui, Wang Guo-Qiang, Du Yuan-Sheng, Yu Wen-Chao
Application of nanominerals in research on stacked bauxite deposits
Nanomineral is the mineral that is less than 100
n
m at least one dimension. Aside from the man-made nanominerals,there is a large number of natural nanominerals. With the increasing application of transmission electron microscopy(TEM)in earth science,a large number of natural nanominerals have been discovered in the surface and interior of the Earth. Especially in ore deposit region,nanominerals related to ore bodies are found in various media,and these nanominerals play a unique role in the research of ore deposits. The stacked bauxite deposit is an important source of bauxite because of its large reserve. There are a large number of nanominerals distributed in stacked bauxite deposit,and these ore nanominerals distributed in the deposit in the form of nanocrystals. In addition,the ore minerals in stacked bauxite deposit display changes of the structure and composition in nanoscale. The nanominerals as well as the changes of structure and composition in nanoscale can record the physical and chemical information of bauxite mineralization process,providing a unique window to explore the genesis of the stacked bauxite deposit. This review summarizes the advantages of nanominerals in the research on the stacked bauxite deposit,providing a new method and a new perspective for the understanding of the genesis of bauxite deposit.
2020 Vol. 22 (5): 1012-1020 [
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