Isotope Geochemical Characteristics and Material Sources of Tin--Bearing Porphyries in South China

Tin-bearing porphyries in South China can be divided into the F-rich and F-poorsubtypes. They are high-silica (SiO_2>71%), peraluminous (A/NKC>1.0) and rich inincompatible elements (Rb, Zr, U, W, Sn) and have weak Ce (δCe=0.68-0.82) and strong Eu(δEu=0.01-0.38) negative anomalies. Meantime, they also have low δ_(Nd)(-6.3- -8.4), high^(207)Pb/^(204)Pb (15.588-15.790), medium to high (^(87)Sr/^(86)Sr)_i (0.7084-0.7287) and relatively highδ^(18)O(9.1-10.3‰). These characteristics clearly suggest that the two subtypes of tin-bearingporphyries were derived from the crustal materials. Their differences lie only in the existence ofcertain different components in their source materials. Therefore, there is only one type oftin-bearing prophyry in South China. that is continental crust transformation type.

New Sr Isotope Evidence to Support the Material Source of the Mengyejing Potash Deposit in the Simao Basin from Ancient Marine Halite or Residual Sea

Objective The Mengyejing potash deposit in the Simao Basin is the only producing area of solid potash at present in China. There is still controversy about the material source and distribution of the potash in this deposit （Shen Lijian et al., 2017）, which has influenced not only the prospecting direction and efficiency but also the understanding of the control of Tethys tectonic evolution on the formation and distribution of the mineral resources. This work analyzed the Sr isotope geochemical characteristics of evaporites from core samples in the well MZK-3 in order to further clarify the material source and to explore the potash distribution in the Simao Basin.

Geochemical Tracing of Ore-forming Material Sources of Carlin-type Gold Deposits in the Yunnan-Guizhou-Guangxi Triangle Area --A Case Study of the Application of the Combined Silicon Isotopes Geochemistry and Siliceous Cathodoluminescence Analysis

Abstract This paper deals with characteristics of silicon isotope compositions and siliceous cathodoluminescence of host rocks, ores and hydrothermal silicified quartz of the Carlin-type ore deposits in the Yunnan-Guizhou-Guangxi triangle area. The study shows that primary silicified quartz is nonluminescent but quartz in host rocks and secondary silicified quartz are luminescent by the action of cathode rays. Correspondingly, silicon isotope compositions of host rocks, ores and hydro6thermal quartz veins are clearly distinguished. In strata from the Middle Triassic to the “Dachang” host bed, δ30Si of the host rocks ranges from 0.0% ?0.3%, while that of primary ore-forming silicified fluids from ?0.1% to ?0.4%; in the Upper Permian and Lower Carboniferous strata and Indosinian diabase host beds, δ30Si of the host rocks is from ?0.1% to ?0.2% and that of the primary silicified quartz veins from 0.3 % ?0.5 %. This pattern demonstrates the following geochemical mineralization process, primary ore-forming siliceous fluids migrated upwards quickly along the main passages of deep-seated faults from mantle to crust and entered secondary faults where gold deposits were eventually formed as a result of permeation and replacement of the siliceous ore-forming fluids into different ore-bearing strata. This gives important evidence for the fact that ore-forming fluids of this type of gold deposits were mainly derived from upper mantle differentiation and shows good prospects for deep gold deposits and geochemical background for large and superlarge gold deposits.

Ore-Forming Material Sources of the Shizishan Pb-Zn Deposit in Western Hunan Province,China

Objective The Shizishan Pb-Zn deposit is located in the southeastern margin of the Yangtze Block,and its Pb-Zn orebodies are mainly hosted in the Lower Cambrian Qingxudong Formation limestone.Previous researches have investigated the geological characteristics,geochemistry and fluid inclusions of this deposit.

Rare Earth Elements Geochemistry of Laowan Gold Deposit in Henan Province: Trace to Source of Ore-Forming Materials

The compositions of REE in quartz and pyrite from the main stage of the Laowan gold deposit in Henan Province and that in quartz from Laowan granite were determined by inductively coupled plasma-mass-spectrometry （ICP-MS） to trace the source of ore-forming materials. Meanwhile, the REE compositions of the deposit ore, granite and metamorphic wall rock were also considered for comparative studies in detail. The range of ∑REE of quartz and pyrite from the deposit ores is 4.18 × 10^-6- 30.91 × 10^-6, the average of ∑REE is 13.39 × 10^-6, and the average of ∑REE of quartz in the Laowan granite is 6.68 × 10^-6. There is no distinct difference of REE parameters between the deposit ore quartz and granite quartz. The quartz in gold deposit has the same REE particular parameters as quartzes from Laowan granite, such as δEu, δCe, （La/Yb）N and （La/Sm）N, partition degree of LREE to HREE, especially, the chondrite-normalized REE patterns, but no similarity to those from metamorphic wall rock, which shows that ore-forming hydrothermal fluid is mainly the fluid coming from the Laowan granite magma, rather than metamorphic fluid. Meanwhile, comparison studies on REE features between minerals from the deposit ores and related geological bodies in the deposit show that REE characteristics of minerals can serve as an indicator of ore-forming fluid properties and sources, while the REE characteristics of the bulk samples （such as deposit ores, granites and wall rocks） can not trace the source of the ore-forming materials exactly.

Classification and Source Materials of Continental Crust Transformation Series Granitoids in South China

The granitoids of the continental crust transformation series in South China may be divided into threetypes: (1) synorogenic migmatic and magmatic type. (2) anorogenic continental crust anatexis type, and (3)syncollision type. Based on the results of Sr and Nd isotopic determinations, the source material compositionof the three types of granitoids is calculated with crust-mantle binary mixing simulation. The calculations indi-cate that the granitoids of the first type consist of 78.6-89.7% upper crust endmember materials and15.0-10.3% depleted mantle endmember materials, the granitoids of the second type are composed of 63.7%upper crust endmember materials and 36.3% depleted mantle endmember materials, and those of the third type100% upper crust endmember materials. Hence. the source material composition of the granitoids of all thethree types is dominated by upper crust endmembers.

Ore-forming fluid characteristics and ore-forming materials source of the Tudimiaogou – Yindongshan lead-zinc polymetallic orefield, west Henan

1 Introduction The Tudimiaogou-Yindongshan lead-zinc polymetallic orefield is located in the Tudimiaogou-Weimoshi lead and zinc silver polymetallic metallogenic belt.The belt is an important part of southwestern Henan lead and zinc

Rare Earth Element Geochemistry Characteristics of Laowan Gold Deposit in Henan Province: Trace to Source of Ore-Forming Materials

The compositions of REE in quartz and pyrite from main mineralized stage of the Laowan gold deposit in Henan province and that of quartz from Laowan granite were determined by Inductively Coupled Plasma-Mass-Spectrometry （ICP-MS）. The REE of deposit ore of the Laowan gold deposit, wall-rock and Laowan granite also were studied to trace the source of metallogenic materials in Laowan gold deposit in detail. The range of ∑ REE in quartz and pyrite from gold deposit is 4.18 × 10^-6 - 30.91 × 10^-6, average of 13.39 × 10^-6, 6.68 × 10^-6 of the Laowan granite quartz, obviously lower to REE concentration of deposit, granite and wall-rock. The value of （La/ Yb）N and （La/Sm）N of ore minerals from the gold deposit is 13.23 and 4.17 respectively. The differences in REE parameters, such as δEu, δCe and diffusion degree in REE from light to heavy, among deposit ore minerals and granite mineral are weak. Especially, there are no differences between the chondrite-normalised REE curves of minerals from gold deposit and those of quartzs in Laowan granite, no similarity to wall-rock＇, which shows that ore-forming hydrothermal fluid mainly came from magma fluid resulting from the Laowan granite magma, metamorphic fluid in few. The results also show that REE characteristics of ore minerals in deposit are effective for disclosing oreforming fluid quality comparing with deposit ore＇REE compositions.

Isotopic tracing of ore-forming source materials for Dexing porphyry copper deposit of Jiangxi, China

Dexing copper deposit is the biggest porphyry copper deposit in China. By researching isotopes of C,Si and Cu from the samples of Tongchang and Fujiawu ore-field, the authors found that δ13CPDB values of siderite were close to the δ13CPDB value of original magma; δ30Si values of the samples at the ore-forming stage were close to the δ30Si value range of magma, δ30Si values of partial samples were far away from it; Cu isotopic compositions of massive chalcopyrite formed at the early ore-forming stage are higher than that of veinal chalcopyrite formed at the later ore-forming stage. The results show that ore-forming materials were mainly derived from the porphyry body, and part of them were from wall rock materials.

Further study on the genesis of lamellar calcite veins in lacustrine black shale--A case study of Paleogene in Dongying Depression, China

Lamellar calcite veins are prevalent in carbonate-rich,lacustrine dark shale.The formation mechanisms of these veins have been extensively debated,focusing on factors such as timing,depth,material source,and driving forces.This paper examines dark lacustrine shale lamellar calcite veins in the Paleogene strata of Dongying Depression,using various analytical techniques:petrography,isotope geochemistry,cathodoluminescence,inclusion thermometry,and electron probe micro-analysis.Two distinct types of calcite veins have been identified:granular calcite veins and sparry calcite veins.These two types differ significantly in color,grain structure,morphology,and inclusions.Through further investigation,it was observed that vein generation occurred from the shallow burial period to the maturation of organic matter,with a transition from granular calcite veins to sparry calcite veins.The granular calcite veins exhibit characteristics associated with the shallow burial period,including plastically deformed laminae and veins,the development of strawberry pyrite,the absence of oil and gas,weak fractionation in oxygen isotopes,and their contact relationship with sparry calcite veins.These granular calcite veins were likely influenced by the reduction of sulfate bacteria.On the other hand,sparry calcite veins with fibrous grains are antitaxial and closely linked to the evolution and maturation of organic matter.They contain oil and gas inclusions and show a distribution range of homogenization temperature between 90℃ and 120℃ and strong fractionation in oxygen isotopes,indicating formation during the hydrocarbon expulsion period.The carbon isotope analysis of the surrounding rocks and veins suggests that the material for vein formation originates from the shale itself,specifically authigenic micritic calcite modified by the action of methanogens.The opening of horizontal fractures and vein formation is likely driven by fluid overpressure resulting from undercompaction and hydrocarbon expulsion.Veins may form rapidly or through multi-stage composite processes.Early veins are predominantly formed in situ,while late veins are a result of continuous fluid migration and convergence.Furthermore,the veins continue to undergo modification even after formation.This study emphasizes that the formation of lamellar calcite veins in shale is a complex diagenetic process influenced by multiple factors:biology,organic matter,and inorganic processes,all operating at various stages throughout the shale's diagenetic history.

Sources and control factors of rare earth elements in Late Permian mudstones,Southwest China

The material sources and control factors of rare earth elemems （REEs） for 25 borehole bulk samples from the Late Permian Longtan Formation in Mount Huaying （borehole number： ZK10-6）, Sichuan Province, South China, were investigated. All samples were determined by inductively coupled plasma mass spectrometry （ICP-MS）. The chondrite-normalized distribution patterns of mudstone samples are uniform. All samples belong to the light rare earth element （LREE）-rich type and are enriched in LREEs relative to heavy rare earth elements （HREEs）. The distribution curves of REEs in mudstone are highly similar to Mount Emei basalt and the three periods of REEs enrichment correspond to three Mount Emei basalt eruption cycles in Longtan period. The results indicate that REE patterns are not controlled by materials from the seawater or land plants. The predominant sources of REEs are from terrigenous material as indicated by negative Eu anomaly. So, the sources of REEs are controlled by terrigenous material, and the Mount Emei basalt is the predominant source of terrigenous material. Thus, transgression-regression is another control factor of REEs enrichment.

The Lithospheric Structure in the South China Block from Receiver Function: Implications for the Source of Mineral System

The South China block(SC),composed of Cathaysia(CA),Jiangnan Orogenic belt(JNB),and Yangtze block(YB),is one of the most important poly-metallic metallogenic provinces in the world(Zhang et al.,2013),containing of four famous major Mesozoic metallogenic belts,involving the Middle-Lower Yangtze Fe-Cu-Au metallogenic belt(MYMB).

Study on REEs as tracers for late permian coal measures in Bijie City,Guizhou Province,China

Analyses of Rare Earth Elements （REEs） in 13 coal samples collected from Late Permian coal measures of Bijie City in western Guizhou Province were conducted using Inductively Coupled Plasma-Mass-Spectrometry （ICP-MS）. The results indicated that REEs patterns were not controlled by materials from the sea, whereas the contribution of land plants was about 1%. The major sources of REEs were from terrigenous material as indicated by negative Eu anomaly. There were similar distribution curves of REEs between Bijie＇s coal and Emeishan basalt. M12 coal seam, which had the highest ∑REE, appeared near the boundary between Longtan Formation and Changxing Formation, which was closely correlated to the eruption of Emeishan basalt. The Emeishan basalt contributed to REEs enrichment of M12. So the sources of REEs were controlled by terrigenous material, and the Emeishan basalt was the predominant source of terrigenous material, which dominated the enrichment and pattern of REEs in Late Permian coal measure from Bijie.

Spatial distributions of organic carbon and nitrogen and their isotopic compositions in sediments of the Changjiang Estuary and its adjacent sea area

The spatial distribution patterns of total organic carbon and total nitrogen show significant correlations with currents of the East China Sea Shelf. Corresponding to distributions of these currents, the study area could be divided into four different parts. Total organic carbon, total nitrogen, and organic carbon and nitrogen stable isotopes in sediments show linear correlations with mean grain size, respectively, thus ＂grain size effect＂ is an important factor that influences their distributions. C/N ratios can reflect source information of organic matter to a certain degree. In contrast, nitrogen stable isotope shows different spatial distribution patterns with C/N and organic carbon stable isotope, according to their relationships and regional distributions. The highest contribution （up to 50%） of terrestrial organic carbon appears near the Changjiang Estuary with isolines projecting towards northeast, indicating the influence of the Changjiang dilution water. Terrestrial particulate organic matter suffers from effects of diagenesis, benthos and incessant inputting of dead organic matter of plankton, after depositing in seabed. Therefore, the contribution of terrestrial organic carbon to particulate organic matter is obviously greater than that to organic matter in sediments in the same place.

Geology and Lead-Sulphur Isotope Compositions of the Tongyu Volcanic-Hosted Massive Sulphide Copper Deposit in the Western Part of the North Qinling Orogen, China

The Tongyu copper deposit, located in the western part of the North Qinling Orogen, China, is one of several volcanic-hosted massive sulphide（VHMS） deposits with industrial value and is also a typical example of mineralization related to the subduction and metallogenesis during the Caledonian orogeny. We conducted systematic lead-sulphur isotope geochemical analyses of the Tongyu deposit to understand the possible ore-forming material sources and tectonic settings. Twenty-six sulphide samples yielded clustered δ^34SCDT values of 1.13‰-3.36‰, average 2.22‰, and show a tower-type distribution,implying that the sulphur of the Tongyu copper deposit mainly originated from a mantle source. The Pb isotope compositions of sulphides（^206Pb/^204Pb = 17.59225-18.56354, average 18.32020; ^207Pb/^204Pb =15.51770-15.69381, average 15.66217; ^208Pb/^204Pb= 37.99969-39.06953, average 38.52722） are close to the values of the volcanic host rocks（^206Pb/^204PbPb= 18.10678-18.26293, average 18.21158; ^207Pb/^204PbPb =15.63196-15.68188, average 15.65345; ^208Pb/^204PbPb= 38.43676-38.56360, average 38.49171）, thus consistent with the Pb in ores and volcanic host rocks having been derived from a common source that was island-arc Pb related to oceanic crust subduction. The northward subduction of the Palaeo-Qinling oceanic crust triggered dehydration of the slab, which generated a large amount of high-oxygen-fugacity aqueous hydrothermal fluid. The fluid rose into the mantle wedge, activated and extracted metallogenic material and promoted partial melting of the mantle wedge. The magma and ore-forming fluid welled up and precipitated, finally forming the Tongyu VHMS copper deposit.

Progress of loess research in China

Progress in Chinese loess research made in recent 15 years was introduced in this paper, including mainly distribution and paleoenvironment significance of Chinese loess, new development of loess formation age, red-brown paleosol types and environmental change, loess-paleosol sequence and climate cycles, monsoon strength change during last interglacial and last glacial periods in the Loess Plateau, climate events, and source areas of loess and material.

The geological significance of fossils in the coastal loess in the Bohai Straits and Liaodong Peninsula

Based on the analysis of the characteristics of the fossils (mollusks, Radiolaria, planktonic and benthic Foraminifera and Ostracoda) found in the four loess profiles located respectively at Heishigou and Beizhuang Villages on Daheishan Island in the Miaodao Islands in the Bohai Straits, and Daweijia and Yujiawaizi Villages in Jinzhou County, Liaodong Peninsula, the distribution and abundance variation of the fossils in vertical profiles are studied, the source of coastal loess is probed and the relationship between loess deposition and paleoclimatic environment as well as sea-level changes is discussed.

CHARACTERISTICS,ORIGIN AND EVOLUTION AGES OF AEOLIAN SAND IN THE SAHELIAN REGION OF MALI

The Sahelian region of Mali is one of the areas seriously affected by sandy desertification in the world. Widely distributed aeolian sand lays a material basis for the development of sandy desertification. Aeolian sand in the region is dominated by fine sand, followed by very fine sand. Sand materials contained in various sand dunes are different in grain size to a certain extent and the mineral compositions of dune sand are dominated by stable and extreme stable minerals, with high stability and maturity. Aeolian sand in the region mainly comes from the reactivation of ancient sand dunes, the transportation of recent runing water and the sand supply of dry lakes and arroyos. Since the Pliocene this region has experienced four major evolution periods of aelian sand, namely from the Pliocene to the early Quaternary, last glacial period, the Holocene and present.