bluuebunny/crossref_metadata_2025 huggingface dataset:
Geochemical Exploration on the Stream Sediments of Gabal El Mueilha Area, Central Eastern Desert, Egypt: An Overview on the Rare Metals
Authors: OBEID Mohamed , ALI Mohasen , MOHAMED Nabawia
Published: November 2008

Abstract: El Mueilha area consists of post‐collision granitic rocks intruding Pan‐African metasediments, metavolcanics and granodiorites. Tin mineralization in Gabal El Mueilha is either of vein type or disseminated in the greisenized and albitized parts of the granitic rocks. Cassiterite and wolframite‐bearing quartz veins also characterize a small intrusion of muscovite granite at El Mueilha tin mine area. Detailed geochemical prospecting for the rare metals Sn, Nb, Be, Li, U, Th and some other trace elements was carried out at Gabal El Mueilha area using stream sediments survey. Sixty‐seven stream sediment samples were collected from the main drainage patterns of the study area. Statistical parameters were calculated for the analyzed elements. The sought elements Sn, Nb, Be and Li have relatively high background values in the studied sediments. This may reflect the role of the pathfinder elements (Nb, Be and Li) during secondary dispersion survey for Sn mineralization.

Geochemical maps were constructed to delineate anomalous areas with abnormally high rare metal contents. The anomalous Sn, Nb and Be areas are mainly encountered in the main stream draining the mineralized zones of El Mueilha tin mine and near the SW albitized parts of the post‐collision granite. Correlation coefficient matrices show significant positive relation between Sn and the rare metals group (Nb, Rb and Li) at 99 % significant level. R‐mode factor analysis for the concerned elements yields five factor–model.
Thermochronology for the Granitic Pluton Related to Lead‐Zinc Mineralization in Tsushima, Japan
Authors: IKEMI Hiroaki , SHIMADA Nobutaka , CHIBA Hitoshi
Published: November 2008

Abstract: K–Ar datings and oxygen isotope analyses revealed a cooling history of the Uchiyama granitic pluton, which is genetically related to the Pb‐Zn deposits (Taishu mine) in the Tsushima Islands, Japan. The pluton intrudes into the Paleogene Taishu Group to form the biotite‐hornfels zone, while the Taishu vein‐type Pb–Zn deposits occur in fissures developed in the non‐hornfels zone about 1 to 3 km westward from the contact. Amphibole and biotite K‐Ar ages of the pluton have a wide range from 19 to 13 Ma. Oxygen isotopes of the biotite and coexisting quartz grains indicate that isotopic exchange reactions have occurred under subsolidus conditions, and that the K‐Ar ages are affected by various cooling rates in the pluton. The mineralization age of the Taishu ore deposits is obtained for the first time to be 15.40.8 Ma by a K‐Ar age of 2M1–muscovite in a calcite–quartz–muscovite–chlorite veinlet of the Shintomi orebody. Whole rock K‐Ar ages of biotite‐hornfels near the pluton represent similar ages to the ore deposits. Using blocking temperature calculated from reported diffusivity for argon, the pluton was cooled from 560 to 350C in the period of 17 to 14 Ma. The vein formation took place after the time when temperature in wall rocks of the pluton had dropped below the brittle‐plastic transition (about 400C). These results imply that the cooling of the pluton has caused injection of magmatic fluids into meteoric hydrothermal systems, and the Pb‐Zn mineralization has occurred due to this mixing at the age of about 15 Ma.
Further Occurrence of Brown Ores in Kuroko‐type Deposits in Japan
Authors: IMAI Akira , ISHIZUKA Osamu , YAMADA Ryoichi , MIYAMOTO Hiroshi
Published: November 2008

Abstract: The occurrence of so‐called brown ore from the Kuroko‐type deposits in Japan was examined. Brown ore specimens from the Kannondo, Inarizawa, Matsumine, Fukazawa, Uchinotai, Kosaka (orebody unknown) and Nurukawa deposits have been found in the ore collection stored by Dowa Mining Co. Ltd. and the subsidiary companies. In addition, occurrences from the Fukazawa, Matsumine, Ezuri, Shakanai, and Ginzan deposits were previously reported. The brown ore is characterized by its color and by its higher Ag concentration (up to around 2,400 g/t) than ordinary black ores. This type of ore occurs commonly in the Kuroko‐type deposits in Japan, whereas its extent is limited. The brown ore is a type of Au‐rich massive sulfide ore formed in submarine hydrothermal system.
Gold Content in Siliceous Deposits Formed from Acidic and Iron‐rich Geothermal Waters at Hatchobaru, Central Kyushu, Japan
Authors: UCHIDA Akiko , YOKOYAMA Takushi , WATANABE Koichiro , IZAWA Eiji
Published: November 2008

Abstract: The gold content in siliceous deposits formed from geothermal waters at the Hatchobaru geothermal power station in central Kyushu, Japan, was determined by inductively coupled plasma quadrupole mass spectrometry (ICP–MS). It ranges from 1.3 to 4.6 mg/kg. The highest gold content was obtained from the siliceous deposit formed from acidic waters. In this siliceous deposit, hydrous iron(III) oxide of amorphous state is a major constituent, suggesting that hydrous iron(III) oxide might play an important role when gold is concentrated into siliceous deposits formed from acidic and iron‐rich geothermal waters.
Geo–tectonic Position of Tin Polymetallic Mineralization Zone in the Southern Da Hinggan Mountains Area, Inner Mongolia, China: An Introduction to This Special Issue
Authors: SUN Shihua , AKIYAMA Shin–ichi
Published: November 2008

Abstract: As a part of the main activities of Japan‐China technical cooperation project, a test survey area, approximately 5,000 km2, was established for the implement of its geological and geochemical research program. A major mineralization zone called Huanggang–Ganzhuermiao–Wulanhaote Sn‐Cu polymetallic mineralization zone is recognized in the southern Da Hinggan Mountains area. The southern half of this zone is known as the sole Sn‐mineralization zone in North China. The survey area lies in this prominent zone. As the most of the papers presented in this issue have concerns to the geology and mineralization in this survey area, this report was prepared to introduce geo‐tectonic situation of the Sn‐Cu polymetallic mineralization zone in the Inner Mongolia orogenic belt. The belt is divided into four tectonic facies (from NW to SE); I: Wuliyasitai volcano‐plutonic zone, II: Hegenshan ophiolite mélange zone, III: Sunitezuoqi volcano‐plutonic zone, IV: Wenduermiao ophiolite mélange zone. The subject Sn‐Cu polymetallic mineralization zone is situated in the southeastern part of the Sunitezuoqi magmatic zone. About this Sunitezuoqi magmatic zone, three geo‐tectonic characteristics are pointed out. In late Carboniferous to early Permian period, subduction of Hegenshan oceanic crust occurred, which accelerated volcano‐plutonic activities and brought about basic to intermediate volcanic rocks of tholeiitic to calc‐alkaline series represented by Dashizhai Group in the Sunitezuoqi magmatic zone. Late Jurassic to early Cretaceous acidic rocks representing the most culminated volcanism and plutonism in Mesozoic era in the Da Hinggan Moutains area are distributed very extensively in and around the Sn‐Cu polymetallic mineralization zone. The Proterozoic metamorphic basement rocks called Xilinhaote complex are distributed close to the mineralized area in the Sunitezuoqi magmatic zone.

Although the real mineralization was known associated with Mesozoic acidic to intermediate volcano‐plutonic activities, it is thought that the lower Permian Dashizhai volcanic rocks and pre‐Cambrian basement rocks might have played certain significant role in the process respectively of extraction of elements and formation of the magma favorable for such mineralization in the Sunitezuoqi magmatic zone. It would be necessary to give further considerations to these three geological units in relation to the Sn‐Cu polymetallic mineralization.
The Upper Permian Sedimentary Facies and Its Role in the Dajing Cu‐Sn Deposit, Linxi County, Inner Mongolia, China
Authors: QIN Gongjiong , KAWACHI Yosuke , ZHAO Liqing , WANG Yongzheng , OU Qiang
Published: November 2008

Abstract: Exhaustive investigations were launched for confirming the upper Permian host rocks of the Dajing Cu‐Sn Deposit, probing into the possibility that Dajing is a Sedex type deposit during cosedimentation, complementing the deficiency of previous researches and going further into substantiating the role of the upper Permian strata in the control of ore distribution. After more than two years work, we reclassified the sedimentary facies in the Dajing area and its periphery as shallow fresh water lake and delta. Indicative sedimentary structures, such as ripple marks, rain marks, and mud cracks combined with contemporary fossils, were revealed. Having measured the flow directions, performed chemical comparison, and analyzed various sediments from sourceland in the Dajing area by XRF, we consequently redivided the strata into four sedimentary members, among which P2l1 and P2l2 were concluded as significant ore‐hosted strata. The upper Permian basin was a lateral rift basin. The water and sediments in the basin are much deeper and thicker in the north than those in the south.

The indicators of special sedimentary facies, such as gravity flow, brine pool and synchronogenic stratiform structure of the ore cannot be found in the Dajing area. There was no growth fault, assemblage of sulfide and sulfate, and no zonation as well.

On the basis of study in this area, taking into account the paleosedimentary environment as capriciously flowing shallow lake, which approximated the state of oxidation, we figured that the paleogeography made it prohibitively difficult to form stratiform sulfide deposits which are prone to form in deoxidized environment. It can be ruled out the possibility that the Dajing deposit is a syngenetic deposit during sedimentation.
Geology and Mineralization at the Dajing Tin‐polymetallic Ore Deposit, Inner Mongolia, China
Authors: WANG Yu Wang , WANG Jing Bin , UEMOTO Takeshi , WANG Li Juan
Published: November 2008

Abstract: Dajing is a large‐scale tin–polymetallic ore deposit in north China with Sn, Cu, Pb, Zn, Ag, and minor elements such as Co and In. The deposit is controlled by a passage‐host structure system. Two groups of NE direction faults such as F2 and F1 are characterized by sinistral and multiphase activities, and the syn‐ore NE faults with their derivative faults nearly in N‐S direction constitute an important structure system as channelway for ore fluid. Around F2 fault (mineralization center), metallic elements display horizontal zoning outwards from Sn, Cu to Cu, Sn, Pb, Zn, Ag and to Pb, Zn, Ag. Controlled by sinistral pull‐apart vein system, the WNW direction host structure yielded the ore vein to “W” shape on horizontal plan while to staircase shape on vertical profile. Multiperiodic activities of the host structures system lead to multistage of ore mineralization. Four mineralization stages are recognized in the main mineralization, i.e. 1) cassiterite–arsenopyrite–quartz stage, 2) cassiterite‐sulfide (or Cu–poly–metallic mineralization) stage, 3) massive pyrite stage, and 4) galena‐sphalerite stage. Besides, fluid activities are identified here at the pre‐mineral stage of the formation of quartz veins and sheared deformation, and at the post‐mineral stage of quartz–calcite–fluorite deposition.

The earlier tin‐rich ore solution raised from NE faults and its nearly N‐S derivatives filled the NW‐WNW direction fractures, and formed tin ore veins. Subsequent mineralization of Cu‐polymetallic stage, pyrite stage and galena‐sphalerite stage, overlapping on the same fracture system, sequentially expanded outwards from the fractures, and produced different kinds of ore types and mineralization zoning.
Petrogenetic and Metallogenetic Background of the Dajing Cu–Sn–Ag–Pb–Zn Ore Deposit, Inner Mongolia, and Characteristics of the Mineralizing Fluid
Authors: LIU Wei , LI Xin–Jun , TAN Jun
Published: November 2008

Abstract: The Dajing Cu–Sn–Ag–Pb–Zn ore deposit, Inner Mongolia of China, is a fissure‐filling hydrothermal ore deposit that occurs within the Upper Permian Linxi group. No magmatic pluton and volcanic rocks outcrop on the surface of the deposit. Most of ore veins show clear‐cut boundary with country rocks. Wallrock alterations that include silicification, carbonation, chlori–tization, and sericitization are generally weak and occur in the close vicinity of ore veins.

Mineralization is divided into three stages: (1) cassiterite–arsenopyrite–quartz stage, (2) sulfide stage, and (3) Pb–Zn–Ag–carbonate stage. These mineralization stages have distinct ranges of homogenization temperatures, 290–350C for Stage 1, 260–320C for Stage 2, and 150–250C for Stage 3. However, salinities for Stages 1, 2, and 3 overlap and range between 2.2 and 10.4 wt % NaCl equivalent. The dD values relative to V‐SMOW of inclusion water from quartz are lower than –88% and centered at –100 to –130%. The δ34S values relative to CDT of sulfide ore minerals and δ13C values relative to PDB of carbonate gangue minerals, vary from –0.3 to +2.6%, and from –7.0 to –2.9%, respectively. Integrated isotopic data point to two major contributions to the mineralizing fluid that include a dominant meteoric‐derived water and the other from hypogene magma for sulfur and carbon species.

Analyses of inclusion gas and liquid compositions are performed. The H2O and CO2 are the two most abundant gaseous components, whereas SO42‐ and Cl‐, and Na+, Ca2+, and K+ are the major anions and cations, respectively. A linear trend is shown on the gaseous H2O versus CO2 plot. Phase separation is excluded as cause for the trend on the basis of isotope data and fluid inclusion microthermometry. In addition, a weak wallrock alteration does not support fluid‐rock interaction as an efficient mechanism. Hence, the linear H2O–CO2 trend is interpreted in terms of absorption or dilution of CO2–dominant magmatic vapor by meteoric‐derived water. Cooling effects resulting from dilution may have caused precipitation of ore minerals.

Major and trace element compositions of regional granites show a high‐K calc–alkaline characteristics and an arc–affinity. Lead isotopic compositions of galena samples from the Dajing deposit exhibit elevated U/Pb and Th/Pb ratios. These characteristics indicate a common source of supra subduction zone mantle wedge for regional granites and metals from the Dajing deposit.
Sulfur, Carbon and Lead Isotope Studies of the Dajing Polymetallic Deposit in Linxi County, Inner Mongolia, China – Implication for Metallogenic Elements from Hypomagmatic Source
Authors: CHU Xuelei , HUO Weiguo , ZHANG Xun
Published: November 2008

Abstract: The Dajing Cu‐polymetallic ore deposit in Linxi county, Inner Mongolia Autonomous Region, China, is economically a valuable Cu–Sn–Ag–Zn–Pb deposit in the southern section of the Da Hinggan metallogenic province. For the analyzed 23 samples of sulfide minerals, including chalcopyrite, pyrite, sphalerite and galena, the δ34S values range from –1.8 to +3.8 % with an average of +0.65 %. The narrow distributions of the δ34S values with +1 % peak value, including the published data, and the δ13C values around –5 % indicate that the sulfur and carbon of the hydrothermal fluids are derived from a hypomagmatic source, and exclude the possibility that the hosted strata, i.e., the Upper Permian Linxi Formation, provided certain amounts of sulfur and carbon.

The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of sulfide ores range respectively within 18.257‐18.368, 15.476‐15.609, and 37.916‐38.355 with the model ages of 122–209 Ma. The black shale, however, contains higher radiogenic lead with the 206Pb/204Pb ratios of 18.473‐20.156, differing from the ores. However, the 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of the ore, basaltic porphyrite and feldspar leads are similar, and lie on the same lines in the diagrams of 208Pb/204Pb vs. 206Pb/204Pb and 207Pb/204Pb vs. 206Pb/204Pb. The fact that these mixing lines are composed of the two end members, the mantle and orogenic belt, strongly supports that all the metallogenic elements were carried by the hypomagma mixing the matters of the mantle and orogenic belt prior to the Mesozoic. Therefore, the Dajing ore deposit is a typical mag–matic–hydrothermal vein type ore deposit associated with subvolcanic rocks.
Dashuigou Tellurium Deposit in Sichuan Province, China: S, C, O, and H Isotope Data and Their Implications on Hydrothermal Mineralization
Authors: MAO Jingwen , WANG Yitian , DING Tiping , CHEN Yuchuan , WEI Jiaxiu , YIN Jianzhao
Published: November 2008

Abstract: Dashuigou, a unique tellurium‐dominated deposit over the world, is located in the western margin of the Yangtze cra‐ton in southwestern China. It is characterized by high‐grade tellurium accompanied by bismuth, gold, silver, and sulfur, and occurs in the area of less than one km2. The mineralization is divided into three stages, i.e. (1) tellurium‐bearing pyrrhotite–pyrite stage, (2) tetradymite stage, and (3) auriferous quartz veins stage. Tellurium mineralization coexisting with bismuth, silver, selenium, and gold predominantly develops in the stage 2, while the stage 1 is enriched only in sulfur and iron, and the stage 3 is very weakly mineralized with gold.

The δ34S values of sulfides in the ore of the deposit vary in a narrow range of –3.1 ‐ +2.8 per mil with –3.1 ‐ +2.8 per mil for the stage 1 and –0.5 ‐ +2.1 for the stage 2, showing the isotopic characteristics of mantle derived sulfur. The δ13C values of vein dolomites vary from –5.3 to –7.2 per mil, with –5.3 ‐ –6.6 per mil for the stage 1 and –5.3 ‐ –7.2 per mil for the stage 2, which are significantly different from those of surrounding Triassic marble with δ13C values of –0.3 ‐ +2.8 per mil, and show characteristics of mantle derived carbon. The δ18O values of vein dolomites range from +10.2 to +13.1 per mil, which are higher than those of carbonatite, but lower than those of the marble. Their corresponding δ18Owater values are +0.6 ‐ +3.9 per mil, with +2.7 ‐ +3.8 per mil for the stage 1 and +0.6 ‐ +3.9 per mil for the stage 2. The data implies that these vein carbonates were formed by the mixing fluids of magmatic or mantle source with meteoric or formation water. The δ18O values of ore‐forming fluids responsible for the formation of vein quartz are estimated to be +3.2 to +6.8, the δD values of inclusion fluids of the quartz are measured to be –54 to –82 per mil. All those stable isotopic data suggest the involvement of the fluids from mantle and/or mantle‐derived magmas through fault system in the forming process of the Dashuigou tellurium deposit.
Geochemical Investigations of Stratabound Gunga Barite Deposits of Khuzdar (Balochistan), Pakistan
Authors: HUSAIN Viqar , KHAN Hameedullah , GERMANN Klaus , ZAK Karel
Published: November 2008

Abstract: The Gunga barite deposits occur in carbonate clastic marine sequence of Jurassic age. These rocks are widely spread in Khuzdar‐Lasbela belt which host important stratabound barite and zinc‐lead deposits of Pakistan. These rocks are intricately folded and extensively faulted. The Gunga are low temperature hydrothermal deposits occurring as a series of disconnected lenses a few meters thick. Two mineralized horizons are recognized: barite in the upper zone, sphalerite and galena in the lower zone. Four types of barite mineralization occurs in Gunga stratabound replacement associated with 1) fracture filling, 2) open space fillings in solution collapsed breccia, 3) replacement in fault, and 4) veinlets associated with all these three types. The wall rocks of the Gunga deposits have also been altered by silicification, leaching and ferruginization.

The sulfur isotope values of most of the Gunga barite samples range from 23.8 to 27.8 per mil with an average of 26.4 per mil, which is very close to the average of isotopic values of epigenetic carbonate hosted Late Paleozoic Missouri barite deposits. The Gunga like other barite and sulfide deposits of Khuzdar‐Lasbela belt are Mississippi Valley type, stratabound and of replacement origin precipitated from connate brines expelled during the incipient rifting of India from Gondwana land in the Late Jurassic and Early Cretaceous periods. The low content of copper, lead and zinc in the Gunga barite deposits suggests that these deposits were not formed in proximity to an igneous source of the ore solution.

The Gunga deposits are epigenetic and stratabound as their mineralization is structure controlled. There is an evidence of transgressive nature of host rock and wall rock alteration which are absent in stratiform or bedded deposits.
Negative Ce Anomaly in the Indian Banded Iron Formations: Evidence for the Emergence of Oxygenated Deep‐Sea at 2.9‐2.7 Ga
Authors: KATO Yasuhiro , KANO Takashi , KUNUGIZA Keitaro
Published: November 2008

Abstract:Major and rare earth element contents are reported for Late Archean banded iron formations (BIFs) in the Bababudan Group of the Dharwar Craton, South India. The BIFs are mostly composed of SiO2(average1ρ = 54.88.1 wt%) and Fe2O3* (44.38.2 wt%). The Al2O3and TiO2contents are remarkably low, suggesting that detrital components were starved during the BIF deposition. The BIFs have a LREE‐enriched pattern with a relatively high (La/Yb)N(6.644.07). Total REE concentrations (RE) vary from 5.2 to 65.3 ppm. The REE patterns are characterized by the presence of a very large negative Ce anomaly (Ce/Ce*: 0.13‐0.83) and a positive Eu anomaly (Eu/Eu*: 0.96‐2.45). The Eu/Eu* decreases and (La/Yb)Nincreases with a increase of RE. These correlations of REE indices are similar to those of modern hydrothermal iron‐rich sediments near a mid‐ocean ridge (MOR). Greenstones associated with the BIFs have MORB‐like geochemical features. These geochemical and geological lines of evidence indicate that the depositional site of the BIFs was remote from a continent and/or island arc and that the BIFs werein situhydrothermal sediments near a MOR. A striking negative Ce anomaly in the BIFs indicates that oxygenated deep‐sea environments emerged at 2.9‐2.7 Ga. The existence of contemporaneous Mn deposits in the Dharwar Craton supports this assertion. Our scenario of oxygen in the Earth's surface of the Late Archean is different from long‐held notion that the atmosphere and ocean were persistently anoxic throughout the Archean.
Benthic Foraminifera in Siliceous Black Ore from the Ezuri Kuroko Deposit, Hokuroku District, Japan
Authors: KOMURO Kosei , AOKI Naoaki , KAJIWARA Yoshimichi
Published: November 2008

Abstract: Abundant benthic foraminifera have been identified in thin sections of the siliceous black ore in the Ezuri Kuroko deposit, Hokuroku, Japan. By treating samples with conventional hydrofluoric acid digestion techniques, sponge spicules and radiolaria have also been recognized in the residue. Under microscopic observations, 94 individual foraminiferal specimens have been detected. However, as it is difficult to identify species or genera by means of microscope observations alone, only a small number of genera have been identified based on morphology. The foraminiferal assemblage is composed predominantly of agglutinated species (83%) with subordinate calcareous species (17%), and is assigned to the Cyclammina Assemblage based on the preponderance of Cyclammina (57%). The foraminifera are generally well preserved within micro‐crystalline to cryptocrystalline quartz, and exhibit no obvious features related to compaction or secondary deformation.

Textural observations suggest that the siliceous component of this rock was not derived from an allochthonous block but instead constitutes autochthonous proto‐Kuroko sediment. The Cyclammina Assemblage in the ore is different from recently described foraminiferal assemblages in the vicinity of present deep‐sea hydrothermal vents, but is identical to those found in black shales of the Onnagawa to Funakawa stages in the Green Tuff region. The proto‐Kuroko sediment is assumed to have been deposited in an oxygen‐deficient environment within a closed, deep‐seated basin.

The existence of siliceous microfossils suggests that the silica in the siliceous ore did not originate from silica sinter deposits produced by submarine hydrothermal activities, but from a biogenic siliceous ooze, probably composed of diatoms.

Sulfide mineralization in the interstices of some of the microfossils is inferred to relate primarily to bacterial sulfate reduction associated with the decomposition of organic matter. The later sulfide mineralization associated with larger crystals (which contain fluid inclusions with homogenization temperatures of approximately 250C) cuts across the siliceous masses and foraminiferal septa, and may have been formed after consolidation of the siliceous ooze, accompanying the formation of acidic intrusive rocks during the late Onnagawa stage.
Unique Geochemistry of Sedimentary Iron Deposit Formed by Biologically Induced Mineralization
Authors: KATO Yasuhiro , IKEDA Tomoko , MORIGUCHI Emi
Published: November 2008

Abstract: Major, trace, and rare earth element contents were determined for sedimentary iron ores from the Gunma iron deposit. The deposit was precipitated from a spring water on the hillside of the active Kusatsu‐Shirane Volcano. The ores are mainly composed of goethite and jarosite with various proportions of silicified andesitic detritus. Microbial fossils are often preserved well in goethite‐rich ores. Goethite was likely precipitated by both inorganic and biogenic (biologically induced mineralization; BIM) processes, whereas jarosite was precipitated inorganically from the spring water. Si, Ti, Al, Mn, Mg, Ca, Na, Co, Rb, Y, Zr, Nb, Hf, Ta, U, and middle‐heavy REEs (Sm‐Lu) in the ores are dominantly derived from a detrital component (silicified andesitic rocks). On the other hand, Zn and V are likely to have been inorganically coprecipitated with goethite. Preferential uptake of P, Sc, Cu, Mo, Ba, Th, and light REEs occurs in the BIM ores. Unique enrichment of these elements is a promising indicator of biomineralization for ancient sedimentary iron deposits.
Geochemical and Nd, Sr Isotopic Study of the Post‐Orogenic Granites in the Yidun Arc Belt of Northern Sanjiang Region, Southwestern China
Authors: QU Xiaoming , HOU Zengqian , ZHOU Shugui
Published: November 2008

Abstract: In the arc (basin)–back area of the Yidun arc belt in the north segment of the Sanjiang tectonic zone, southwestern China, there occurs a post‐orogenic granite belt extending for more than 300 km in NNW direction. It strides across two different tectonic units of the arc (basin)–back area and the subduction area, and is accompanied by extensive Ag‐Sn polymetal–lic mineralizations. More than ten granite bodies have very similar geochemical characteristics: high SiO2 (73.8–76.3 wt%) and K2O+Na2O (7.16‐8.41 %), and low Al2O3 (11.9–13.6 %), CaO (0.46‐1.54 %) and MgO (0.16‐0.61 %), as well as high enrichment of Nb, Ta, Ga and Y, and strong depletion of Sr and Eu. Most of these features are peculiar to A‐type granite. Rb‐Sr and 40Ar/39Ar isotopic dating results indicate that the formation ages of the granites decrease from 103.7 Ma of the north end to 75.2 Ma near the south end, and that the magmatism became younger from north to south. The tectonic environment analysis clearly reveals that they were formed in post‐orogenic within–plate extension settings. The magma genesis was controlled by a united crustal extension regime after the arc‐continent collision. The granites have low Nd values ranging from –4.96 to –8.40, whereas the Sr values vary greatly ranging from –31.7 to 296, reflecting that the source composition transited from mantle – differentiated igneous rocks in the north to basement – dominated metamorphosed sedimentary rocks in the south. Under high temperature and water‐absent conditions, the anatexes of the crustal rocks made a great amount of plagioclase separated from melts and left in magma sources. Through this mechanism, the post‐orogenic granites took geo‐chemical characteristics such as low Al2O3 and CaO, and strong depletion of Sr and Eu.
Structural CO2 in the Apatite of the Late Cretaceous Phosphorite Resources in Egypt: Effect on the Crystal Chemistry and Geologic Implications
Authors: BAIOUMY Hassan M.
Published: November 2008

Abstract: Phosphorite deposits in Egypt, known as the Duwi Formation, are a part of the Middle East to North Africa phospho‐genic province of late Cretaceous to Paleogene age. Based on the petrographical observation, the phosphatic grains in the phosphorites are classified into phosphatic mudclasts and phosphatic bioclasts. Both of them are composed of francolite. The structural CO2 contents in the francolite range from 3.3 to 7.2 % with an average of 5.3 %. Results indicated that the substitution with CO32‐ of PO43‐ in the francolite decreases the unit cell volume and a‐cell dimension, and increases the c/a ratio. Effect is more obvious in the a‐cell dimension; therefore, it is more significant in distinction between the different apatite species.

Lack of covariance between structural CO2 contents in the francolite and the carbonate minerals contents may render the supposition that the phosphorites formed as a result of replacement of preexisting calcareous sediments is doubtful. Similarity in CO2 content in both weathered and fresh samples indicates that the structural CO2 content in the phosphorites is not affected by weathering, and reflects the conditions and CO2 concentration of the depositional environment. Similarity in mineralogy and CO2 contents in the different phosphatic grains and higher CO2 content in the Egyptian phosphorites compared with the authigenic phosphates of Peru margin, which formed by the same mechanism as the Duwi phosphorites, suggest that the phosphatic grains in the Duwi Formation were francolitized during diagenesis by introducing CO2 from the surrounding pore water and diagenesis took place at an elevated temperature. Scattered values of structural CO2 contents suggest the reworking origin of the phosphatic grains in the late Cretaceous phosphorites in Egypt.
The Fluid Evolution Related to Talc Mineralization in the Hwanggangri Area, South Korea
Authors: SHIN Dongbok , LEE Insung
Published: November 2008

Abstract: Scores of talc deposits distributed in the Hwanggangri Mineralized Zone, South Korea are interpreted to have resulted from the contact metamorphic process related to the igneous intrusion of the Muamsa Granite. Talc usually occurs as an alteration product from tremolite, which is crystallized during the prograde stage. It commonly forms fine–grained, fibrous aggregates, or pseudomorphs after tremolite, and abundant tremolite is included as impurities in the talc ore. Quantitative X‐ray diffraction analysis has shown that the ores can be divided into three types depending on the concentrations of talc; talc‐tremolite ore (talc > 50 %), tremolite‐talc ore (10 % < talc < 50 %), and tremolite (talc < 10 %) ores. Oxygen isotope compositions of those talc ores become higher from 10.9–12.1 through 11.6–12.3 to 11.9–13.2% with increasing tremolite concentrations, while hydrogen isotope compositions are not so variable, –73 to –69%. The high value of the calculated δ18OH2O of the fluids equilibrated with the tremolite may have resulted from the mixing of magmatic water with 18O–enriched CO2 evolved from the decarbonation reaction during the prograde stage. However, as the decarbonation reaction ceased during the retrograde stage, the inferred oxygen isotope compositions of talc‐forming fluids show similar values to those of the igneous fluids.
Possible Carbonate Origin of Ore Sulfur from Geumseong Mo Deposit, South Korea
Authors: ISHIHARA Shunso , KAJIWARA Yoshimichi , JIN Myung–Shik
Published: November 2008

Abstract: In order to know the cause of the high δ34S values of the Korean ore deposits (Ishihara et al., 2000), Geumseong molybdenum skarn deposit and related Jurassic granitoids and Cambro‐Ordovician carbonates were selected for the δ34S analyses. Two sulfide samples occurring in hydrothermal veins in fresh granitoids quarry at Songhaksan yielded δ34S values of +6.9 and +8.8 permil. These are slightly higher than +5.3 permil δ34S of the averaged rock sulfides for the Jurassic Daebo granitoids. Pyrite and molybdenite from the Geumseong deposit vary from +8.6 to +11.5 permil (average + 10.7 permil). The intruded carbonates contain very low amount of SSS (structurally substituted sulfate) as 2.9 to 8.1 ppm with high δ34S values between +28.8 and + 40.0 permil, and sulfides sulfur of 52 to 779 ppm with variable δ34S values between +3.2 and +22.5 per–mil. It is concluded that sulfur of the host carbonates was extracted and migrated into the skarn deposit at the time of the granitoid intrusion and the related hydrothermal convection, on the basis of the location of the skarn deposit occurring between the carbonates and Jurassic granitoids, and of very low contents of SSS sulfur in the carbonates. A part of SSS possibly contaminated into the Jurassic granite.
Exploration Techniques at the Thorn Ag‐Au‐Cu High‐Sulfidation Epithermal Prospect, Northern British Columbia, Canada
Authors: Awmack Henry
Published: November 2008

Abstract. The Thorn prospect is an El Indio‐style high‐sulfidation epithermal prospect in a little‐explored belt of Late Cretaceous subaerial volcanics and subvolcanic intrusions in northwestern British Columbia, Canada. More than 30 massive sulfide (pyrite‐enargite‐tennantite/tetrahedrite) veins, quartz‐sulfide (quartz‐pyrite‐enargite‐tennantite/tetrahedrite) veins and quartz‐vuggy silica‐alunite veins/breccias fill ENE fractures and faults over an area of 1,600 times 1,900 m. They are hosted within a Late Cretaceous feldspar‐quartz‐biotite granodioritic porphyry stock and flanked by alteration envelopes a few meters to tens of meters wide: an inner envelope of intense sericite‐clay‐pyrite and an outer one of weak clay‐sericite‐chlorite. Where several veins are close together, the sericite‐clay‐pyrite alteration envelopes coalesce into zones up to 150 m wide.

The most successful exploration techniques have been prospecting, silt and soil geochemistry, airborne magnetic and electromagnetic surveys and diamond drilling. Silt and soil geochemical anomalies for Au, Ag, As, Cu, Pb, Sb and Zn mark the known veins and indicate prospective areas where veins have not yet been discovered. Magnetics and resistivity outline the gross property‐wide structure and lithologies. Most of the sericite‐clay‐pyrite alteration and known veins are outlined by the <264 ohm‐m resistivity contour, which covers an area of 800 times 2,300 m. Weak EM conductors are thought to represent undiscovered massive sulfide and quartz‐sulfide veins, and their flanking sericite‐clay‐pyrite alteration.
Victoria Carbonate‐Base Metal Gold Deposit and Its Significance in the Mankayan Mineral District, Luzon, Philippines
Authors: Sajona Fernando G. , Izawa Eiji , Motomura Yoshinobu , Imai Akira , Sakakibara Hiroyuki , Watanabe Koichiro
Published: November 2008

Abstract. The Victoria gold deposit is a low‐sulfidation style epithermal carbonate‐base metal gold deposit discovered in 1995 in the Mankayan mineral district, northern Luzon, Philippines. It occurs just south of a high‐sulfidation copper‐gold orebody (Lepanto enargite deposit) and a porphyry copper‐gold orebody (Far Southeast (FSE) deposit). Radiometric dating of the Victoria mineralization yields ages from 1.6 to 1.1 Ma, similar to ages of the Lepanto enargite deposit. Mineralogical, geochemical, fluid inclusion and sulfur isotope studies suggest that the Victoria deposit is not directly related to the late stage of hydrothermal activity that produced the FSE porphyry copper‐gold and the Lepanto enargite deposits. The hydrothermal fluids from which Victoria was formed appear to have been derived from the south, and not from the FSE intrusive center to the northeast. This would suggest a regional south to north hydrothermal gradient, consistent with the similar flow within the FSE porphyry‐Lepanto enargite system. On a district scale, structures similar to those of the Victoria deposit in trend and nature would be highly prospective, especially if they occur north of identified plutons and volcanic centers.
Hydrothermal Gold Mineralization at the Rodnikovoe Deposit in South Kamchatka, Russia
Authors: Takahashi Ryohei , Matsueda Hiroharu , Okrugin Victor M.
Published: November 2008

Abstract. The Rodnikovoe gold deposit situated in a presently active hydrothermal system located north of the Mutnovsko‐Asachinskaya geothermal area in southern Kamchatka, Far Eastern Russia, consists of typical low‐sulfidation quartz‐adularia veins in a host rock of diorite. The age of the mineralization was dated by the K‐Ar method as 0.9 to 1.1 Ma based on adular‐ia collected from the veins. Representative ore minerals in the deposit are electrum, argentite, aguilarite, polybasite, pearceite and lenaite. Dominant alteration minerals are adularia, α‐cristobalite, chlorite, illite and kaolinite. Hydrothermal solutions of neutral pH were responsible for the mineralization, which is divided into six stages defined by tectonic boundaries. Gold mineralization occurred in stages I and III. Hydrothermal brecciation occurred during stages III, IV and VI. Stages II, IV, V and VI were barren. The estimated ore formation temperature based on a fluid inclusion study is 150 to 250 °C at a depth of approximately 170 m below the paleo‐water table. Boiling of hydrothermal fluids is hypothesized as the cause of the intermittent deposition of gold ore. The sulfur and oxygen fugacities during the deposition of anhydrite prior to the hydrothermal brecciation were higher than those during the gold mineralization stages. The occurrence in the hydrothermal breccia of fragments of high grade Au‐Ag and polymetallic ores suggests that higher grade mineralization of these metal ores might have occurred in a deeper portion of the deposit.
Association of Electrum and Calcite and Its Significance to the Genesis of the Hishikari Gold Deposits, Southern Kyushu, Japan
Authors: Imai Akira , Uto Tadakazu
Published: November 2008

Abstract. Mineral assemblage, precipitation sequence and textures of the gold‐bearing veins from the Hishikari epithermal vein‐type deposits, southern Kyushu, Japan, were examined. In addition, fluid inclusion microthermometry and carbon and oxygen isotopic compositions of calcite were determined. Calcite, and that replaced by quartz, were commonly observed throughout the precipitation sequence of the veins. Thus, calcite must be a more common gangue constituent initially than observed presently. Association of calcite and electrum is observed immediately subsequent to columnar adularia in some vein samples. In addition, close association of electrum with pseudo‐acicular quartz, and electrum with truscottite were observed. The initial coprecipitation of electrum and calcite might be a common phenomenon in the gold‐bearing veins at the Hishikari deposits.

The Th (homogenization temperature) data from the Honko‐Sanjin deposits are generally higher than those from the Yamada deposit. Samples that show association of calcite and electrum yielded higher Th (206–217°C, average) than the Th data from calcite associated with low‐grade Au ore or barren (180–204°C, average). The measured Tm (temperature of last melting point of ice) range from ‐0.4 to 0.0°C. The result suggests that the salinity of the hydrothermal solution was low during the precipitation both of calcite associated with Au mineralization and of barren calcite. Fluid inclusion evidence suggestive of boiling of hydrothermal solution for the precipitation of calcite was not recognized in the present work. The δ13C and δ18O values of calcite range from ‐10.8 to —4.7 % and from +3.2 to +15.2 %, respectively. The δ13C value of H2CO3 and the δ18O value of H2O in the hydrothermal fluids calculated assuming isotopic equilibrium with calcite using the temperature obtained by fluid inclusion microthermometry, range from ‐14.4 to ‐9.1 %, and from ‐6.2 to +5.5 %, respectively. Thus, the calculated δ18O values of H2O for calcite further confirm the presence of the 18O‐enriched ore fluids during the mineralization at the Hishikari deposits. The hydrothermal solution isotopically equilibrated with the sedimentary basement rocks was responsible for the gold mineralization associated with calcite.
Timing of Fracture Formation and Duration of Mineralization at the Hishikari Deposit, Southern Kyushu, Japan
Authors: Sekine Ryota , Izawa Eiji , Watanabe Koichiro
Published: November 2008

Abstract. The Hishikari epithermal gold deposit consists of the Honko‐Sanjin zone and Yamada zone. On the basis of observed crosscutting relationships of veins, vein system in the Hishikari deposit was classified into the early and late veins. They differ from orientation, width, control by unconformity, the amount of displacement and structural features, but have similarity in gold grade and Au/Ag ratios. K‐Ar ages are presented for the classified veins to clarify timing of fracturing and duration of mineralization.

Age determination revealed that the early veins in the Honko‐Sanjin zone range from 0.86 to 1.11 Ma and that the late veins range from 0.73 to 0. 84 Ma. The economically most important mineralization in the Hishikari deposit occurred around 0.90 Ma in a very short period (about 0.05 million years).

The distribution of mineralization age in the whole Hishikari deposit, occurrences of slickensides and ground water temperatures imply that mineralization lasted longer in the southern part of the deposit. As compared the early veins with late veins, structural changes including width, strike, dip and vein characteristics occurred at around 0.85 Ma.
Shear‐hosted Mesothermal Vein System in the Jiapigou Goldfield, Northeast China: Implication for Subsequent Exploration
Authors: Liu Hongtao , Liu Jianming , Sun Shihua , Zhai Mingguo
Published: November 2008

Abstract. The auriferous mesothermal lodes and veins occurred in the Jiapigou Goldfield, Jilin Province, Northeast China, are inevitably hosted by shear zones or fractures of varying orientations and magnitudes. Our recent study suggests that the Jiapigou major shear zone (JMSZ) ‐ a regional NW‐SE‐trending driving structure, played an essential role in the formation and localization of the shear‐hosted auriferous mesothermal systems. Regional dextral shearing of the JMSZ controlled the general occurrences and orientations of lodes and veins, and consequently, constrained the development of the internal structures, geometric details and final localization of lodes and veins. Therefore, the development and final localization of shear‐hosted gold system can be comprehensively recognized in terms of both the Riedel shear system theory and the effects of the regional prolonged progressive deformation of subhorizontally right‐lateral shearing. The lodes and veins belonging to “R‐” and “D‐shear” would tend to be much more stable along their strike and dip directions than those belonging to “T‐fracture” in the Riedel shear system. However, due to the prolonged progressive deformation, the original T‐fractures might undergo local strain localization and partitioning and finally were modified into hybrid fractures filled by auriferous quartz veins, as displayed by many typical lodes and veins occurred in the Jiapigou Goldfield. In order to refine predictive exploration modeling, it is important to understand the structural attributes, geometries, and final localization kinematics of ore‐hosting shears in a huge shear system as that developed in the Jiapigou Goldfield.
Sulfur Isotope Study of Precambrian Basement and Mesozoic Intrusive Rocks in the Southwestern Part of Ryeongnam Massif, Korea
Authors: Yoon Chung‐Han , Kim Cheong‐Bin , Lee Hyo‐Jae , Shimazaki Hidehiko
Published: November 2008

Abstract. Isotope composition of whole rock sulfur has been measured on 14 schists, 10 gneisses, 7 gabbroids, 7 granitoids and 2 sedimentary rocks, with of 9 sulfide (pyrite) sulfurs in gabbros and granitoids, from the southwestern part of the Ryeongnam Massif, Korea. The δ34S values of schists range from ‐4.6 to +6.1 % (average +0.9 %), those of gneisses from ‐4.0 to +0.8 % (‐1.9%), those of gabbroids from ‐2.3 to +3.7 % (+1.0 %), and those of granitoids from ‐5.9 to +3.2 % (‐1.9 %). The δ34S values of pyrite separated from gabbros and granitoids show rather heavier values ranging from +3.1 to +9.4 % with an average of+5.8%.

Though the δ34S values of whole rock sulfur give wide range of ‐5.9 to +6.1 %, the average of about ‐0.5 % is close to the mantle value. The granitoids sampled at the central parts of intrusive bodies or at the contacts with other plutonic rocks tend to show positive values, while those sampled near the boundary with basement rocks such as granitic gneiss and por‐phyroblastic gneiss show negative values. Though the reason of this tendency is not clear at present, the δ34S values of some granitoids in this area seem to represent possible influence by the assimilation of country rocks, particularly of gneisses.

Average isotopic compositions of ore sulfur from individual metal deposits in the studied area are summarized to have a range of+1.0 to +7.8 % with an average value of+3.2 %. The values are consistent with the previous finding that the ore sulfur isotopic values of the Ryeongnam Massif are the lowest among the four tectonic belts in Korea; Gyeonggi Massif, Ogcheon Belt, Ryeongnam Massif, and Gyeongsang Basin. This feature may reflect the isotopic compositions of plutonic rocks and basements in this area, which are characterized by relatively low values around zero permil.
Heavy Sulfur‐isotope Enrichment in Middle Miocene Onnagawa Mudstones in the Green Tuff Region, Northeastern Japan
Authors: Komuro Kosei , Kajiwara Yoshimichi
Published: November 2008

Abstract. Sulfur isotope ratios are analyzed for a series of mudstones in a successive section in the Taiheizan area in the central Green Tuff region, northeast Japan. The δ34S values for the Uyashinai Mudstone Member (Nishikurosawa stage), the Onnagawa Formation and the Funakawa Formation range from ‐45 to ‐14%, ‐20 to +4% and ‐30 to ‐10%, respectively. There is a marked positive shift in δ34S values at the Nishikurosawa/Onnagawa boundary and an upward δ34S‐decreasing trend in the Onnagawa and Funakawa Formations. The present data provides evidence for environmental change in the form of stratification of the seawater, initiated at the Nishikurosawa/Onnagawa boundary and persisting during deposition of the Onnagawa Formation, followed by gradual oxygenation during deposition of the Funakawa Formation.
An Unusual Texture: Skeletal Sphalerite in Pyrite from Dajing Tin‐polymetallic Deposit, China
Authors: Wang Yu Wang , Wang Jing Bin , Wang Li Juan
Published: November 2008

Abstract. Skeletal sphalerite with stellar, cruciform and snowflake‐like (or cauliflower‐like) shapes included in pyrite is widely found in the Dajing tin‐polymetallic deposit. It occurs only in chalcopyrite‐pyrite mineralization stage. The compositions of all sphalerites in the chalcopyrite‐pyrite stage are characterized by high Cu content (3.9 ‐ 7.0 wt% with a mean of 5.4 wt%), while the skeletal crystal sphalerite has higher zinc and cadmium contents, and lower copper and iron contents, compared with other sphalerites of the same stage. The skeletal crystal sphalerite in pyrite is possibly generated by exsolution.