bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
The Geochemical Context of Gas Hydrate in the Eastern Nankai Trough
Authors: Waseda Amane , Uchida Takashi 
Published: November 2008

Abstract. Geochemical studies for gas hydrate, gas and organic matter collected from gas hydrate research wells drilled at the landward side of the eastern Nankai Trough, offshore Tokai, Japan, are reported. Organic matter in the 2355 m marine sediments drilled to Eocene is mainly composed of Type III kerogen with both marine and terrigenous organic input. The gas hydrate‐bearing shallow sediments are immature for hydrocarbon generation, whereas the sediments below 2100 mbsf are thermally mature. The origins of gases change from microbial to thermogenic at around 1500 mbsf.Carbon isotope compositions of CH4 and CO2, and hydrocarbon compositions consistently suggest that the CH4 in the gas hydrate‐bearing sediments is generated by microbial reduction of CO2. The δ13C depth‐profiles of CH4 and CO2 suggest that the microbial methanogenesis is less active in the Nankai Trough sediments compared with other gas hydrate‐bearing sediments where solid gas hydrate samples of microbial origin were recovered. Since in situ generative‐potential of microbial methane in the Nankai Trough sediments is interpreted to be low due to the low total organic carbon content (0.5 % on the average) in the gas hydrate‐bearing shallow sediments, upward migration of microbial methane and selective accumulation into permeable sands should be necessary for the high concentration of gas hydrate in discrete sand layers.
Petrophysical Properties of Natural Gas Hydrates‐Bearing Sands and Their Sedimentology in the Nankai Trough
Authors: Uchida Takashi , Tsuji Takashi 
Published: November 2008

Abstract. The Nankai Trough parallels the Japanese Island, where extensive BSRs have been interpreted from seismic reflection records. High resolution seismic surveys and drilling site‐survey wells conducted by the MTI in 1997, 2001 and 2002 have revealed subsurface gas hydrate at a depth of about 290 mbsf (1235 mbsl) in the easternmost part of Nankai Trough. The MITI Nankai Trough wells were drilled in late 1999 and early 2000 to provide physical evidence for the existence of gas hydrate. During field operations, continuous LWD and wire‐line well log data were obtained and numerous gas hydrate‐bearing cores were recovered. Subsequence sedimentologic and geochemical analyses performed on the cores revealed important geologic controls on the formation and preservation of natural gas hydrate. This knowledge is crucial to predicting the location of other hydrate deposits and their eventual energy resource. Pore‐space gas hydrates reside in sandy sediments from 205 to 268 mbsf mostly filling intergranular porosity. Pore waters chloride anomalies, core temperature depression and core observations on visible gas hydrates confirm the presence of pore‐space hydrates within moderate to thick sand layers. Gas hydrate‐bearing sandy strata typically were 10 cm to a meter thick. Gas hydrate saturations are typically between 60 and 90 % throughout most of the hydrate‐dominant sand layers, which are estimated by well log analyses as well as pore water chloride anomalies.It is necessary for evaluating subfurface fluid dlow behavious to know both porosity and permeability of gas hydrate‐bearing sand to evaluate subsurface fluid flow behaviors. Sediment porosities and pore‐size distributions were obtained by mercury porosimetry, which indicate that porosities of gas hydrate‐bearing sandy strata are approximately 40 %. According to grain size distribution curves, gas hydrate is dominant in fine‐ to very fine‐grained sandy strata.
Detection of Methane Hydrate‐Bearing Zones from Seismic Data
Authors: Inamori Takao , Hato Masami 
Published: November 2008

Abstract. The MITI Nankai Trough wells were drilled offshore Japan in the Tokai area in 1999 and 2000. The occurrence of methane hydrate was confirmed by various indicators in the borehole logs and from core data. These findings have a large impact on potential future Japanese energy resources and other related‐scientific interests.We first tried to find the methane hydrate‐bearing zones using interval velocities derived from NMO velocity analysis. However, this analysis produced poor resolution. To achieve a more detailed delineation of the gas hydrate‐ and gas‐bearing zones, we executed a seismic impedance inversion calibrated by the logs from two of the MITI Nankai Trough wells. Although these two wells are only about 90 m apart, we were able to produce an impedance section with fine detail by adopting a simple initial model and incorporating physical properties of the methane hydrate‐bearing zones. The locations of the methane hydrate‐bearing zones are readily apparent in the final section.
Occurrence of Halogen‐rich Phlogopite in Late Cenozoic Volcanic Rocks in the Japanese Arcs
Authors: Imai Akira 
Published: November 2008

Abstract. Halogen‐rich phlogopite occurs in the groundmass of andesite and dacite lavas from Late Tertiary to Quaternary volcanoes associated with native sulfur and limonite deposits (Shiretoko‐Iwozan, Hachimantai, Adatara, Omeshidake, Masaki) and hydrothermal ore deposits (Harukayama, Muineyama, Hishikari) in Japan. The F contents of the halogen‐rich phlogopite range from 3.6 to 5.7 wt%, corresponding to atomic F/(F+C1+OH) ratios ranging from 0.45 to 0.69. On the other hand, the Cl contents of the halogen‐rich phlogopite are around 0.2 wt%. The atomic Mg/(Mg+Fe) ratios range from 0.69 to 0.83.The fluorine intercept value [IV(F)] defined by Munoz (1984) of the phlogopites ranges from 0.79 to 3.17, and the chlorine intercept value [IV(Cl)] ranges from ‐7.11 to ‐7.77. The observed IV(F) of the phlogopites broadly overlap the range of the IV(F) for biotites from porphyry copper deposits. On the other hand, the observed IV(Cl) are significantly lower than the IV(Cl) for biotites from porphyry copper deposits. Whereas the F contents of the phlogopite appear more prominent compared to the Cl contents, the calculation of halogen intercept values revealed that the phlogopites are enriched in Cl with respect to the element distribution effect of Mg‐Fe substitution. Since the degree of Cl enrichment of the phlogopite is more significant compared to that of biotite in porphyry copper deposits, the phlogopites are considered to have formed under the condition of significantly high activity of halogens. Hydrothermal ore deposits may be formed in magmatic hydrothermal system associated with volcanoes where halogen‐rich phlogopite is formed by hypersaline fluid.
Genesis of Kanggur Gold Deposit in Eastern Tianshan Orogenic Belt, NW China: Fluid Inclusion and Oxygen and Hydrogen Isotope Constraints
Authors: Wang Zhiliang , Jiang Neng , Wang Yitian , Mao Jingwen , Yang Jianmin 
Published: November 2008

Abstract. Primary fluid inclusions in quartz and carbonates from the Kanggur gold deposit are dominated by aqueous inclusions, with subsidiary CO2‐H2O inclusions that have a constant range in CO2 content (10–20 vol %). Microthermometric results indicate that total homogenization temperatures have a wide but similar range for both aqueous inclusions (120d̀ to 310d̀C) and CO2‐H2O inclusions (140d̀ to 340d̀C). Estimates of fluid salinity for CO2‐H2O inclusions are quite restricted (5.9∼10.3 equiv. wt% NaCl), whereas aqueous inclusions show much wider salinity ranging from 2.2 to 15.6 equivalent wt %NaCl.The 6D values of fluid inclusions in carbonates vary from ‐45 to ‐61 %, in well accord with the published δD values of fluid inclusions in quartz (‐46 to ‐66 %). Most of the δ18O and δD values of the ore‐forming fluids can be achieved by exchanged meteoric water after isotopic equilibration with wall rock by fluid/rock interaction at a low water/rock ratio. However, the exchanged meteoric water alone cannot explain the full range of δ18O and δD values, magmatic and/or meta‐morphic water should also be involved. The wide salinity in aqueous inclusions may also result from mixing of meteoric water and magmatic and/or metamorphic water.
Timing of the Mineralization and Volcanism at Cibaliung Gold Deposit, Western Java, Indonesia
Authors: Harijoko Agung , Sanematsu Kenzo , Duncan Robert A. , Prihatmoko Sukmandaru , Watanabe Koichiro 
Published: November 2008

Abstract. The Cibaliung deposit is a low‐sulfidation type epithermal gold deposit situated about 70 km west of the Bayah dome complex. The gold‐bearing quartz veins are hosted by basaltic andesite of the Honje Formation, which is comparable to the host rock of gold deposits at the Bayah dome complex.In order to clarify the timing of the mineralization and the volcanism at the Cibaliung area, two radiometric dating methods were applied. First, 40Ar/39Ar dating was conducted on six adularia samples to elucidate the age of mineralization. Second, K‐Ar method was applied to two samples of the host rock, andesite and the Cibaliung tuff, in order to reveal the timing of volcanism.The 40Ar/39Ar dating determined mineralization ages in the range from 11.18 to 10.65 Ma while the K‐Ar dating indicated the age of the andesite and the Cibaliung tuff to be 11.4±0.8 Ma and 4.9±0.6 Ma, respectively. These results imply that the epithermal gold mineralization in the Cibaliung area is related to the volcanic activity that produced the Honje Formation, while the Cibaliung tuff played an important role in the preservation of the Cibaliung deposit. The Cibaliung deposit is the oldest epithermal gold deposit yet discovered in western Java.
Exploration Indices and Mineral Potential Map of the Kuroko Deposits in Northeast Japan
Authors: Kubota Hiroshi , Urabe Tetsuro , Yamada Ryoichi , Tanimura Shojiro 
Published: November 2008

Abstract. Recent discoveries of seafloor hydrothermal mineralization in submarine volcanic centers of felsic magma in western Pacific island arcs are regarded as modern analogues of Kuroko type deposits. Studies of these deposits and their surrounding geology raised question whether the exploration activity for the Kuroko deposits on land which peaked in the 1960's was adequate or not. However, such an evaluation is not easy because the exploration data are about to be lost as a result of the closure of all the Kuroko mines in the area since 1994.The Metal Mining Agency of Japan (MMAJ), therefore, decided to compile existing data on about 180 Kuroko deposits and related mineral occurrences in northeast Japan as a new Kuroko database.This study extends a concept called “exploration indices” which was developed based on a case study of the thoroughly surveyed Hokuroku district to draw a potential map of the Kuroko occurrences for the entire northeast Japan quantitatively with a Geographical Information System (GIS). Effective exploration indices include: 1) distribution of dacitic‐rhy‐olitic submarine volcanic rocks of the Nishikurosawa and Onnagawa stages, 2) distribution of intrusive rocks of pre‐ and post‐Kuroko horizon, 3) low aeromagnetic anomaly caused by hydrothermal alteration of magnetite, 4) low gravity anomaly which suggests depressions in the basement rocks such as a tectonic basin and/or caldera, and 5) nearby existence of vein type deposits. It is concluded that about 33 % of known Kuroko deposits fall within the high potential zone (score=4 and 5) that occupies only 4 % of the entire northeast Japan arc. The Kuroko potential map is, therefore, useful for limiting the target area for Kuroko type deposits in an island arc setting.
A Possible Role of Boiling in Ore Deposition: A Numerical Approach
Authors: Hoshino Kenichi , Itami Tom , Shiokawa Ryouta , Watanabe Makoto 
Published: November 2008

Abstract. A possible role of boiling of the H2O‐NaCl‐CO2(‐H2S) fluid in ore deposition has been examined numerically by using the equations of state (EOS) of Duan et al. (1995, 1996), a modified EOS of Bowers and Helgeson (1983) and the water‐rock interaction simulator MIX99 (Hoshino et al., 2000).The following three models are examined to evaluate an efficiency of boiling on mineral precipitation: (1) hypothetical non‐boiling process, (2) hypothetical boiling process with sulfur partitioned only in liquid phases and (3) boiling process in which partition ratios of H2S between liquid and vapor phases are assumed to be the same as those of CO2. The processes are simulated from 450d̀C and 900 bar to 310d̀C and 620 bar with an analytical step of 10d̀C / 20 bar. Boiling occurs below 400d̀C in the latter two processes when the initial composition (in mole fraction) of the fluid is: XH2o = 0.84, XNaC1 = 0.10 and XCo2 = 0.06.Ore deposition occurs abruptly at a boiling point when the partition ratios of total sulfur (Xsvap/Xsliq) are as high as those of total carbon during boiling. A decrease of concentration of sulfur in the liquid phase during boiling leads to an increase of pH of the solution, resulting in propelling mineral precipitation. It has been made clear that a possible role of boiling in ore formation mainly depends on the partition ratios of sulfur between the liquid and vapor phases, although they cannot be estimated accurately by the currently available EOS.