bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geochemical Features of Vein Anhydrite from the Kakkonda Geothermal System, Northeast Japan
Authors: Sasaki Munetake , Fujimoto Koichiro , Tsukamoto Hitoshi , Sawaki Takayuki , Sasada Masakatsu , Kurosawa Masanori , Yagi Masahiko , Muramatsu Yoichi , Kato Osamu , Komatsu Ryo , Kasai Kaichiro , Doi Nobuo 
Published: November 2008

Abstract. Cathodoluminescence (CL) color, rare earth element (REE) content, sulfur and oxygen isotopes and fluid inclusions of anhydrite, which frequently filled in hydrothermal veins in the Kakkonda geothermal system, were investigated to elucidate the spatial, temporal and genetical evolution of fluids in the deep reservoir. The anhydrite samples studied are classified into four types based on CL colors and REE contents: type‐N (no color), type‐G (green color), type‐T (tan color) and type‐S (tan color with a high REE content). In the shallow reservoir, only type‐N anhydrite is observed. In the deep reservoir, type‐G anhydrite occurs in vertical veins whereas type‐T and ‐N in lateral veins. Type‐S anhydrite occurs in the heat‐source Kakkonda Granite. The CL textures revealed that type‐G anhydrite deposited earlier than type‐T in the deep reservoir, implying that fracture system was changed from predominantly vertical to lateral.Studies of fluid inclusions and δ34S and δ18O values of the samples indicate that type‐N anhydrite deposited from diluted fluids derived from meteoric water, whereas type‐G, ‐T and ‐S anhydrites deposited from magmatic brines derived from the Kakkonda Granite with the exception of some of type‐G with recrystallization texture and no primary fluid inclusion, which deposited from fossil seawater preserved in the sedimentary rocks. Type‐G, ‐T and ‐S anhydrites exhibit remarkably different chondrite‐normalized REE patterns with a positive Eu anomaly, with a convex shape (peak at Sm or Eu) and with a negative Eu anomaly, respectively. The difference in the patterns might result from the different extent of hydrothermal alteration of the reservoir rocks and contribution of the magmatic fluids.
Mineralogical and Genetical Aspects of the Doyashiki Kuroko Deposits, Hokuroku Basin, Japan
Authors: Kitazono Satoshi , Ueno Hirotomo 
Published: November 2008

Abstract. A detail investigation of ore and gangue minerals was performed on the Doyashiki Kuroko deposits, Hokuroku basin, Japan for the first time. Main ore minerals are sphalerite, galena, pyrite, chalcopyrite, tetrahedrite‐tennantite and digen‐ite. Small amounts of enargite, wittichenite, electrum, covellite, bornite, marcasite and hematite are also observed. Quartz, barite and gypsum are common gangue minerals. Homogenization temperatures and salinities of fluid inclusions in quartz, sphalerite and barite range from 190 to 240d̀C and 3.0 to 5.5 wt% NaCl equivalent, respectively. The FeS contents of sphalerite and Ag contents of electrum were 0.12 to 0.18 mol %, 39.0 to 39.6 atom %, respectively. The chemical composition of digenite as a primary mineral shows high sulfur contents.These data indicate that ore fluid responsible for digenite and associated ore minerals was characterized by a range of high sulfur fugacity with a moderate formation temperature. This is concordant with the mineral assemblage of bornite‐pyrite and chalcopyrite, which shows high sulfur fugacity conditions. It seems that the mineralization closely associated with acidic volcanism has occurred around 13 Ma of Middle Miocene on the seafloor at the depth of about 1500 m.
Mineralization Characteristics and Structural Controls of Hydrothermal Deposits in the Gyeongsang Basin, South Korea
Authors: Koh Sang‐Mo , Ryoo Chung‐Ryul , Song Min‐Sub 
Published: November 2008

Abstract. Hydrothermal deposits in the Gyeongsang Basin show the genetic relationship with igneous activity from Late Cretaceous to Early Tertiary in the spatial and temporal viewpoints. Many hydrothermal Au‐Ag‐Cu‐Pb‐Zn and clay deposits are dominantly distributed within the Gyeongsang Basin. The Gyeongsang Basin is divided into seven metallogenic provinces by spatial distribution. The age ranges of igneous activity and mineralization are 140∼40 Ma and 100∼40 Ma, respectively, and the most dominant age ranges of the both activities are from 90 Ma (Coniacian) to 50 Ma (Eocene). The age consistency between igneous activity and mineralization suggests that this age range is the climactic period of the hydrothermal activity of the Gyeongsang Basin. The metallogenic epochs in the Gyeongsang Basin are divided into three epochs of 100∼80 Ma (western part of the Gyeongsang Basin), 80∼60 Ma (central part of the Gyeongsang Basin), and 60∼40 Ma (eastern part of the Gyeongsang Basin). The mineralization and igneous activity tend to become young eastward in the Gyeongsang Basin.NNW‐SSE mineralized veins from 100 to 80 Ma in the western part of the Gyeongsang Basin are interpreted as the control of the parallel tensional fissures caused by NNW‐SSE compressional stress. NW‐SE mineralized veins from 80 to 60 Ma in the central part of the Gyeongsang Basin seem to have been formed under the same stress as that of the Gaeum and Yangsan Fault Systems. Namely, NW‐SE tensional stress is associated with a conjugate set of fracturing of the WNW‐ESE Gaeum Fault System and NNE‐SSW Yangsan Fault System. Also NE‐SW mineralized veins from 60 to 40 Ma in the eastern part of the Gyeongsang Basin seem to be controlled by the NE‐SW fractures. The fractures are related with NE‐SW compressional stress and are developed as secondary fractures within the dextral strike slip Yangsan Fault System.
Fluorite Deposits at Voznesenka in the Khanka Massif, Russia: Geology and Age of Mineralization
Authors: Sato Kohei , Suzuki Kazuhiro , Nedachi Munetomo , Terashima Shigeru , Ryazantseva Margarita D. , Vrublevsky Anatoly A. , Khanchuk Alexander I. 
Published: November 2008

Abstract. A huge fluorite deposit at Voznesenka in the Khanka massif, Far East Russia is concluded to have formed at ca. 450 Ma in Late Ordovician time based on the K‐Ar ages for Li‐micas in the fluorite ore and greisenized leucogranite within the deposit. This conclusion is inconsistent with the current view of Devonian mineralization that stemmed from widely scattered whole‐rock Rb‐Sr isotope data for the heterogeneous leucogranite stocks influenced by strong alteration. The Voznesenka and neighboring fluorite deposits may have formed in Cambrian limestone in relation to the intrusion of the Li‐F‐rich felsic magma which has a similar chemistry to representative Li‐F‐rich felsic rocks including topaz granite and ongonite or topaz rhyolite; these rocks may be classified as a specific group of highly fractionated felsic magmas.Biotite granite plutons exposed in the Voznesenka district are divided in age into two groups based on the CHIME age data for zircon, monazite and xenotime: Ordovician and Permian. The Ordovician plutons seem to be coeval to the fluorite deposits and are characterized by F‐rich chemistry, reduced nature and association of tin mineralization with the deposition of fluorite and tourmaline. The biotite granite magmas of initially enhanced F contents could have been highly fractionated to form Li‐F‐rich leucogranite cupolas that provided fluorite deposits within the host limestone. Future prospecting for similar fluorite deposits is to be focused on areas of intersection between Ordovician Li‐F‐rich granite and Cambrian carbonate sequences.The Permian granite of southeastern margin of the Grodekovo batholith is characterized by lesser F content, oxidized nature and the lack of tin and fluorite mineralization in contrast to the Ordovician granite. The result of Permian age does not support the current view of Silurian age for the batholith and requires overall chronological reinvestigation in connection with the tectonic history of the Khanka massif because the Grodekovo is a representative of Paleozoic batholiths in Primorie.
Preface
Authors: Matsumoto Ryo 
Published: November 2008

Editorial Board for the Special Issue on “Gas Hydrate in Nankai Trough, Japan”Takashi Uchida (JAPEX Research Center, Japan Petroleum Exploration Co., Ltd.), Amane Waseda (JAPEX Research Center, Japan Petroleum Exploration Co., Ltd.), Naotatsu Shikazono (Department of Applied Chemistry, Keio University), Yutaka Aoki (JGI Inc.) and Yoshihiro Tsuji (Technology Research Center, Japan Oil,Gas and Metals National Corporation)
BSRs and Associated Reflections as an Indicator of Gas Hydrate and Free Gas Accumulation: An Example of Accretionary Prism and Forearc Basin System along the Nankai Trough, off Central Japan
Authors: Baba Kei , Yamada Yasuhiro 
Published: November 2008

Abstract. Multi‐channel seismic data obtained from the Nankai accretionary prism and forearc basin system has been studied to elucidate the migration and accumulation process of gas to the BGHS and examine the distribution pattern of BSRs and characteristic reflections associated with them.BSRs are distributed widely in the Nankai accretionary prism and associated forearc basins (33,000 km2) and 90 % of them have migration and recycling origins. The widest distribution of the BSRs can be seen at the prism. A correlation between the BSR distributions and prism size shows that the BSRs tend to be more well‐developed in a prism of large size. This suggests that a large prism may produce much amount of gas‐bearing fluids that migrate to the BGHS and form the BSRs (tectonic control), hi the forearc basins, the BSRs are identified at topographic highs, anticlines and basin margins (structural control).The upward migration of gas‐bearing fluids is carried out through permeable sand layers and as a result, the distribution of BSRs is confined to alternating beds of sand and mud facies (sedimentary control). However, if there is enough time for upward migration and accumulation of gas to the BGHS, the BSRs can be generated widely in low‐permeable mud facies (time control).Those results imply that structural, tectonic, sedimentary and time controls are primary factors to decide the distribution of BSRs in the Nankai Trough area.
Occurrence of Free‐Gas Associated with Methane‐Hydrate‐Bearing Formations in the MITI Nankai Trough Wells, Offshore Tokai, Japan
Authors: Takayama Tokujiro , Nishi Masatoshi , Yamamoto Hiroaki , Sanada Yoshinori , Matsuda Shigemi , Uchida Takashi 
Published: November 2008

Abstract. The MITI Nankai Trough wells were drilled for exploration of methane‐hydrate‐bearing sediments in association with seismic inferred bottom simulating reflectors (BSRs). In this project, log data showed low velocity compressional‐wave (P‐wave) layers below methane‐hydrate‐bearing formations. Dipole shear sonic acoustic tools (DSI) could not acquire accurate compres‐sional velocity in this zone, thus it was not possible to accurately correlate between logging, VSP and surface seismic profiles.Small amount of gas was presumed to cause the problem in obtaining the low velocity P‐wave data. VSP interval velocity data was used to assess the DSI inferred low‐velocity layer, which showed lower values than the velocity of the drilling muds. Synthetic seismogram was created by VSP‐compensated velocity to compare against corridor stack of VSP. As a result, the depths above and below the methane‐hydrate‐bearing interval were correlated with synthetic seismograms and reflectivity events on the VSP profiles. By using this correlation technique, distribution of methane‐hydrate‐bearing formations and free‐gas‐bearing formations can be determined.
Application of AVO Analysis to Seismic Data for Detection of Gas below Methane Hydrate Stability Zone in Nankai Trough Area
Authors: Hato Masami , Inamori Takao , Bahar Alfian , Matsuoka Toshifumi 
Published: November 2008

Abstract. For the purpose of development of methane hydrate, occurring in the deep marine subsurface, as a resource, the most important issue is to understand the methane hydrate system (generation, migration and accumulation) as well as to delineate the methane hydrate reservoir properties. We have applied the Amplitude Versus Offset (AVO) analysis to the seismic data acquired in the Nankai Trough, offshore Japan, in order to confirm the occurrence of gas just below the methane hydrate‐bearing zone, assuming that gas will show a so‐called Class‐3 AVO response. Knowledge of the amount and occurrence of gas in the sediment below methane hydrate‐bearing zone is one of the keys to understand the methane hydrate system.We have utilized the qualitative analysis of AVO methodology to delineate how gas is located below the BSR, which is thought to be the reflection event from the interface between the methane hydrate‐bearing zone and the underlying gas‐bearing zone. In the region of MITI Nankai Trough Well PSW‐3, we observe two BSRs separated by 25 ms. After AVO modeling using well data, we applied AVO attribute analysis and attribute crossplot analysis to the seismic data. Finally we applied an offset‐amplitude analysis to CMP gather data at specific locations to confirm the results of AVO attribute analysis. The AVO analysis shows that there is very little gas located in the underlying sediment below methane hydrate‐bearing zone. This result supports the fact that we could not obtain any clear evidence of gas occurrence just below the methane hydrate‐bearing zone in the Nankai Trough well drilling.
High Resolution, Deep‐Tow Seismic Survey to Investigate the Methane Hydrate Stability Zone in the Nankai Trough
Authors: Ward Peter , Asakawa Eiichi , Shimizu Shoshiro 
Published: November 2008

Abstract. A high frequency deep‐tow seismic survey was carried out in the Nankai Trough area in 1996. The objective of the survey was to obtain high resolution seismic sections and velocity profiles of the methane hydrate zone, inferred from the strong BSR events seen on conventional seismic data in the area. A special feature of the survey is that both the source and the streamer cable are towed close to the seabed. This special acquisition geometry requires special data processing to handle the varying source and receiver depths. A CMP floating datum processing sequence was designed which led to high quality sections of the shallow geology. A key step in the processing was devising a residual statics technique to compensate for errors in the measured depths.The processing sequence was applied to a number of lines, totaling 200 km. The final data quality was highly variable. Some lines produced high quality sections and others, much poorer sections with few interpretable events. Conventional seismic data in the area also shows variation in the data quality so part of the reason is a variation in the sub‐sea geology, but the deep‐tow data is much more sensitive to change in conditions than conventional data. With the current acquired data and processing sequence the deep‐tow system offers most advantages when 1) the water depth is around 1 km or greater, 2) the seabed and underlying geology is not too complex, and 3) the acquisition proceeds smoothly with regular shotpoints, slowly varying depths, and with accurate positioning.
Application of a Simulation Model for the Formation of Methane Hydrate to the Nankai Trough and the Blake Ridge: Natural Examples of Two End‐member Cases
Authors: Baba Kei , Katoh Arata 
Published: November 2008

Abstract. Simulation experiments with a one‐dimensional static model for formation of methane hydrate are used to demonstrate models of hydrate occurrence and its generation mechanism for two end‐member cases. The simulation results compare well with experimental data for two natural examples (the Nankai Trough and the Blake Ridge).At the MITI Nankai Trough wells, the hydrate occurrence is characterized by strongly hydrated sediments developing just above the BGHS. Such occurrence can be reproduced well by simulation in which the end‐member case of upward advective fluid flow from below the BGHS is set. The strongly hydrated sediments is formed by oversaturated solution with free gas which directly enters the BGHS by the upward advective fluid flow. The recycling of dissociated methane of preexisting hydrate also contributes to the increase of hydrate saturation.At the Site 997 in the Blake Ridge area, the hydrate occurrence is characterized by thick zone with poorly hydrated sediments and no hydrate zone developing above the hydrate zone. Such occurrence can be reproduced well by simulation in which the end‐member case of in‐situ biogenic production of methane in the sediment of methane hydrate zone is set. The distribution pattern of hydrate saturation is basically controlled by that of TOC. However, the hydrate concentration near the bottom of the hydrate zone is increased by the effect of recycling of dissociated methane of pre‐existing hydrate. No hydrate zone expresses the geologic time needed until the local concentration of methane exceeds the solubility by gradual accumulation of in‐situ biogenic methane with burial.
Gold Deposits in Beishan Mountain, Northwestern China
Authors: Jiang Si‐Hong , Nie Feng‐Jun , Lie Yan 
Published: November 2008

Abstract. The Beishan Mountain spans three provinces ‐ Gansu, Xinjiang and Inner Mongolia, having an area of 120,000 km2 Tectonically, it transverses three different tectonic units, i.e. Siberia, Kazakhstan and Tarim plates, and is composed of nine ter‐rains with widely exposed Precambrian and Paleozoic strata, complex structures, intensive magmatic activities and widespread ore deposits. It is not only a main part of Tianshan‐Yinshan‐Great Hinggan metallogenic belt in China, but also a key to under‐stand the evolution of central‐Asian orogenic system.At present, more than 100 gold deposits and prospects have been discovered, explored and mined, among which Nanjinshan, Mazhuangshan, Liushashan, Jinwozi, Zhaobishan and Xiaoxigong are the most important ones. Based on the host rocks and the geological features, all these gold occurrences can be subdivided into three groups (or types): (1) hosted by Carboniferous or Permian volcanic or subvolcanic rocks; (2) hosted by or related to plutonic intrusions; and (3) hosted by Precambrian metamorphic rocks. The first group includes the Mazhuangshan gold deposit, which occurs in Hercynian quartz por‐phyry and rhyolite porphyry as gold‐bearing quartz veins. The second group is composed of the Liushashan, Nanjinshan Zhaobishan and Jinwozi gold deposits. Gold mineralization at these four deposits occurs within Hercynian granitoids intrusion: or late Paleozoic sedimentary rocks as quartz veins, veinlets and altered rocks. The Xiaoxigong gold deposit belongs to the third group, and is hosted by Precambrian schist, amphibolite and migmatite as quartz veins and altered rocks.Isotopic age dating data, geological and geochemical evidence suggest that most of the groups 1 and 2 gold deposits were generated during the emplacement of the Hercynian or partly Indosinian intrusions. These intrusions may provide both heat and metals for groups 1 and 2 deposits. In contrast, although the formation is closely related to the Hercynian magma‐tism, the ore‐forming materials of the group 3 deposits may not only come from the intrusions, but also from the Precambrian metamorphic rocks.
Magma Mingling/mixing vs. Magmatic Fractionation: Geneses of the Shirakawa Mo‐mineralized Granitoids, Central Japan
Authors: Ishihara Shunso , Tani Kenichiro 
Published: November 2008

Abstract. Leucocratic biotite granites are main components in the Hatogaya pluton and the Hirase stock in the Shirakawa region of central Japan. Molybdenite‐quartz vein mineralizations are widespread in and around the Hatogaya pluton and the Hirase stock, in which the largest is vein swarm of the Hirase mine. Mafic enclaves occur abundantly with granitic to granodi‐oritic matrix in the northern part of the Hatogaya pluton, while they are rare in the Hirase granitic stock. The enclaves with generally round shape have mostly diabasic to fine plutonic textures under the microscope, and show interfingering and lobate contacts with the felsic matrix. The enclaves are quartz monzodiorite in composition containing SiO>2 mostly around 60 %. They have felsic blebs, thus are considered a mingled magma of basaltic compositions originated in depth and a felsic magma generated from the Hida metamorphic‐plutonic complexes or their basement.The mingled magma further mixed with and reacted with the felsic magma with SiO2 70 %, and then formed granodiorite‐granite of the high Na group (Na2O higher than 4.25 %). Thus, compositional variation of the northern part of the Hatogaya pluton was caused by the magma mingling. The mingling happened to be deeper level produced homogeneous granodiorite of the Mihoro pluton. Biotite granite of the low Na group (less than 4.25 %) could have originated in a granitic magma generated also from the Hida metamorphic‐plutonic complexes or their basement. Most of the granites, occurring in the southern part of the Hatogaya pluton and Hirase stock, show high Rb/Sr ratio, strong Eu negative anomalies and flat REE patterns, and are thus considered as fractionated products of the SiO2 70 % original magma. The strong concentration of molybdenum in the Hirase stock can be explained by high degree of magmatic fractionation which produced MoS2‐rich residual melts, suitable fractures developed at the latest Cretaceous time, and preservation of the mineralized fractures at the present level of erosion.
Polymetallic Mineralization at the Suttsu Vein‐type Deposit, Southwestern Hokkaido, Japan
Authors: Ono Shuji , Hirai Koji , Matsueda Hiroharu , Kabashima Taro 
Published: November 2008

Abstract. The Suttsu polymetallic vein‐type deposit, hosted by tuff, tuff breccia and shale of the Miocene Kunnui Formation and propylitized hornblende‐augite andesite, is located in southwestern Hokkaido, Japan. It has been exploited and explored for Cu, Pb, Zn and Ag until 1962.In this study, we examined K‐Ar ages, ore mineralogical characteristics and fluid inclusions to obtain new data for the deposit.The K‐Ar ages on sericite indicate that the polymetallic mineralization occurred in Late Miocene (8.1–5.7 Ma). The polymetallic banded ore from the Ohkubo vein is characterized by an abundance of Au, Ag, Sn, Bi, in, Se and Te. These metals are mainly ascribed to electrum (30.3–37.8 atom% Ag), Se‐bearing pavonite (8.5–9.5 wt% Se), gustavite‐lillianite solid solution, Se‐bearing bismuthinite (5.0–5.3 wt% Se), kawazulite, cassiterite, Sn‐bearing chalcopyrite (3.3–4.2 wt% Sn), In‐bearing stannite, stannite‐chalcopyrite solid solution, and In‐ and Sn‐bearing sphalerite (2.6–8.4 wt% In and 1.8–4.3 wt% Sn), occurring in narrow bands of the ore. The In‐ and Sn‐bearing sphalerite likely forms a sphalerite‐roquesite‐stannite solid solution with the contents of roquesite and stannite being about 2–9 and 2‐A mole%, respectively. Temperatures and salinities (in wt% NaCl equiv.) of the ore fluids are estimated to be 180d̀‐250d̀C and 3–4 wt%, respectively. The Sn‐bearing chalcopyrite therefore probably precipitated metastably. The geologic and mineralogical features suggest that pre‐Tertiary basement rocks rich in organic material underlie the Miocene Kunnui Formation nearby the deposit and that they contributed to local and temporary reduction of magnetite‐series magmas favorable for the early stage tin‐polymetallic mineralization.