Geochemical and Tectonic Evolution of Arc-Backarc Hydrothermal Systems, Volume 8

Preface. 1. Miocene-pliocene hydrothermal ore deposits in and around the Japanese islands. 1.1. General overview of metallogeny and tectonics in the Japanese Islands. 1.2. General overview and classification of hydrothermal ore deposits of Neogene age. 1.3. Kuroko deposits. 1.3.1. Geological characteristics. 1.3.2. Mineralogical characteristics. 1.3.3. Geochemical. 1.3.4. Depositional mechanism and origin of ore fluids. 1.4. Epithermal vein-type deposits. 1.4.1. Geological characteristics. 1.4.2. Mineralogical characteristics. 1.4.3. Geochemical characteristics. 1.4.4. Se- and Te-type Au-Ag deposits. 1.4.5. Depositional mechanism and origin of ore fluids. 1.4.6. Hishikari deposit: an example of Japanese epithermal Au-Ag vein-type deposits. 1.5. Evolution of tectonics and hydrothermal system associated with epithermal and Kuroko mineralizations. 1.5.1. Paleogeography and stress field. 1.5.2. Volcanic activity. 1.5.3. Tectonic influence on temporal and spatial relationships in Kuroko and vein-type deposits in southern Hokkaido, Japan. 1.5.4. Geochemical features of sedimentary rocks formed in the Japan Sea as a proxy for hydrothermal activity. 1.5.5. Mode of subduction and formation of back-arc basin. 1.6. Other hydrothermal ore deposits. 1.6.1. Polymetallic vein-type deposits. 1.6.2. Hg and Sb deposits. 1.6.3. Gold-quartz vein-type deposits (mesothermal-hypothermal vein-type deposits). 1.6.4. Hot spring-type gold deposits. 2. Present-day mineralization and geothermal systems in and around the Japanese islands. 2.1. Subaerial geothermal system and mineralization. 2.1.1. Chemical compositions of geothermal waters controlled by hydrothermal alteration mineral assemblage. 2.1.2. Na-K-Ca geothermometer. 2.1.3. Present-day mineralization in subaerial geothermal areas in Japan. 2.2. Comparison of active geothermal systems with epithermal vein-type deposits. 2.2.1. Distribution. 2.2.2. Metals. 2.2.3. Mineralogy. 2.2.4. Geochemical features of hydrothermal fluids. 2.2.5. Geological and tectonic environment and volcanism. 2.3. Submarine geothermal systems and associated mineralization. 2.3.1. Submarine metal precipitation at back-arc basins around the Japanese islands. 2.3.2. Characteristics of back-arc deposits in the Western Pacific. 2.3.4. Comparison of present-day back-arc deposits with Kuroko deposits. 2.3.5. Spatial relationship between back-arc deposits and epithermal gold deposits. 2.4. Comparison of back-arc deposits with midoceanic ridge deposits. 2.4.1. Hydrothermal solution. 2.4.2. Metal ratios and mineralogy. 2.4.3. Mechanism of formation of chimney and ore deposits. 2.4.4. Hydrothermal alteration. 2.5. Besshi-type deposits in comparison with Kuroko deposits and midoceanic ridge deposits. 2.5.1. General features and classification. 2.5.2. Geological characteristics. 2.5.3. Metamorphism and hydrothermal alteration. 2.5.4. Mineralogical characteristics. 2.5.5. Geochemical features. 3. Hydrothermal flux from back arc basin and island arc and global geochemical cycle. 3.1. Major element (alkali, alkali earth, silica) flux. 3.2. Volatile element (CO2, S, As) flux. 3.2.1. CO2 flux. 3.2.2. Causes for high CO2 concentration and origin of CO2 of hydrothermal solution from back-arc basins. 3.2.3. S flux. 3.2.4. As flux. 3.3. Other elemental flux. 3.3.1. Hg flux. 3.3.2. Mn flux. 3.3.3. Ba flux. 3.4. Comparison of back-arc hydrothermal flux with midoceanic ridge hydrothermal flux. 4. Influence of hydrothermal CO2 flux on tertiary climate change. 4.1. Tertiary climate change in relation to CO2 flux by volcanic, hydrothermal and metamorphic activities. 4.2. Computation on global long-term carbon cycle and climate change. 5. Summary. Subject Index.

Many Neogene hydrothermal ore deposits have been formed on and near the Japanese islands from the middle Miocene to the present day and today many subaerial and submarine active geothermal systems are active.

This book summarizes the geochemical and tectonic features, and the evolution of various types of ore deposits and current island arc and backarc hydrothermal systems in Japan starting with the Mesozoic.