The Journal of the Japanese Association of Mineralogists,Petrologists and Economic Geologists最新文献

{"title":"Geology of Iwate volcanic group, northeastern Japan","authors":"M. Nakagawa","doi":"10.2465/GANKO1941.82.132","DOIUrl":"https://doi.org/10.2465/GANKO1941.82.132","url":null,"abstract":"Iwate volcanic group is situated at the southeastern portion of Hachimantai and surrounding volcanic clusters, northeastern Japan. It consists of several volcanic bodies extending in E-W direction, parallel to the maximum horizontal compressional axis of the tectonic stress in this region. The basement rocks of Iwate volcanic group are composed mainly of the Tertiary rocks and the early Quaternary rhyolitic welded tuff which is a member of the Tamagawa welded tuffs. The activity of Iwate volcanic group is summarized as follows. Matsukawa andesite : this andesite consists of altered lavas and pyroclastics and are exposed at the western portion of the volcanic group. Their K-Ar ages have been reported to be 1.62 and 1.36 Ma. Amihari volcanic group: it is divided into two substages, older and younger, according to preservation of their volcanic primary topography. Older stage: in early to middle Pleistocene, several volcanic bodies, composed of an alternation of lavas and pyroclastics, were built up at the nearly same time. They are arranged in E-W direction 12km in length. Younger stage: after the formation of the volcanic chain, two cinder cones and a lava dome were formed, and lava flows were effused from the western portion of the volcanic chain. It is possible that they were active during the growth of Iwate volcano. Iwate volcano: in middle or late Pleistocene, the activity of Iwate volcano started at the eastern portion of Amihari volcanic group. Its history consists of four substages, and involves collapse of the volcanic body. Older Iwate 1st stage: voluminous pyroclastics and subordinate amounts of lavas formed two stratovolcanoes, Kurokura and Older-Iwate volcanos, with a net height of about 2, 000m. Older Iwate 2nd stage: at about 0.15Ma, the southeastern portion of the Older-Iwate volcano collapsed to form Onimata caldera. After the collapse, lava flows and pyroclastics were erupted from the central and flank vents to fill the Onimata caldera. Older Iwate 3rd stage: west-Iwate caldera was formed at the top of Older-Iwate volcano. From the vent in the caldera, lavas and pumice were effused to built up a composite central cone, Onashiro cone. It seems that these activities started at about 0.05Ma and ceased before 0.03Ma. Younger Iwate stage: after more than 25, 000 years of pause, about 5, 000 years ago, East-Iwate caldera was formed at the eastern portion of Older-Iwate volcano. Pyroclastics and lava flows were eruped from the vents mainly within the caldera, resulting in the formation of the composite Younger-Iwate volcano, Yakushidake volcano (2, 040.5m). In 1719, Yakehashiri lava flow was extruded from the northeastern flank of the volcano. The eruptive rocks are mainly basalt and basaltic andesite and associated with andesite. Two types of mafic phenocryst assemblage in basaltic rocks, clinopyroxene+olivine and orthopyroxene+olivine, are found. Although quartz phenocryst often occur, no hornblende phenocryst is found in the rocks fr","PeriodicalId":22709,"journal":{"name":"The Journal of the Japanese Association of Mineralogists,Petrologists and Economic Geologists","volume":"291 1","pages":"132-150"},"PeriodicalIF":0.0,"publicationDate":"1987-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90799453","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Contrast behaviour of octahedral Cr3+ in clinopyroxenes at elevated pressure","authors":"H. Ohashi, T. Osawa","doi":"10.2465/GANKO1941.82.100","DOIUrl":"https://doi.org/10.2465/GANKO1941.82.100","url":null,"abstract":"","PeriodicalId":22709,"journal":{"name":"The Journal of the Japanese Association of Mineralogists,Petrologists and Economic Geologists","volume":"2 1","pages":"100-105"},"PeriodicalIF":0.0,"publicationDate":"1987-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74265791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Incompatible trace element abundances of basanite from Nanzaki volcano, Izu peninsula","authors":"K. Aoki, Takeyoshi Yoshida, K. Ishikawa","doi":"10.2465/GANKO1941.82.119","DOIUrl":"https://doi.org/10.2465/GANKO1941.82.119","url":null,"abstract":"","PeriodicalId":22709,"journal":{"name":"The Journal of the Japanese Association of Mineralogists,Petrologists and Economic Geologists","volume":"22 1","pages":"119-122"},"PeriodicalIF":0.0,"publicationDate":"1987-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82794810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Serpentine minerals from Sasaguri area, Fukuoka Prefecture, Japan","authors":"S. Uehara","doi":"10.2465/GANKO1941.82.106","DOIUrl":"https://doi.org/10.2465/GANKO1941.82.106","url":null,"abstract":"Serpentinized ultramafic rocks and Sangun metamorphic rocks occur in the Sasaguri area, Fukuoka Prefecture. Lizardite and antigorite are the most abundant rock-forming minerals in the Sasaguri ultramafic rocks and are accompanied by lesser amounts of chrysotile (2Mcl and 2Orcl), magnetite, chromite, pyrite, pentlandite, millerite, forsterite, chlorite, talc, tremolite, anthophyllite, calcite, dolomite, magnesite, aragonite, hydromagnesite, artinite, brucite, pyroaurite, coalingite, szaiberyite, sepiolite, and deweylite, Serpentinites can be divided into following four types by the assemblage and grain size of serpentine minerals: (1) lizardite serpentinite, (2) lizardite-antigorite serpentinite, (3) fine-grained antigorite serpentinite, (4) coarse-grained antigorite serpentinite. The representative rock-forming serpentine minerals (five antigorites and one lizardite) and the two vein-forming fibrous chrysotiles in lizardite serpentinite were examined by X-ray, chemical, electron optical, thermal, and infrared absorption analyses. The significant differences in chemical composition and structural properties of antigorties are found. Fine-grained antigorites have low Fe contents (total FeO=1.6-2.5 wt%) and long supercell parameters (A=41.8-42.5 A), and coarse-grained antigorites have high Fe contents (toal FeO=4.9-6.0 wt%) and short supercell parameters (A=35.4-40.5 A). Lizardite and chrysotile show low Fe contents (total FeO=1-3 wt%). Many lizardite serpentinites in this area contain chrysotile 2Mcl. Its proportion is approximately 20 to 30 wt%. Povlen-type chrysotile is found in the vein-forming chrysotile specimen by electron microscope examinations.","PeriodicalId":22709,"journal":{"name":"The Journal of the Japanese Association of Mineralogists,Petrologists and Economic Geologists","volume":"46 3 1","pages":"106-118"},"PeriodicalIF":0.0,"publicationDate":"1987-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83946679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Xenoliths of “olivine cumulates” from Ichinomegata and Sannomegata, Japan","authors":"S. Arai","doi":"10.2465/GANKO1941.82.51","DOIUrl":"https://doi.org/10.2465/GANKO1941.82.51","url":null,"abstract":"Xenoliths composed of megacrystalline pyroxenes and hornblende poikilitically enclosing various proportions of olivine are rarely found among mantle peridotites, websterites and mafic rocks in Ichinomegata and Sannomegata ejecta, northeastern Japan. These rocks from Sannomegata are distinct from those of Ichinomegata, which frequently have hornblende oikocryst. Olivine of the former is more magnesian (Fo88-85) than the latter (Fo85-8). Chromian spinel of the latter is distinctly higher in Fe3+/(Cr+Al+Fe3+) ratio than that of the former. Constituent mafic minerals are more Fe-enriched than those of the mantle peridotites and almost identical to those in websterites. Olivine cumulates may have been formed from magmas in equilibrium with Iherzolite residue, possibly after blending more fractionated websterite-forming magmas. The so-called cumulus mantle beneath Ichinomegata is poorer in olivine than that of southwestern Japan, which may be attributed to low content of olivine component in the initial melts that had formed the cumulus mantle beneath Ichinomegata.","PeriodicalId":22709,"journal":{"name":"The Journal of the Japanese Association of Mineralogists,Petrologists and Economic Geologists","volume":"10 1","pages":"51-59"},"PeriodicalIF":0.0,"publicationDate":"1987-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89431842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A kaersutite-bearing dunite xenolith from Ichinomegata, northeastern Japan","authors":"S. Arai, N. Takahashi","doi":"10.2465/GANKO1941.82.85","DOIUrl":"https://doi.org/10.2465/GANKO1941.82.85","url":null,"abstract":"A xenolith of dunite was found in the Ichinomegata ejecta, northeastern Japan. It consists of olivine (80%), clinopyroxene (7.4%), spinel-pyroxene symplectite (5.4%), chromian spinel (4.7%), plagioclase (1.3%), amphiboles (0.6%) and orthopyroxene (0.3%). Olivine is Fo86.8 in average composition, and Cr/(Cr+Al) atomic ratio of spinel is around 0.2. Al2O3 and TiO2 contents of clinopyroxene exceed 5 wt.% and 1 wt.%, respectively. Coexistence of relatively magnesian olivine with Al-rich spinel and Al- and Ti-rich clinopyroxene indicates a cumulative origin from some low-degree partial melt (e.g. alkali basalt) of a pyrolitic material. The dunite has suffered from metasomatic alteration which led to the subsolidus crystallization of titanian pargasite and kaersutite and the entrapment of fluid inculsions into olivine and spinel. Amphiboles in this rock are far more enriched in Ti than those in any ultramafic xenoliths ever documented from Ichinomegata. The metasomatizing fluid may have been enriched in Ti and Na over K, implying the consequence of some intra-plate magmatism.","PeriodicalId":22709,"journal":{"name":"The Journal of the Japanese Association of Mineralogists,Petrologists and Economic Geologists","volume":"28 1","pages":"85-89"},"PeriodicalIF":0.0,"publicationDate":"1987-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80455497","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structure of granitic rocks of the southern Ryoke belt, Kinki district, Japan","authors":"K. Masaoka","doi":"10.2465/GANKO1941.82.60","DOIUrl":"https://doi.org/10.2465/GANKO1941.82.60","url":null,"abstract":"Structure of granitic rocks (Cretaceous in age) distributed in the southern part of the Ryoke belt in the Kinki district has been studied. The granitic rocks intruded through three stages. The first stage granites (gneissose tonalite to granodiorite) distributed in the northern part of the studied area have undergone both D1 and D2 deformation. The D1 deformation is characterized by overspread foliation (S1) trending at low to moderate angles to the general trend of the Ryoke belt. The D2 deformation is of the left-lateral sense and resulted in the formation of strongly mylonitized belt of several kilometers wide along the Median Tectonic Line. Upright folds of left-hand echelon are also associated with the D2 deformation. The second stage granites (massive or schistose granite to granodiorite) distributed in the southern part of the studied area have undergone minor and local de formation (D3) characterized by branching shear belts caused by shear stress of left-lateral sense. The third stage granites (massive to weakly schistose tonalite to granodiorite), occurring as a pluton between the first stage and second stage granites, have undergone minor and local deformation (D4) caused by shear stress of left-lateral sense.","PeriodicalId":22709,"journal":{"name":"The Journal of the Japanese Association of Mineralogists,Petrologists and Economic Geologists","volume":"73 1","pages":"60-74"},"PeriodicalIF":0.0,"publicationDate":"1987-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80576655","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ultramafic rock in the hornblende porphyrite dike of the Tamba Belt, Southwest Japan","authors":"Michio Kiji","doi":"10.2465/GANKO1941.82.75","DOIUrl":"https://doi.org/10.2465/GANKO1941.82.75","url":null,"abstract":"Ultramafic rock is found associated with the hornblende porphyrite dike (intermediate rockwith SiO2 53.39% and MgO 9.09%) which has intruded shale of late Jurassic age in Tamba Belt.It is mainly composed of euhedral to subhedral Mg-rich olivine and anhedral to subhedral brown Ca- amphibole with subordinate amounts of clinopyroxene, phlogopite, chromite, and etc.According to the classification after IUGS (1973), the modal composition indicates hornblendeperidotite class. Olivine is mostly replaced by serpentine, brucite, opaque iron oxide. Brown Ca- amphiboles have pargasitic compositions. Clinopyroxenes are diopsidic and are rich in Cr. According to the textural features, this rock can be called olivine-clinopyroxene orthocumulatepossessing well-developed interstitial amphiboles. Field and petrol ogical studies suggest that theultramafic rock has cognate relation to the hornblende porphyrite and was formed under thewater-rich condition.","PeriodicalId":22709,"journal":{"name":"The Journal of the Japanese Association of Mineralogists,Petrologists and Economic Geologists","volume":"10 1","pages":"75-80"},"PeriodicalIF":0.0,"publicationDate":"1987-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78713497","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Strontium isotope ratios of the products from the Adachi volcano, Northeast Japan","authors":"S. Kanisawa, K. Shibata","doi":"10.2465/GANKO1941.82.81","DOIUrl":"https://doi.org/10.2465/GANKO1941.82.81","url":null,"abstract":"The Adachi volcano situated to the west of Sendai, Northeast Japan is assumed to be thesource of the Adachi-Medeshima pumice belonging to the Late Pleistocene. Strontium isotoperatios of four samples of the products of the Adachi volcano were determined. The determinedrocks are 1) fresh and white pumice (cummingtonite dacite), 2) cummingtonite dacite (lithicfragment), 3) leucocratic cummingtonite tonalite (lithic fragment), 4) hornblende bearing cummingtonite tonalite (lithic fragment). 87Sr/86Sr ratios of all the rocks fall within a narrow rangebetween 0.70435 and 0.70447. The results obtained in the present study support an assumption thatthese rocks are co-genetic in origin.","PeriodicalId":22709,"journal":{"name":"The Journal of the Japanese Association of Mineralogists,Petrologists and Economic Geologists","volume":"31 1","pages":"81-84"},"PeriodicalIF":0.0,"publicationDate":"1987-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74759303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mesozoic granitic rocks of South Korea: Trace element evidence regarding their differentiation","authors":"A. Tsusue, T. Mizuta, T. Tamai, Sangwook Kim","doi":"10.2465/GANKO1941.82.23","DOIUrl":"https://doi.org/10.2465/GANKO1941.82.23","url":null,"abstract":"To understand the mode of differentiation of the Jurassic and Cretaceous granitic magmas in South Korea, a neutron activation analysis has been made to measure the REE abundance of the granitic rocks. We used the Rayleigh fractionation model as a crystallization model of the granitic melts. Since the model calculations fit the REE data for the Cretaceous granitic rocks very well, it is suggested that the Cretaceous granitic magma in South Korea were mainly differentiated by fractional crystallization. Because the REE patterns for the Jurassic granitic rocks do not show large negative Eu anomalies, it is difficult to consider that the Jurassic granitic magmas were chiefly differentiated by fractional crystallization.","PeriodicalId":22709,"journal":{"name":"The Journal of the Japanese Association of Mineralogists,Petrologists and Economic Geologists","volume":"24 1","pages":"23-35"},"PeriodicalIF":0.0,"publicationDate":"1987-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84252602","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}