Phlogopites and potassic richterites from mica nodules in South African kimberlites     

Ken-ichiro Aoki 《Contributions to Mineralogy and Petrology》1974,48(1):1-7

Mica nodules from the Dutoitspan and Wesselton mines, Kimberley can be divided into two groups: diopside-phlogopite nodules and potassic richterite-phlogopite nodules. The latter is characterized by the presence of abundant potassic richterite (less than 50% by volume) and large size of the crystals (up to 1 cm in length). It seems this type nodule is the first finding. Phlogopites and potassic richterites show a rather wide variations of major elements they have low Al₂O₃ and high Fe₂O₃, with Fe⁺³ in addition to Al⁺³ in the tetrahedral sites. It is believed that the mica nodules would be produced from kimberlitic and related magmas under moderate temperature and pressure conditions.  相似文献   

Classification of the Sibumasu and Paleo-Tethys tectonic division in Thailand using chert lithofacies     

Yoshihito  Kamata  Katsumi  Ueno  Hidetoshi  Hara  Megumi  Ichise  Thasinee  Charoentitirat  Punya  Charusiri  Apsorn  Sardsud  Ken-ichiro  Hisada 《Island Arc》2009,18(1):21-31

Two types of chert are defined in Thailand based on lithology, faunal content, and stratigraphy. 'Pelagic chert' consists of densely packed radiolarian tests in a microcrystalline quartz matrix with no terrigenous material and is found as blocks embedded within sheared matrix. 'Hemipelagic chert' also has a microcrystalline quartz matrix, and contains not only scattered radiolarian tests, but also calcareous organisms such as foraminifers. The pelagic cherts range in age from Devonian to Middle Triassic, whereas hemipelagic chert is only from the Early to the Late Triassic. Lithological and stratigraphic characteristics indicate that the pelagic chert originated in the Paleo-Tethys, whereas the hemipelagic chert accumulated on the eastern margin of the Sibumasu Block. The hemipelagic and pelagic chert are exposed in two north-trending belt-like zones. The western zone includes the hemipelagic chert, as well as glaciomarine and other Paleozoic to Mesozoic successions, overlying a Precambrian basement that consists exclusively of Sibumasu elements. The eastern zone contains pelagic chert and limestone and should be correlated to the Inthanon Zone. The Inthanon Zone is characterized by the presence not only of Paleo-Tethyan sedimentary rocks, but also of Sibumasu Block elements that structurally underlie the Paleo-Tethyan rocks. The boundary between the Sibumasu and Paleo-Tethys zones is a north-trending, low-angle thrust that resulted from the collision of the Sibumasu and Indochina blocks.  相似文献   

Synthetic Fluid Inclusions in the Systems NaCl-H₂O and NaCl-CO₂-H₂O: Dissolution Temperatures of Halite     

Hiroki Nagaseki  Ken-ichiro Hayashi 《Resource Geology》2006,56(2):133-140

Abstract. This study examined the effect of CO₂ on NaCl solubility in hydrothermal fluid, with the synthetic fluid inclusion technique. Fluid inclusions of 30–40 wt% NaCl and 5 mol % CO₂ were synthesized, and their halite dissolution temperatures, T_m(halite), were measured. The solubilities of NaCl in CO₂-bearing aqueous fluid were obtained at 160–320C under vapor-saturated pressures. The T_m(halite) value in aqueous fluid with 5 mol % CO₂ obtained in this study agrees with that of Schmidt et al. (1995), showing that 5 mol % CO₂ reduces the solubility of NaCl by about 1 wt%.
Calculation of magnetite solubility suggests that 5–10 mol % CO2 decreases magnetite solubility by 4.5–8.9 % relative to the magnetite solubility in CO2-free solution. Therefore, an increase of CO2 content in ore-forming solutions may cause deposition of iron minerals and produce ore deposits.  相似文献   

Permo–Triassic granitoids of the Xing’an–Mongolia segment of the Central Asian Orogenic Belt,Northeast China: age,composition, and tectonic implications     

Qiu-Ming Pei  Shou-Ting Zhang  Ken-ichiro Hayashi  Dong Li  Li Tang 《International Geology Review》2018,60(9):1172-1194

The Xing’an–Mongolia orogenic belt is located in the southeastern segment of the Central Asian Orogenic Belt. Its tectonic evolution, especially during the Late Palaeozoic to Early Mesozoic, remains controversial. Here, we report new zircon U–Pb dates, whole-rock geochemistry, and Hf isotopes of representative samples from four plutons in the Linxi area of Northeast China to provide new constraints on this issue. Zircon U–Pb dating indicates that the intrusions were emplaced in two stages: (1) Late Permian to Early Triassic (the Banshifangzi and Xinangou plutons (252 ± 3)–(246.3 ± 3.3) Ma); and (2) Late Triassic (the Baoshan and Hada plutons (220.8 ± 2.7)–(211.4 ± 2.6) Ma). Their positive εHf(t) values (6.6–14.1), coupled with their geochemical characteristics, suggest that the provenance of investigated granitoids were most likely to be dominated by juvenile crustal materials. Based on these new data and previous studies, we propose three stages of tectonic evolution during the Late Palaeozoic–Early Mesozoic in the XMOB: (1) Late Carboniferous–Early Permian (330–270 Ma): double-sided subduction of the Palaeo-Asian Ocean; (2) Middle Permian–Middle Triassic (270–237 Ma): the closure of the Palaeo-Asian Ocean and subsequent continent–continent collision between the North China Craton and the South Mongolia Terrane; and (3) Late Triassic (237–211 Ma): post-collisional extension.  相似文献   

伊朗南部高扎格罗斯浊积放射虫岩亚带的放射虫地层学(英文)     

Ken-ichiro HISADA  Yoshihito KAMATA 《地球学报》2012,(Z1):18-20

Zagros orogen extends from the Turkish-Iranian border to NW,to the Makran area in SE.According to Geological Survey of Iran 100,000 series "Sureyan", "Saadatshahr","Abadeh-E-Tashk" and "Arsenjan",the Zagros orogen comprises the following sub-parallel tectonostratigraphic domains,from SW to NE:the  相似文献