著者

寺島 進世意 鎌田 治郎 土屋 徹

出版者

The Society of Resource Geology

雑誌

鉱山地質 (ISSN:00265209)

巻号頁・発行日

vol.30, no.162, pp.211-227, 1980

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Metal Mining Agency of Japan (MMAJ) had carried out a systematic exploration program for regional mineral resources in the Bantan district, western Japan, using geologic, gravimetric, aeromagnetic and drilling methods, during a period of about seven years from 1971. The district embraces one of the major metallogenic provinces in this country, where famous polymetallic vein deposits of Ikuno and Akenobe are known.<BR>Although there are many exposures of magnetic body and high density body which are expected to cause magnetic and gravimetric anomalies in the district, the solutions derived from the conventional analysis of the data could not disclose the proper geologic boundaries because many anomalies of different wave-length and amplitude interfere each other to form composite anomalies.<BR>The authors reexamined the gravimetric data with the manual bandpass filtering process (TERASHIMA and TsucHIYA, 1976a, b; TERASHIMA and YOSHIZAWA, 1976; TERASHIMA et al., 1979) and clarified the subterranean geologic structure that is quite consistent with the surface geology. A remarkable conclusion of the new analysis is the existence of a relatively shallow, mostly hidden emplacement of granitic batholith in the central district, along the periphery of which major Sn- and W-bearing polymetallic mineralizations such as Akenobe-Ohmidani, Kawakami and Ikuno seem to occur.<BR>The aeromagnetic data were also reexamined with special attention to the distribution pattern of pair (positive and negative) anomalies of the second vertical derivatives and of pair (high and low) anomalies of the total magnetic field. The detailed magnetic structure thus obtained succeeded to delineate the distribution of granodioritic intrusives which have genetic relation to Mo-bearing mineralization in the district.