Re-Os geochronology of the kuroko and petroleum deposits and their metallogenic study

2014 Fiscal Year Final Research Report

• Project/Area Number: 24740360
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Petrology/Mineralogy/Science of ore deposit
• Research Institution: Japan Agency for Marine-Earth Science and Technology
• Principal Investigator: NOZAKI Tatsuo 独立行政法人海洋研究開発機構, 海底資源研究開発センター, 研究員 (10553068)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: Re-Os同位体 / 黒鉱鉱床 / 火山性塊状硫化物鉱床 / 泥岩 / 日本海 / 古海洋環境変動

Outline of Final Research Achievements

We conducted the Re-Os isotope geochronology on the kuroko VMS deposit in the Hokuroku area, Akita Prefecture. The Matsumine deposit which is the largest kuroko VMS deposit in Japan has been dated to be ca. 14.9 Ma. Initial Os isotope ratio of the Matsumine deposit is equivalent to that of concurrent seawater. The chemostratigraphic research for the mudstone collected from both pre- and post-kuroko mineralization layers revealed that relatively reducing condition was prevailed just after the main kuroko mineralization in the Japan Sea.
We have also performed the Re-Os isotope analyses of the Yurihara and Sarukawa petroleum deposits in the Akita Prefecture. The Re-Os isotope data of the crude oil samples do not exhibit the good linearity, but they are characterized by much lower Os-isotope compositions than those of source rocks (black shales), suggesting that mature of petroleum deposits in the green tuff belt was enhanced inorganically by hydrothermal fluid.

Free Research Field

地球化学，鉱床学