Fluid Inclusion Studies of Hydrothermal and Metamorphic Processes.

1987 Fiscal Year Final Research Report Summary

• Project/Area Number: 61460056
• Research Category: Grant-in-Aid for General Scientific Research (B)
• Allocation Type: Single-year Grants
• Research Field: 鉱物学(含岩石・鉱床学)
• Research Institution: Hokkaido University
• Principal Investigator: YUI Shunzo Faculty of Science, Hokkaido University, 理学部, 教授 (10006637)
• Co-Investigator(Kenkyū-buntansha): TSUCHIYA Takamura Faculty of Science, Hokkaido University, 理学部, 教務職員 (80088848) ; SHIBA Masatoshi Faculty of Science, Hirosaki University, 理学部, 助手 (80125442) ; WATANABE Jun Faculty of Science, Hokkaido University, 理学部, 助手 (30000821)
• Project Period (FY): 1986 – 1987
• Keywords: Fluid Inclusion / Homogenization Temperature / Trimming Devise for Rock Thin Section / Nurukawa Kuroko Deposits / Tokoro Metamorphic Zone / 恐山噴気帯

Research Abstract

Fluid inclusions in quartz of hydrothermal origin and in metamorphic rock were investigated with the Linkam TH-600 RMS heating-cooling stage on the POH petrographic microscope. 1. A simple devise for trimming of doubly-polished thin section is designed.
2. Two types of gold mineralization are recently discovered at the Nurukawa Kuroko deposits, one is in beeded form just beneath the normal bedded Koroko, another is in stock-work rich in quartz at several tens of meter from the bedded one. In order to specify these two mineralization, homogenization temperatures of two phase inclution in quartz were measured but both are at round 270゜C without marked difference.
3. The Tokoro metamorphic rocks in the eastern Hokkaido were divided into five metamorphic zones, A through E. Pressure-temperature conditions of the four zones, B through E are estimated from mineral assemblages and experimental data on the minerals except zone A. Homogenization temperature in prehnite from the zone A are 85゜C-125゜C. Considered the correction for the assumed pressure, these values are in concordant with those estiomated to zone B. 4. Osorezan in Aomori-ken is well-known for the active hydrothermal action with heavy metal mineralization, for example, As, Sb, and T1. Recently, auriferous spring water and precipitates are discovered and active gold mineralization is estimated. Fragments of estimated vein quartz are observed near assumed explosion crater of small scale. Homogenization temperatures of fluid inculsions in the quartz show bimodal distribution. Largest concentration is at 210-22゜C, and second one at 250゜C. The former seems to be of secondary origin based on their shape and distribution, therefore, it is estimated that the second hydrothermal action is recorded in quartz grains primarily formed at round 250゜C.