Approach to granitic rocks associated with ore deposits by means of field investigations and experiments between minerals and hydrothermal solutions.

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K05356
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 31020:Earth resource engineering, Energy sciences-related
• Research Institution: Waseda University
• Principal Investigator: Etsuo Uchida 早稲田大学, 理工学術院, 教授 (40185020)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 花崗岩 / 熱水性鉱床 / インドシナ / 鉱物 / 超臨界熱水溶液 / イオン交換平衡 / ジルコンU-Pb年代

Outline of Final Research Achievements

Various chemical analyzes and U-Pb dating were performed on granites in Cambodia, and southeastern and western Thailand. Judging from chemical signatures of the granites, southwestern Cambodia and southeastern Thailand are classified into the same geological province. The granites in the study area dated to 300-190 Ma and 120-55 Ma. The former thought to be associated with the collision of the Sibumas and Indochina terranes, and the latter associated with the subduction of the Paleo-Pacific plate.
In element partitioning experiments between mineral and hydrothermal solution, sphalerite and olivine were tested under supercritical conditions. Experimental results revealed that electronegativity dominates the element partitionong in sphalerite, and ionic radius in olivine.

Free Research Field

岩石・鉱物・鉱床学

Academic Significance and Societal Importance of the Research Achievements

Mae Ping断層の北東に位置するカンボジア北東部はLoei Fold Beltに属するが、Mea Ping断層の南西に位置するカンボジア南西部およびタイ南東部はSukhothai Zoneに属することが花崗岩類の化学的特徴から明らかになった。このことは、金属資源の探査において重要な指針となるものである。
鉱物と熱水間における元素分配に関しては、従来あまり多くの実験が行われてこなかったが、硫化物および珪酸塩鉱物を用いた実験から、その分配が硫化物では電気陰性度が支配しているが、珪酸塩鉱物ではイオン半径が支配していることが明らかになった。