2017 Fiscal Year Research-status Report
Experimental modeling of diamond crystallization from C-O-H fluid under controlled oxygen fugacity
| Project/Area Number |
17K14417
|
|---|
| Research Institution | Ehime University |
|---|
Principal Investigator |
CHERTKOVA N 愛媛大学, 地球深部ダイナミクス研究センター, 特定研究員 (00791774)
|
|---|
| Project Period (FY) |
2017-04-01 – 2020-03-31
|
| Keywords | High pressure experiment / diamond anvil cell / external heating / in situ spectroscopy |
|---|
| Outline of Annual Research Achievements |
This work aims to model experimentally crystallization of diamond from the C-O-H fluid in equilibrium with eclogite using innovative in situ techniques. In FY 2017 a technical development of external heating system for the diamond anvil cell was carried out in order to perform in situ visual observations and spectroscopic measurements of the samples in the wide pressure and temperature ranges. Developed technique was successfully applied for Raman analysis of eclogite + C2H2O4 system in the temperature range exceeding 900 °C and in the pressure range to 6.5 GPa. Tungsten gaskets were used to maintain the oxygen fugacity close to the W-WO2 buffer equilibrium. At the highest experimental conditions a formation of polymeric carbon phases was observed along with the silicate minerals, which indicates that polymerization phenomenon suppresses crystallization of diamond in this chemical system.
|
| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
An external heating system was designed for the lever-type diamond anvil cell for spectroscopic analysis at simultaneous high temperatures and high pressures and it showed good performance in the experiments with silicate and C-O-H components. A manuscript, prepared based on research achievements and findings, was accepted for publication in the international journal.
|
| Strategy for Future Research Activity |
Using developed experimental technique, the types of fluids which are favorable for diamond formation will be studied in situ by Raman and infrared spectroscopy and then comparison of chemical trends obtained in the experiments with those observed in the inclusions in natural diamonds will be done. The fluid source for experiments will be changed from C2H2O4 to methane hydrate, which easily decomposes at elevated temperatures and has a composition closer to that of fluids in the subduction zones. The loading of methane hydrate into the sample chamber of diamond anvil cell requires low temperatures and is accompanied by technical difficulties, which are to be overcome in the future. For this reason, a carryover is conducted to FY 2018.
|
| Causes of Carryover |
When the entire diamond anvil cell is exposed to low temperatures, viscosity and resistance of bonding cement can change significantly. In this case, the risk of misalignment and breakage of diamond anvils increases. The carryover will be used to cover the cost of new diamond anvils.
|
