2003 Fiscal Year Final Research Report Summary
An integrated genefical model and exploration/evaluation system for chromittite and platinum-group element ores
| Project/Area Number |
13554017
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 展開研究 |
|---|
| Research Field |
Petrology/Mineralogy/Science of ore deposit
|
|---|
| Research Institution | KANAZAWA UNIVERSITY |
|---|
Principal Investigator |
ARAI Shoji Kanazawa University, Faculty of Science, Professor, 理学部, 教授 (20107684)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
MATSUMOTO Ichiro Shimane Univ., Fac.Education, Assistant Professor, 教育学部, 助教授 (30335541)
|
|---|
| Project Period (FY) |
2001 – 2003
|
| Keywords | chromitite / podifrom chromitite / stratiform chromitite / magma mixing / basaltic magma / silicic melt / Oman ophiolite / mantle / crust |
|---|
| Research Abstract |
An integrated model for chromitite genesis has been established through the petrological research of upper crustal podifarm chromitite that we found from the Oman ophiolite. Ihis chromitite is lenficular and was formed at the boundary between the late-intrusive peridotite and felsic partial meltfrom gabbroic blocks captured by the late intrusion. Despite the podiform character, its spinel is perfectly euhedral and fine and has a matrix of plagioclase. Spinel is rich in Cr and total Fe. These features are similar to those of the stratiform chromitite. In short, this chromitite has an intermediate character between the podiform and stratiform chromitites. It was formed by mixing of two kinds of magma, a basaltic one from the late intrusive body and a felsic one from the partial melt of gabbro. The chemical similarity between the upper crustal chromitite from Oman and the stratifrom chromitite may mean that the latter is also formed by mixing of magmas, a basaltic magma and a silicic one formed by partial melting of wall of the magma reservoir as first suggested by Irvine(1975). Combined with an interpretation of Arai and Yurimoto(1994) on the origin of podiform chromitite in peridotite, the mixing of two kinds of magma, basaltic and silicic ones, is indispensable to genesis of chromitite irrespective of type. This mechanism favors the precipitation of primary PGM by supplies of PGE from basalt and of S from a silicic melt.
|
