| Author(s) | Jomaah A. AI-Alawi |
| Affiliation | Department of Geology. College of Science. King Saud University. Riyadh. Saudi Arabia |
| Title | Geochemistry and Chromium Enrichment of the Hamumah |
| Source | Journal of King Saud University. Science. Volume 11, No 2. (1999/1419) |
| Abstract | Jabal Hamumah is a small, isolated, intrusive plug located in the Khamis Mushayt quadrangle, southern Saudi Arabia. The pluton is composed of shonkinite (mafic syenite) intruding the Khamis Mushayt Gneiss which is the oldest known lithostratigraphic unit in the basement complex of the Saudi Arabian Shield. In the upper zone the shonkinite is composed of olivine, pyroxene (Orthopyroxene), plagioc1ase, perthite, and biotite, but in the lower zone the mineralogy changes drastically to produce a rock rich in hydrous minerals such as amphiboles (anthophyllite and tremolite-actinolite) and chlorite. Geochemical analysis shows that Mg, Cr, and Ni were highly enriched in the lower zone, while the other major and trace elements have been greatly depleted. Post-magmatic alteration due to the action of meteoric or hydrothermal water on the shonkinite has produced a different rock in which leaching of Ti, AI, Na, and other trace elements has resulted in a high concentration of Mg, Cr, and Ni in the lower zone. |
