Geologic Structure and Environment of Metallic Mineralization in the Arabian Precambrian Shield, Saudi Arabia

Abstract

The Arabian shield of Saudi Arabia is mainly composed of granite, gneiss and volcanic rocks, age of which ranges from about 1000 to 500 m.y. These rocks are separated by two distinct tectonic lines, the Najd fault system and the Yemen fault system, that trend NW-SE direction and are 300 km apart (Fig. 1). Separated blocks are tentatively called, from north to south, the Northern block, the Central block and the Yemen block. Each of these large blocks consists of many various sized tectonic basins or blocks, which are controlled by NW-SE trending faults and subsidiary N-S or NE-SW trending faults.
Copper-zinc-lead mineralizations associated with mainly acidic volcanisms are found in the Halaban group or Jiddah formation. There are some indications that the volcanic rocks are formed under submarine condition. Sulfide minerals occur in the manner of massive, stratabound, network, vein and dissemination.
The mineralized area are located nearly at the boundary of individual blocks or intersections of tectonic elements. It seems likely that the submarine volcanisms took place along the boundaries between the uplifted and subsided blocks.
We have enough background for such tectono-volcanic environment in the Japanese green tuff region. The geologic structures in the Arabian shield are quite similar to those of the green tuff region, and environment of the mineralizations resembles that of Kuroko-type mineralization. The Precambrian base metal mineralization in the Arabian-African shield region may need some re-examinations with knowledge on geology in the green tuff region in Japan.