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Arabian-Nubian Shield
The Arabian-Nubian Shield (ANS) is an exposure of Precambrian crystalline rocks on the flanks of the Red Sea. The crystalline rocks are mostly Neoproterozoic in age. Geographically - and from north to south - the ANS includes the nations of Israel, Jordan. Egypt, Saudi Arabia, Sudan, Eritrea, Ethiopia, Yemen, and Somalia. The ANS in the north is exposed as part of the Sahara Desert and Arabian Desert, and in the south in the Ethiopian Highlands, Asir province of Arabia and Yemen Highlands.
The ANS was the site of some of man's earliest geologic efforts, principally by the Egyptians to extract gold from the rocks of Egypt and NE Sudan. This was the most easily worked of all metals and does not tarnish. All of the gold deposits in Egypt and northern Sudan were found and exploited by Egyptians, but new gold discoveries have been found in Sudan, Eritrea, and Saudi Arabia. Pharonic Egyptians also quarried granite near Aswan and floated this down the Nile to be used as facing for the pyramids. The earliest preserved geologic map was made in 1150 BCE to show the location of gold deposits in Eastern Egypt; it is known as the Turin papyrus. The Greek name for Aswan, ''Syene''; is the type locality for the igneous rock syenite. The Romans followed this tradition and had many quarries especially in the northern part of the Eastern Desert of Egypt where porphyry and granite were mined and shaped for shipment. Precious and industrial metals, including gold, silver, copper, zinc, tin, and lead, have been mined in Saudi Arabia for at least 5,000 years. The most productive mine in Saudi Arabia, Mahd adh Dhahab ("Cradle of Gold"), has been periodically exploited for its mineral wealth for hundreds or even thousands of years and is reputed to be the original source of King Solomon's gold, although this may be more of a legend as there is no historical evidence that it ever occurred. Today, mining at Mahd adh Dhahab is conducted by the Saudi Arabian Mining Company, Ma'aden. Deposits of iron, tungsten, mineral sands, copper and phosphates have been found in many locations. Mining in the Eastern Desert of Egypt and Sudan is limited due to shortage of water and infrastructure. One option would be to bring water from the Nile by pipeline.
==Size==
The exposed Arabian Shield in Saudi Arabia encompasses ≈445,000 km2. The total Arabian Shield, including exposed parts plus what is hidden by younger lava flows and sediments, covers ≈725,000 km2. Exposed Shield rocks in Jordan and Yemen cover another ≈100,000 km sq. This equals ≈825,000 km2 for the Arabian side of the ANS. For the Nubian Shield, which is exposed in Egypt, Sudan, Eritrea, Ethiopia, S. Sudan, and Kenya: Exposed shield ≈801,000 km2; Subsurface shield ≈1,100,000 km2. This gives a total estimated area for the Nubian Shield ≈1,901,000 km2. The total area of exposed and inferred ANS ≈2,725,000 km2. This is slightly less than 30% of the area of the USA and 2% of Earth's continental area.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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