Geology and geochemistry of Jabal Ghadarah ophiolitic melange, Zalim Quadrangle, Central Saudi Arabia

الملخص EN

The Precambrian rocks encountered at Jabal Ghadarah area can be grouped into : metaultramafites, arc metavolcanosedimetary rocks, syn- to late-orogenic granitoids, intramontane molasse-type sediments and post-orogenic monzogranite.

At Jabal Ghadarah, the meta-ultramafic rocks and associated listvenites are mainly exposed along a NNE trending thrust fault dipping to the east, in contact with the arc metavolcanosedimentary rocks.

The metaultramafites are characterized by the presence of numerous fragments of variable sizes (metagabbros, metabasalts, schists, amphibolites and marble).

Major and trace elements distribution indicates that the metagabbros, metabasalts and amphibolites are tholeiitic in character and of ocean floor affiliation.

The amphibolites were derived either from mafic or ultramafic protoliths.

Chromite from the serpentinite and listvenite show a wide range of major oxides contents comparable to Alpine-type chromite.

The metaultramafites and associated rock fragments are interpreted as an ophiolitic mélange imbricated with the arc metavolcanosedimentary sequence during accretion of the Arabian shield, contrary to the intrusive nature suggested by earlier workers.