Petrography and geochemistry of the dariyah granite, central Arabian Shield

Abstract EN

The Dariyah granite, quarried for the use as a facade for the Holy Mosques in Makkah 'ind Al-Madinah.

belongs to the late-stage plutonics of the Arabian Shield (585 ± 8 Ma).

It is a typical Icucocratic equigranular coarse-grained 'trans-solvus' granite formed dominantly of perthite.

both orthoclase and microeline, quartz and oligoclase.

Plagioclase crystallized first followed by potash feldspar then quartz.

The granite is slightly peraluminous with low Ca.

Mg.

Fc and Ti contents.

Its Ab-Qz-Or composition indicates a near minimum melt polassic granite.

Compared to average abundance of granites, it is significantly depleted in the incompatible elements Ba, Sr.

Zr, Cc, La, Y.

and Nd.

Thromon-Tuttle indices as well as Rb/Sr and K/Rb ratios suggest fairly evolved stage of differentiation.

The initial K7Sr/">Sr ratio (0.7037 ± 0.0003) suggests derivation from mantle source with limited crustal contamination or by low' degree partial melting of the lower crust.

Petrochemical and geochemical features however, support a crustal melt origin.