Aliabad marbles, Aliabad, Nagar District, Gilgit-Baltistan, Pakistani

Regional Level Types
Aliabad marbles	Mine Zone
Aliabad	Village
Nagar District	District
Gilgit-Baltistan	Territory
Pakistan	Country

Mining area profiting diverse marble levels up to 800 m above Aliabad village. Decent specimens of ruby, spinel and pargasite have been collected in the late 1980s when the deposit was discovered during Karakorum Highway construction.

Marketing of Nagar area ruby has a fierce competitor in Afghan Jegdalek material, of a similar if not better quality, in a more accessible location with rectilinear strata easier to mine and without the extreme steep that characterize Nagar marble outcrops.

Marble deposit notes:
A calcite-marble containing gem-quality ruby is exposed in the Hunza Valley, northwestern part of the Karakoram mountains, Pakistan zone of Kashmir. The marble forms concordant intercalations within sillimanite- and garnet-bearing biotite-plagioclase gneisses and mica schists. The metamorphic sequence is cut by discordant aplite and pegmatite dikes. The following mineral assemblages are recognized in the marble:
1) calcite + corundum + phlogopite ± margarite ± sheridanite ± Al-rich pargasite ± anorthite (An 96.7),
2) calcite + spinel ± corundum + phlogopite + sheridanite.
(Okrusch et al., 1976)

The petrography shows that ruby-bearing marbles formed in the amphibolite facies (T = 610 to 790 °C and P ~ 6 kbar). A fluid inclusion study defines the conditions of gem ruby formation during the retrograde metamorphic path (620 < T < 670 °C and 2.6 < P < 3.3 kbar).
The carbonates were enriched in Al and chromiferous-bearing detrital minerals, such as clay minerals that were deposited on the platform with the carbonates, and in organic matter. Ruby formed during the retrograde metamorphic path, mainly by destabilization of muscovite or spinel. The metamorphic fluid system was rich in CO₂ released from devolatilization of carbonates, and in fluorine, chlorine and boron released by molten salts (NaCl, KCl, CaSO₄). Evaporites are key to explaining the formation of these deposits. Molten salts mobilized in situ Al and metal transition elements contained in marbles, leading to crystallization of ruby.
(Garnier et al., 2008)

Other Regions, Features and Areas containing this locality

References