ORE DEP (FELSIC PHANEROCRYSTALLINE) Flashcards
Deposits related to Felsic Phanerocrystalline Rocks
1) Pegmatitic
2) Granitic Tin
3) Granitic U
4) IOCG (Iron Oxide, Copper-Gold)
Generally dike like or lensoid which formed late in the crystallization associated with plutonic or Hypabyssal Rocks where volatiles cannot readily escape but in the deep seated high pressure environment
Pegmatites
Mineralogically simple, unzoned, formed when the more mobile qtzfldsphtc constituents of a rock are concentrated in dilation openings during met differenntiation and does not have economic value
Metamorphic Pegmatites
Products of Plutonic activity (Precambrian - Present )
Igneous Pegmatites
Type of pegmaites that is Uranium bearing but are not economical
Syenite Pegmatites
The only pergmatites associated with economic deposits
Granitic Pegmatites
a.k.a Unzoned Pegmatites
Homogenous Pegmatites
Zoned Pegmatites which are results of one period of crystallization after injection of water rich siliceous late stage melt
Heterogenous pegmatites
4 zones of heterogenous Pegmatite
1) Border Zone - outermost and have the Same mineralogy as wall zone but finer grained
2) Wall Zone - Plag, Perthite, Qtz and Muscovite subordinate tourmaline, apatite, Berly and garnet
3) Intermediate Zone - Up to 11 subzones can be present
4) Core Zone - Solid Mass of Barren Milky qtz w/ feldspars or qtz w/ large crystals of tourmaline or spodumene
IN what type of Granites is Uranium most abundant?
I-type granite, Alkali-rich Granites, S-type, pegmatites and related veins
Enrichment of U increases in
Silicecous Fractionated Late Melt
Morphology of Uranium
Disseminated and less veinlets
Main Ore
Uraninite
Other U-bearing Mienrals
traces in
Allanite
Titanite
Zircon
Monazite
Uranothorianite (U Th)(SiO4)2
Coffinite and
Brannerite
80% of the World’s Present Tin production came from this type which is a specialized, advanced differentiates of crustally derived granitoid melts due to partial melting of continental crust or sed rocks in orogenic belt
Tin Granites
Mainly the host granite which is cahracteriszed by two mica (Musco and Biot) more felsic that I-type, non porphyritic, shows internal variation, commlyn foliatied and assoc. w/ Met rocks and Orogenic Belt
S-Type Granite (Mas continental in origin)
Age of Granitic Tin
Phanerozoic
Example of Granitic Tin
Blue Tier, Tasmania
Deposits which are most productive Sn Deposts which are closely spaced nearly vertical greisen veinlets that extend to considerable deph
Floor
Highly altered granitic rock or pegmatite and is formed by self generating alteration of granite
Greisen
What type of skarn is Greisen?
Endoscarn
Deposits that are defined primarily by their elevated magnetite and/or hematite contents, constitute a broad, ill-defined clan related to a variety of tectono-magmatic settings.
Iron Oxide Copper Gold
Characteristic of IOCGs
1) No clear spatial associations w/ igneous intrusons but has a borad space-time assoc w/ Batholitic Granitoids and alkali Metasomatism
2) Has greater Fe oxides w/ Fe or Ti than most igneous rocks and bulk crust
3) Abundant Magnetite and Specularite (Crystalline Hematite)
4) Hydrothermal Ore style w/ strong structural controls
Example of IOCG
Olympic Dam, Australia
