Calc-silicates (garnet, epidote, clinopyroxene....) are common in skarns, but the skarn parageneses are also controlled by the composition of the country rocks around igneous intrusions, commonly granitic intrusions. Field studies are helpful to examine the extent of skarns in the aureole of intrusion. Comparison of the petrography of the metasomatized aureole with unaffected country rocks will help to know the type of parageneses developed as a consequence of contact metasomatism. Fe, Cu, and a range other metallic minerals (W, Au, Ag, etc.) have been reported in skarns, some in economically exploitable quantities.

Skarn deposits have variable mineralization styles, from Cu and base metals to Au, etc. Meinert et al., 2005 (SEG 100th Anniversary volume), has a very complete discussion of skarns, with some bits summarized below.

"Skarn deposits are one of the more abundant ore types in the earth's crust. Skarn is a relatively simple rock type defined by a mineralogy usually dominated by calc-silicate minerals such as garnet and pyroxene. Skarns are present on all continents and in rocks of almost all ages. Although the majority of skarns are found in lithologies containing at least some limestone, they can form in almost any rock type during regional or contact metamorphism and from a variety of metasomatic processes involving fluids of magmatic, metamorphic, meteoric, and/or marine origin. Although most are found adjacent to plutons, they also can occur along faults and major shear zones.

For the seven major skarn types (Fe, Au, Cu, Zn, W, Mo, and Sn) a general correlation exists between igneous major- and trace-element composition and skarn type. Plutons associated with Fe and Au skarns contain significantly more MgO and less K2O or SiO2, Au and Sn skarn plutons are more reduced, and Cu, Zn, and Mo skarn plutons are more oxidized than average. In terms of geochemical evolution, there is a fairly linear array from relatively primitive calcic Fe skarn plutons through Au, Cu, Zn, to W, Mo, to relatively evolved Sn skarn plutons. Calcic Fe skarn plutons are metaluminous, high in compatible elements such as Ni, V, and Sc, and have Rb/Sr

Quartz-bearing lime stones without dolomite are altered to marbles with wollastonite. If dolomite is added, marbles are formed with calcite, talc, tremolite, forsterite and diopside.

Marly limestones, that means carbonate with quartz and clay minerals, lead to marble with zoisite, grossular, anorthite, vesuvianite, and phlogopite. In many metasomatic contact aureoles, a systematic zoning of this mineralization is recognizable.

In various skarn types the following minerals can be formed: grossular/andradite-rich garnet, diopside/hedenbergite-pyroxene, wollastonite, various calcium-rich amphiboles, vesuvianite, epidote, ilvaite, magnetite, oxide ores, sulfide ores, fluorite, baryte, and scheelite. In dolomitic rocks, forsterite, phlogopite, spinel, and magnesite are common.

Skarn types that formed during sanidinite facies conditions produced rare minerals like monticellite, larnite, rankinite, merwinite, spurrite and tilleyite.

Best regards,

Guenter Grundmann

"A Dictionary of Geology & Earth Sciences" {Michael Allaby (ed), 2013. Oxford University Presss} defines skarn as "a contact metamorphic rock....composed of calcium, magnesium, and iron silicates (with or without iron, copper, and manganese sulphides and oxides) which has been derived from limestone or dolomite by the metasomatic....introduction of large amounts of silicon, aluminium, iron, and magnesium from a nearby igneous intrusion, usually a granite. Many skarns serve as host rocks for economic deposits of magnetite and copper sulphides".

However, other authors, as suggested by Jeffrey Hedenquist above, regard that skarns can be produced by contact as well as regional metamotphism. A nice summary is given in "Principles of Igneous and Metamorphic Petrology" by JD Winter (2010, Pearson Ed Inc.). An extensive review has also been given by Einaudi et al., 1981 (referred to by Winter).

Dear Mr. Mastoi,

please find as an example out of the great variety of skarn deposits those being mined for Fe.

H.G.Dill

The upload did not work. So I try again for Sn-W

H.G.Dill

To complete the skarn deposits (Au, Cu types have already been mentioned by colleagues)

H.G.Dill

Thanks all of colleagies Dr.Qasim,Mr. Jeffrey, Mr.Guenter, and H.G.Dill for such a nice responce and good shared paprs.

Hello

I invite you to read our article on high temperature skarns in Romania : The occurrence of high-temperature skarns from Oraviţa (Banat, Romania): A mineralogical overview.

Dear Essaid Bilal

Thank you very much for sharing your work.

Regards

Mastoi

Yes Dear Sir, Ioan Pintea, regarding this question i got very good and authentic anawers from varoius experts as Dr. Haralda ,Dr. Jan and many other expert researchers thanks to all seniors. Stay Blessed all.

Regards

Dr. Mastoi

Dear Mr. Mastoi Abdul Shakoor Mastoi

The paragenesis of Skarns is controlled by many parameters such as the chemical and mineralogical composition of the host rock, the composition of intrusion, the X-CO2 of fluids, the contribution of magmatic-metamorphic-meteoric fluids, the redox condition of metasomatism as well the pressure of metasomatism (which itself is controlled by the depth of emplacement and the permeability of wall-rocks). but overall we could presume Vesuvianite+Wollastonite paragenesis is being seen in Au-W and Cu deposits, while Turmaline+ - Dumortierite+ - other Boron minerals show correlation with Au and Sn deposits. Fe deposits often are related to Andradite garnet+Hedenbergite paragenesis.

Supergene pigment minerals can also be a sign. for example, Malachite+Azurite usually are present in Cu and Au skarn deposits.

but we should pay attention to the fact that skarn is a metasomatic rock, so we cant be so confident in order to respond to your question.

Kind regards

Ali

Dear , Ali Allahparast, regarding a question your answeris good, appriciated. Yes you are right we also found mineralization of malachite and azurite associated in these areas where we have marked the skern mineralization.

Thanks

Dr.Mastoi