A scheelite mineralization in calc-silicate rocks of the Moldanubicum (Bohemian Massif) in Austria

Beran, A.; Göd, Richard; Götzinger, Michael; Zemann, J.

doi:10.1007/bf00204255

Cited by 10 publications

(2 citation statements)

References 17 publications

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“…Though considering this anaiytical handicap, the atomic moiar percentage of meionite in this mineral is very high (Me8388), as is usual in scapolite from W skarns and particu lariy from stratiform and/or strata-bound scheehte mineral izations (Beran et al, 1985;Pan, 1998).…”

Section: Piagiociasementioning

confidence: 99%

Mineralogy and Metasomatic Evolution of Distal Strata-Bound Scheelite Skarns in the Riba de Alva Mine, Northeastern Portugal

Gaspar¹

2000

Economic Geology

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The metasediment-hosted distal scheelite skarns from the Riba de Alva mine, Barca de Alva-Escalhão re gion, northeastern Portugal, consist of three main levels of strata-bound, boudin-shaped, 0.5-to 4-m-thick bod ies, having a total resource of 380,000 tons (t) with an average grade of 0.51 percent W03. The boudinage of the Cambrian metasedimentary rocks of the Siate Greywacke Complex occurred early during the Hercynian orogeny, prior to the Granitic Complex intrusion and the skarn-forming process. The Granitic Cornplex corre sponds to reduced, highly evolved, and metallogenically specialized S-type leucogranites, comparable to those commonly associated with Mo-poor W-F skarns.Four different skarn types were recognized: pyroxene skarn with Fe diopside ± anorthite; amphibole-epi dote skarns with actinolite + clinozoisite ± bytownite ± phlogopite; ore skarn with clinozoisite + scheelite + flu orite + calcite ± labradorite ± apatite ± Fe axinite ± armenite ± scapolite; and late-stage veins with quartz (or fluorite or calcite) ± clinozoisite ± andesine (or albite) ± adularia.Clinopyroxene ranges from Di80Hd29 to Di60Hd49. Amphibole compositions range from actinolite to Mg hornblende and are F rich (0.5-1.9 wt %). Clinozoisite, often zoned with Fe-poor cores, shows little composi tional variation in the skarn types, having a low pistacitic component (5-13% Ps). Plagioclase compositions grade from anorthite in pyroxene skarn through andesine and albite in late-stage veins. Phlogopite, as amphi bole, is F rich (2.45-4.70 wt %). Au extremely pure Mo-free scheelite, the only ore mineral present, is re stricted to the ore skarn type.The Riba de Alva skarns were formed, after intrusion of the Hercynian Granitic Complex, by selective infil trative metasomatic alteration of argillaceous dolomitic limestone. An early stage of prograde alteration led to the formation of the pyroxene skarn, through reaction with an Si-rich and Fe-bearing fluid. Scheelite mineral ization occurred during retrograde alteration, which was rnainly fracture controlled and is characterized by a pervasive infiltration metasomatism with minor diffusion in the skarn walls. This alteration started with hydra tion reactions to form amphibole-epidote skarns, probably under lower X~09 conditions. Ore skarn formation, with scheelite deposition, took place later during this retrograde stage, mainly along veins within the strata bound boudins, as the result of a decrease in temperature and/or significant changes in the activity of some fluid cornponents such as M/, F, Na, Mn, P, and B, and particularly an increase in aca. Monomineralic late-stage veins represent the waning stage of the skarn-forrning process.

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Section: Piagiociasementioning

confidence: 99%

Mineralogy and Metasomatic Evolution of Distal Strata-Bound Scheelite Skarns in the Riba de Alva Mine, Northeastern Portugal

Gaspar¹

2000

Economic Geology

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“…Tourmalinites associated with calc-silicate rocks of meta-evaporitic origin have been reported (Brown 1983;Behr et al 1983). Some mineralogically unusual calc-silicate rocks with stratabound scheelite mineralization in the Bohemian Massif, Austria, (Beran et al 1985) were interpreted as metaevaporites by H6gelsberger (1989). For the calc-silicate-hosted scheelite occurrences of the ACC the exhalative-hydrothermal model for tungsten transport and concentration is preferred, because: -scapolite, anhydrite or other minerals indicating former evaporites are lacking geochemical data did not reveal anomalous concentrations of elements which are typical for saline, evaporitic environments (Sr, Na etc.)…”

Section: Discussionmentioning

confidence: 97%

Stratabound tungsten mineralization in regional metamorphic calc-silicate rocks from the Austroalpine Crystalline Complex, Austria

Raith

1991

Mineral. Deposita

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Abstract. Stratabound tungsten mineralization in regional metamorphic calc-silicate rocks of probably Lower Paleozoic age is described from the polymetamorphic Austroalpine Crystalline Complex (ACC) of the Eastern Alps. Scheelite-bearing calc-silicate rocks which are often associated with marbles and tourmalinites are intercalated conformably with metaclastic rocks. Alkalipoor calc-silicate rocks with high amounts of clinozoisite/ zoisite, grossular, quartz, plagioclase, etc. are the most important host rocks for tungsten mineralization. These unusual calc-silicate rocks are products of regional metamorphism and are interpreted as reaction skarns. They have formed in the presence of a water-dominated fluid phase with very low Xco ~. In the Koralpe estimated P-T conditions are 650-700 ~ at 5 7 kb. The mineralogical composition and the mineral zoning of the calc-silicate rocks is controlled by the degree of the Hercynian and Eoalpine metamorphism. There are no signs of graniterelated skarn formation. Tungsten preconcentration is thought to be syngenetic/syndiagenetic. It is genetically linked to exhalative hydrothermal processes in other Lower Paleozoic terrains of the Eastern Alps.Scheelite is the common tungsten mineral in Ca-bearing lithologies. Before the importance of stratiform/ stratabound scheelite deposits was recognised, most carbonate-hosted and especially calc-silicate-hosted tungsten deposits were interpreted as skarns derived from

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Wolframite- and scheelite-bearing carbonate rocks of the Nock mountains, Austria: A new type of tungsten mineralization in the Eastern Alps

et al. 1989

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A scheelite mineralization in calc-silicate rocks of the Moldanubicum (Bohemian Massif) in Austria

Cited by 10 publications

References 17 publications

Mineralogy and Metasomatic Evolution of Distal Strata-Bound Scheelite Skarns in the Riba de Alva Mine, Northeastern Portugal

Mineralogy and Metasomatic Evolution of Distal Strata-Bound Scheelite Skarns in the Riba de Alva Mine, Northeastern Portugal

Stratabound tungsten mineralization in regional metamorphic calc-silicate rocks from the Austroalpine Crystalline Complex, Austria

Wolframite- and scheelite-bearing carbonate rocks of the Nock mountains, Austria: A new type of tungsten mineralization in the Eastern Alps

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