Summary
Potassium-fluor-richterite is reported from wollastonite-rimmed metachert bands embedded in marbles of the Bufa del Diente aureole, NE-Mexico. K-F-richterites were generated via reaction of previously formed contact-metamorphic diopside with infiltrated hypersaline brines of magmatic origin that used the metachert bands as metamorphic aquifers. Their formation occurred at peak metamorphic conditions of 500 to 600 °C at 1 kbar according to the generalised reaction 10 CaMgSi2O6 + 8 SiO2 + 2 KClaq + 6 NaClaaq + 4 H2O + 4 HF diopside + quartz = 2 KNaCaMg5Si8O22(F)2 + 4 Ca2NaH(SiO3)3 + 8 HClaq K-F-richterite + pectolite Compositional ranges in two samples are K-Ri58−69Ri16−25Tri12−21 and K-Ri58−66Ri32−40Tr0−5. Mg/(Mg + Fe2+) ranges from 0.81 to 0.95, F/(F + OH) from 0.55 to 0.85, and the K-F-richterites are Cl-free.
Microthermometrically determined K/(K + Na)-ratios of hypersaline brines trapped at 500°C to 600°C range from 0.50 to 0.64, resulting in distribution coefficients K Amph-F1DK-Na = X AmphK(in A) /X AmphN(in A) · X F1Na /X F1K of 0.85 to 1.3 for the Na-K amphibole-fluid exchange reaction. Very low Ca-contents in bulk fluid leachates indicate that Cacontaining fluids cannot coexist with richterite and that Ca is incorporated into amphibole as a tremolite component. Amphibole compositions in Al-free systems can predict Na-K-Ca-ratios of metasomatic brines that equilibrated with them. Despite the hypersaline nature of the brines, Cl is not incorporated into the Mg-rich K-F-richterites because of the Mg-Cl and Fe-F avoidance rules in amphiboles.
Zusammenfassung
In die Marmore der Kontaktaureole des Bufa del Diente-Alkalisyenits sind 5-15 cm mächtige Quarzitbänder eingeschaltet, die mehrere cm-dicke Wollastonitsäume aufweisen. Die Metaquarzite enthalten Kalium- und Fluor-reiche Richterite. Die K-FRichterite bildeten sich durch Reaktion von zuvor gebildetem, kontaktmetamorphem Diopsid mit infiltrierenden hochsalinaren Fluiden magmatischen Ursprungs. Die Metaquarzite dienten als metamorphe Aquifere für diese Fluide.
Die K-F-Richterite wurden bei den Maximaltemperaturen der Kontaktmetamorphose von 500-600°C bei 1 kbar nach der folgenden schematischen Reaktion gebildet: 10 CaM9Si2O6 + 8 SiO2 + 2 KClaq + 6 NaClaq + 4 H2O + 4 HF Diopsid + Quarz = 2 KNaCaMg5Si8O22(F)2 + 4 Ca2NaH(SiO3)3 + 8 HClaq K-F-Richterit + Pektolit Der Zusammensetzungsbereich von zwei Proben aus unterschiedlichen Metaquarzitbändern liegt bei K-Ri58–69Ri16–25Tr12–21 und K-Ri58–66Ri32–40Tr0–5. K-FRichterite in beiden Proben haben F/(F + OH)-Verhältnisse von 0.55 bis 0.85 und enthalten kein Cl.
Mikrothermometrisch bestimmte K/(K + Na)-Verhältnisse der bei 500°-600°C in Flüssigkeitseinschlüssen okkludierten, hochsalinaren Fluide betragen 0.50–0.64. Daraus lassen sich Verteilungskoeffizienten K Amph-FiDK-Na = X AmphK(in A) /X AmphN(in A) · X F1Na /X F1K von 0.85-1.3 für die Amphibol-Fluid Austauschreaktion in tremolitfreien Amphibolen ableiten. Wässrige Extrakte der Gesamtfluidpopulationen enthalten sehr geringe Ca-Konzentrationen im Vergleich zu K und Na. Dies zeigt, daß Fluide mit signifikanten Ca-Konzentrationen nicht mit Richteriten koexistieren können und Ca bevorzugt als Tremolitkomponente eingebaut wird. Amphibolzusammensetzungen in Al-freien Systemen eignen sich als Indikatoren für K-Na-Ca-Verhältnisse von koexistierenden metasomatischen Fluiden. Die K-F-Richterite sind Cl-frei, obwohl sie mit hochsalinaren Fluiden koexistiert haben. Mg-reiche Amphibole können kein CI einbauen und Fe-reiche Amphibole kein F.
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References
Carmichael ISE (1967) The mineralogy and petrology of the volcanic rocks from the Leucite Hills, Wyoming. Contrib Mineral Petrol 15: 24–66
Dawson JB, Smith JV (1977) The MARID (mica-amphibole-rutile-ilmenite-diopside) suite of xenoliths in kimberlite. Geochim Cosmochim Acta 41: 309–323
Deer WA, Howie RA, Zussman J (1963) Rock-forming minerals, vol 2. Chain silicates. Longmans, Green and Co, London, 379pp
Della Ventura G, Maras A, Parodi GC (1983) Potassium-fluorrichterite from Monte Somma (Campania, Italy). Periodico de Mineralogia 52: 617–630
Erlank AJ, Waters FG, Hawkesworth CJ, Haggerty SE, Allsopp HL, Rickard RS, Menzies MA (1987) Evidence for mande metasomatism in peridotite nodules from the Kimberley pipes, South Africa. In:Menzies MA, Hawkesworth CJ (eds) Mantle metasomatism. Academic Press, London, pp 221–311
Heinrich W (1993) Fluid infiltration through metachert layers at the contact aureole of the Bufa del Diente intrusion: implications for wollastonite formation and fluid immiscibility. Am Mineral 78: 808–814
Jones AP, Smith JV, Dawson JB (1982) Mantle metasomatism in 14 veined peridotites from Bulfontein mine, South Africa. J Geol 90: 435–453
Korzhinskiy MA (1981) Apatite solid solutions as indicators of the fugacity of HCl° and HF' in hydrothermal fluids. Geochim Int 18: 44–60
Menzies MA, Rogers N, Tindle A, Hawkesworth CJ (1987) Metasomatic and enrichment processes in lithospheric peridotites, an effect of asthenosphere-lithosphere interaction. In:Menzies MA, Hawkesworth CJ (eds) Mantle metasomatism. Academic Press, London, pp 313–361
Morrison J (1991) Compositional constraints on the incorporation of Cl into amphiboles. Am Mineral 76: 1920–1930
Mottana A, Griffin WL (1986) Crystal chemistry of two coexisting K-richterites from St. Marcel (Val d'Aosta, Italy). Am Mineral 71: 1426–1433
Ramirez-Fernandez JA, Heinrich W (1991) Geology of the Tertiary Bufa del Diente intrusion and its contact aureole, Sierra de San Carlos, Tamaulipas, Mexico. Zentralblatt für Geologie und Paläontologie (Teil 1) 6: 1519–1531
Thy P (1982) Richterite-arfvedsonite-riebeckite-actinolite assemblage from MARID dikes associated with ultrapotassic magmatic activity in central west Greenland. Terra cognita 2: 247–249
Troll G., Gilbert MC (1972) Fluorine-hydroxyl substitution in tremolite. Am Mineral 57: 1386–1403
Velde D (1978) An aenigmatite-richterite-olivine trachyte from Puu Koae, West Maui, Hawaii. Am Mineral 63: 771–778
Volfinger M, Robert JL, Vielzeuf D, Neiva AMR (1985) Structural control of the chlorine content of OH-bearing silicates (micas and amphiboles). Geochim Cosmochim Acta 49: 37–48
Wagner C, Velde D (1986) The mineralogy of K-richterite-bearing lamproites. Am Mineral 71: 17–37
Zhang YG, Frantz JD (1989) Experimental determination of the compositional limits of immiscibility in the system CaCl2-H2O-CO2 at high temperatures and pressures using synthetic fluid inclusions. Chem Geol 74: 289–308
Zhu C, Sverjensky DA (1991) Partitioning of F-CI-OH between minerals and hydrothermal fluids. Geochim Cosmochim Acta 55:1837–1858
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Heinrich, W. Potassium-fluor-richterite in metacherts from the Bufa del Diente contact-metamorphic auréole, NE-México. Mineralogy and Petrology 50, 259–270 (1994). https://doi.org/10.1007/BF01164609
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DOI: https://doi.org/10.1007/BF01164609