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Mineral chemistry of perpotassic lavas of the Vulsinian district, the Roman Province, Italy

Published online by Cambridge University Press:  05 July 2018

Paul M. Holm
Paul M. Holm*
Affiliation:
Institut for Petrologi, Geologisk Centralinstitut, Øster Voldgade 10, DK-1350 Copenhagen, Denmark
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Synopsis

The Vulsinian district is the largest and northernmost of the Roman Provinces. There is very little modern mineralogical data on the Italian Pliocene to Recent perpotassic alkaline volcanic rocks and this account deals with the compositions of the phenocrysts in the Vulsinian lavas.

The lavas comprise two suites: a leueite-bearing undersaturated series of leucitites, leueite tephrites, leucite phonolites, and trachytes; and a subordinate hy-normative series of mainly trachytes and latites. All lavas are porphyritic with mostly 1–15 vol. % phenoerysts. No cumulates were found. Major elements, and Cr and Ni were determined in the phenocrysts by microprobe analysis and more than 20 trace elements were determined on mineral separates by PIXE.

The undersaturated suite. Ubiquitous clinopyroxene phenoerysts belong to the Di-Hedss series and range from Di97 to Di46. Important amounts of Fe3+ are always present. In the mafic rocks the diopside is chromian, but Ti is low. AI mainly substitutes in the Z positions in all lavas. Only minor Na enrichment occurs with increasing total Fe (0–7 mole % acmite) and thus Ca ferri-Tschermak's component is important. In many of the maric lavas diopside mantles green cores of salite, which has a composition very like the salite of felsic lavas. Leucites contain 5–22 mole % orthoelase in solid solution, but show no systematic variation. Plagioclase, mostly An93-An72, occurs in the felsie lavas, and alkali feldspar only in some phonolites. They both have exceptionally high concentrations of Sr and Ba, with a maximum of 1.3 wt. % SrO and 5.6 wt. % BaO in hyalophanes. Olivine, Fo92-Fo66, occurs in some leucititic lavas in mostly accessory amounts. Phlognpite, magnetite and nepheline are accessory phases of the felsic lavas. Apatite only occur as micro-phenocrysts of the fclsic lavas. Haüyne in trace amounts is found in a few phonolites. Pargasitic amphibole microphenocrysts are found in one lava.

In most marie members diopside ±leuctie ±olivine were liquidus phases. This study does not confirm that these rocks are related by crystal fractionation. In more felsie lavas clinopyroxene (salite-ferrosalite) and leucite are joined by: plagioclase, magnetite ±phlogopite, and Ba-rich alkali feldspar ±haüyne. The felsic rocks are thought to be related by crystal fractionation.

Salitic green cores of phenocrystic pyroxene, mantled by diopside in rocks which also carry normally-zoned diopside, are relicts which provide evidence of either a relatively high PH2O, prior to the crystallization of diopside or magma mixing in the earlier life of these lavas. Pyroxene chemistry points towards low-pressure crystallization (2 kbar), generally in a dry environment.

The hy-normative suite. All lavas have phenocrysts of augite, sanidine, plagioclase, magnetite, biotite, and olivine. The pyroxene is less calcic and has less alumina, but is otherwise rather similar to the salites of the undersaturated suite. Compared to the undersaturated suite, feldspars do not have high Sr and Ba, magnetite has higher TiO2 and olivine crystallized from even the felsic lavas. The pyroxenes show the signs of low-pressure crystallization.

Type
Research Article
Information
Mineralogical Magazine , Volume 46 , Issue 340 , September 1982 , pp. 379 - 386
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1982

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References

Bollingberg, (H.J.) and Bryhni, (I.), 1972. Contrib.Mineral.Petrol. 36, 113–122.CrossRefGoogle Scholar
Boven, (N.I.) and Schairer, (J.F.) 1929. Am.J.Sci. 218, 301–312.Google Scholar
Brooks, (C.K.) and Printslav, (I.), 1978. J.V.Volv.Geotherm.Res. 4, 315–331.CrossRefGoogle Scholar
Buddington, (A.F.) and Lindsley, (D.H.)., 1964. J. Petrol. 5, 310–357.CrossRefGoogle Scholar
Carmichael, (I.S.E.), 1967a). Contrib.Mineral.Petrol. 13, 13–64.Google Scholar
Carmichael, (I.S.E.), 1967b). Contrib.Mineral.Petrol. 15, 24–66.CrossRefGoogle Scholar
Carmichael, (I.S.E.), Turner, (F.J.) and Verhoogen, (J.). 1974. Igneous Petrology. New York (McGraw-Hill).Google Scholar
Cundari, (A.). 1975. Contrib.Mineral, Petrol. 53, 129–144.CrossRefGoogle Scholar
Cundari, (A.). 1979. Contrib.Mineral.Petrol. 70, 9–21.CrossRefGoogle Scholar
Deer, (M.A.), Howie, (R.A.) and Zussman, (J.). 1963. Rock-forming Minerals, Vol. 4. London (Longman).Google Scholar
Dolfi, (D.), Hamilton, (D.L.) and Trigila, (R.). 1978. Prog.Exper.Petrol. 4, 23–24.Google Scholar
Dolfi, (D.) and Trigila, (R.). 1978. Contrib.Mineral.Petrol. 67, 297–304.CrossRefGoogle Scholar
Dolfi, (D.). 1978. Prog. Eaper. Petrol. 4, 18–22.Google Scholar
Fornaeers, (N.). 1972. Recent Contribution of Geochemistry and analytical chemistry (Tugarinev, (A.I.) ed.). New york (John Wiley).Google Scholar
Fudali, (A.F.). 1963. Bull.Geol.Soc.Amer. 74, 1101–1126.CrossRefGoogle Scholar
Gupta, (A.K.). 1972. Am.Mineral. 57, 1242–1259.Google Scholar
Hamilton, (D.L.). l96l). J.Ceol. 69, 321–329.Google Scholar
Henderson, (C.M.B.). 1965. Mineral.Mag. 35, 596–603.Google Scholar
Holm, (P.N.). 1978. Unpublished thesis.Google Scholar
Irvine, (T.N.). 1965. Can.J.Earth Sci. 2, 648–672.CrossRefGoogle Scholar
Kushiro, (I). 1962. Japan J.GooIGeogr.Trans. 33, 213–220.Google Scholar
Kutolin, (V.A.) and Frelova, (V.M.). 1970. Contrib.Mineral.Petrol. 29, 163–179.CrossRefGoogle Scholar
Larson, (E.S.). 1941. Bull.Geol.Soc.Amer. 52, 1841–1856.CrossRefGoogle Scholar
Larson, (L.H.). 1976. J.Petrol. 17, 258–290.CrossRefGoogle Scholar
Leake, (B.I.). 1978. Mineral.Mag. 324, 533–565.CrossRefGoogle Scholar
LeBas, (M.J.). 1962. Am.J.Sci. 260, 267–288.CrossRefGoogle Scholar
Luth, (W.C.). 1967. J. Petrol. 8, 372–416.CrossRefGoogle Scholar
MacKenzie, (W.S.), Richardson, (M.) and Wood, (B.J.). 1974. Bull.Soc.fr. Mineral.Criatallogr. 97, 257–260.Google Scholar
Mathez, (E.A.). 1973. Contrib.Mineral.Petrol. 34, 61–72.CrossRefGoogle Scholar
Matties, (P.P.). 1965. Period. Min. 34, 137–199.Google Scholar
Maxwell, (J.A.). 1968. Rock and Mineral Analysis. New York (Interscience).Google Scholar
O'Hara, (M.J.). 1968. Earth Sci.Rev. 4, 69–133.CrossRefGoogle Scholar
Pichler, (B.). 1970. Itallenische Vulkan Gebiete 1. Soama-Vesuv, Latium, Toscana. Berlin-Stuttgart (Gobi. Borntraoger).Google Scholar
Poldervaart, (A.) and Hess, (H.H.). 1951. J. Geol. 59, 472–489.CrossRefGoogle Scholar
Ruddock, (D.I.) and Hamilton, (D.L.). 1978. Prog.Exper.Petrol. 4, 25–27.Google Scholar
Schnelder, (H.). 1965. Schweiz.Mineral.Petrol.Mitt. 45, 331–456.Google Scholar
Simkin, (T.) and Smith, (J.V.). 1970. J.Geol. 78, 304–325.CrossRefGoogle Scholar
Smith, (J.V.). 1974. Feldspar Minerals. Berlin (Springer).Google Scholar
Sparks, (R.S.J.). 1975. Geol.Rundacha. 64, 497–512.CrossRefGoogle Scholar
Streckeison, (A.). 1967. N.Jb.Miner.Abh. 107, 104–240.Google Scholar
Taylor, (H.P.) and Turi, (B.). 1976. Contrib.Mineral .Petrol. 55, 33–54.CrossRefGoogle Scholar
Thompson, (R.N.). 1974. Mineral.Mag. 39, 768–787.CrossRefGoogle Scholar
Thompson, (R.N.). 1977. Contrib.Mineral-Petrol. 60, 90–108.CrossRefGoogle Scholar
Thornton, (C.P.) and Tuttle, (O.F.). 1960. Am.J.Sci. 258, 664–684.CrossRefGoogle Scholar
Trigila, (R.C.). 1969. Period.Mineral. 38, 625–660.Google Scholar
Turi, (B.) and Taylor, (H.P.). 1976. Contrib.Mineral.Petrol. 55, 1–31.CrossRefGoogle Scholar
Vollmer, (R.). 1975. Nature Phys.Sci. 257, 116–127.CrossRefGoogle Scholar
Vollmer, (R.). 1976. Geochim.Cosmochim-ACt. 40, 283–293.CrossRefGoogle Scholar
Vollmer, (R.). 1977. Contrib.Mineral.Petrol. 60, 109–118.CrossRefGoogle Scholar
Washington, (M.S.). 1906. Carnegie Inst.Washington.Publ. 57.Google Scholar
Watson, (E.B.). 1979. Am.Mineral. 64, 824–829.Google Scholar
Wendlandt, (R.F.). 1978. Carnegie Inst.Y.B. 1977 (Geophys.Lab.), 534-539.Google Scholar