Diopside phenocrysts from nephelinite lavas, Napak volcano, eastern Uganda: Evidence for magma mixing

Canadian Mineralogist

Volumn 34, Issue 2, 1996, Pages 411-421

  Simonetti, Antonio ^a,b   Shore, Mark ^c   Bell, Keith ^b  

^a MAX PLANCK INSTITUTE FOR CHEMISTRY   (Germany)

^b CARLETON UNIVERSITY   (Canada)

^c UNIVERSITY OF OTTAWA   (Canada)

Author keywords

Bimodality; Diopside; Magma mixing; Napak; Nephelinite; Uganda

Indexed keywords

CLINOPYROXENE; DIOPSIDE; MAGMA MIXING; MINERAL CHEMISTRY; NEPHELINITE; PHENOCRYST;

UGANDA, NAPAK VOLCANO;

EID: 0029730202     PISSN: 00084476     EISSN: None     Source Type: Journal    
DOI: None     Document Type: Article

References (53)

1. ANDERSON, A.T., JR. (1983): Oscillatory zoning of plagioclase: Nomarski interference contrast microscopy of etched polished sections. Am. Mineral. 68, 125-129.
2. AOKI, K. & KUSHIRO, I. (1968): Some clinopyroxenes from ultramafic inclusions in Dreiser Weiher, Eifel. Contrib. Mineral. Petrol. 18, 326-337.
3. _ & SHIBA, I. (1973): Pyroxenes from lherzolite inclusions of Itinomegata, Japan. Lithos 6, 41-51.
4. BARTON, M. & VAN BERGEN, M.J. (1981): Green clinopyroxenes and associated phases in a potassium-rich lava from the Leucite Hills, Wyoming. Contrib. Mineral. Petrol. 77, 101-114.
5. BREY, G.P. (1978): Origin of olivine melilitites - chemical and experimental constraints. J. Volcanol. Geotherm. Res. 3, 61-88.
6. 2 at high pressures and the petrogenesis of an olivine melilitite magma. Contrib. Mineral. Petrol. 61, 141-162.
7. BROOKS, C.K. & PRINTZLAU, I. (1978): Magma mixing in mafic alkaline volcanic rocks: the evidence from relict phenocryst phases and other inclusions. J. Volcanol. Geotherm. Res. 4, 315-331.
8. BULTITUDE, R.J. & GREEN, D.H. (1971): Experimental study of crystal-liquid relationships at high pressures in olivine nephelinite and basanite compositions. J. Petrol. 12, 121-147.
9. CLARK, A.H., PEARCE, T.H., ROEDER, P.L. & WOLFSON, I. (1986): Oscillatory zoning and other microstructures in magmatic olivine and augite: Nomarski interference contrast observations on etched polished surfaces. Am. Mineral. 71, 734-741.
10. COHEN, R.S., O'NIONS, R.K. & DAWSON, J.B. (1984): Isotope geochemistry of xenoliths from East Africa: implications for development of mantle reservoirs and their interaction. Earth Planet. Sci. Lett. 68, 209-220.
11. DAWSON, J.B. (1987): Metasomatized harzburgites in kimberlite and alkaline magmas: enriched restites and "flushed" Iherzolites. In Mantle Metasomatism (M.A. Menzies & C.J. Hawkesworth, eds.). Academic Press, London, U.K. (125-144).
12. DEER, W.A., HOWIE, R.A. & ZUSSMAN, J. (1992): An Introduction to the Rock-Forming Minerals (second ed.) Longman Scientific & Technical, Essex, U.K.
13. DOBOSI, G. & FODOR, R.V. (1992): Magma fractionation, replenishment, and mixing as inferred from green-core clinopyroxenes in Pliocene basanite, southern Slovakia. Lithos 28, 133-150.
14. DONALDSON, C.H., DAWSON, J.B., KANARIS-SOTIRIOU, R., BATCHELOR, R.A. & WALSH, J.N. (1987): The silicate lavas of Oldoinyo Lengai, Tanzania. Neues Jahrbuch Mineral., Abh. 156, 247-279.
15. 3+ concentrations in ferromagnesian silicates and oxides from microprobe analyses, using stoichiometric criteria. Mineral. Mag. 51, 431-435.
16. DUDA, A. & SCHMINCKE, H.-U. (1985): Polybaric differentiation of alkali basaltic magmas: evidence from green-core clinopyroxenes (Eifel, FRG). Contrib. Mineral. Petrol. 91, 340-353.
17. EGGLER, D.H. (1989): Carbonatites, primary melts, and mantle dynamics. In Carbonatites: Genesis and Evolution (K. Bell, ed.). Unwin Hyman, London, U.K. (561-579).
18. FREESTONE, I.C. & HAMILTON, D.L. (1980): The role of liquid immiscibility in the genesis of Carbonatites: an experimental study. Contrib. Mineral. Petrol. 73, 105-117.
19. KING, B.C. (1949): The Napak area of southern Karamoja, Uganda. Mem. Geol. Surv. Uganda 5, 1-57.
20. KJARSGAARD, B.A. & HAMILTON, D.L. (1988): Liquid immiscibility and the origin of alkali-poor carbonatites. Mineral. Mag. 52, 43-55.
21. _ & _ (1989a): Carbonatite origin and diversity. Nature 338, 547-548.
22. _ & _ (1989b): Melting experiments on Shombole nephelinites: silicate/carbonate immiscibility, phase relations and the liquid line of descent. Geol. Assoc. Can. - Mineral. Assoc. Can., Program Abstr. 14, A50.
23. _ & _ (1989c): The genesis of carbonatites by immiscibility. In Carbonatites: Genesis and Evolution (K. Bell, ed.). Unwin Hyman, London, U.K. (388-404).
24. _ & PETERSON, T.D. (1991): Nephelinite-carbonatite liquid immiscibility at Shombole volcano, East Africa: petrographic and experimental evidence. Mineral. Petrol. 43, 293-314.
25. 2 at pressures up to 1 kilobar. Am. J. Sci. 264, 234-255.
26. 2O and its bearing on the genesis of carbonatites. Am. J. Sci. 266, 932-967.
27. 2O. Am. J. Sci. 273, 465-487.
28. KRAMM, U. (1994): Isotope evidence for ijolite formation by fenitization: Sr-Nd data of ijolites from the type locality Iivaara, Finland. Contrib. Mineral. Petrol. 115, 279-286.
29. LE BAS, M.J. (1987): Nephelinites and carbonatites. In Alkaline Igneous Rocks (J.G. Fitton & B.G.J. Upton, eds.). Blackwell, London, U.K. (53-83).
30. _ (1989): Diversification of carbonatite. In Carbonatites: Genesis and Evolution (K. Bell, ed.). Unwin Hyman, London, U.K. (428-447).
31. MEYER, H.O.A. & MITCHELL, R.H. (1988): Sapphire-bearing ultramafic lamprophyre from Yogo, Montana: a ouachitite. Can. Mineral. 26, 81-88.
32. MITCHELL, R.H. (1980): Pyroxenes of the Fen alkaline complex, Norway. Am. Mineral. 65, 45-54.
33. OLAFSSON, M. & EGGLER, D.H. (1983): Phase relations of amphibole, amphibole-carbonate, and phlogopite-carbonate peridotite: petrologic constraints on the asthenosphere. Earth Planet. Sci. Lett. 64, 305-315.
34. PEARCE, T.H. & KOLISNIK, A.M. (1990): Observation of plagioclase zoning using interference imaging. Earth-Sci. Rev. 29, 9-26.
35. PETERSON, T.D. (1989a): Peralkaline nephelinites. I. Comparative petrology of Shombole and Oldoinyo L'engai, East Africa. Contrib. Mineral. Petrol. 101, 458-478.
36. _ (1989b): Peralkaline nephelinites II. Low pressure fractionation and the hypersodic lavas of Oldoinyo L'engai. Contrib. Mineral. Petrol. 102, 336-346.
37. PLATT, R.G. & EDGAR, A.D. (1972): The system nepheline - diopside - sanidine and its significance to the genesis of melilite- and olivine-bearing alkaline rocks. J. Geol. 80, 224-236.
38. PRINGLE, G.J. (1989): EDDI: A FORTRAN computer program to produce corrected microprobe analyses of minerals using an energy dispersive X-ray spectrometer. Geol. Surv. Can., Open-File Rep. 2127.
39. REEDER, R.J., FAGIOLI, R.O. & MEYERS, W.J. (1990): Oscillatory zoning of Mn in solution-grown calcite crystals. Earth-Sci. Rev. 29, 39-46.
40. ROEDER, P.L. & EMSLIE, R.F. (1970): Olivine-liquid equilibrium. Contrib. Mineral. Petrol. 29, 275-289.
41. SANTACROCE, R., BERTAGNINI, A., CIVETTA, L., LANDI, P. & SBRANA, A. (1993): Eruptive dynamics and petrogenetic processes in a very shallow magma reservoir: the 1906 eruption of Vesuvius. J. Petrol. 34, 383-425.
42. SCHAIRER, J.F. & YODER, H.S., JR. (1960): The nature of residual liquids from crystallization, with data on the system nepheline - diopside - silica. Am. J. Sci. 258A, 273-283.
43. SCHULZE, D.J. (1987): Megacrysts from alkalic volcanic rocks. In Mantle Xenoliths (P.H. Nixon, ed.). John Wiley & Sons, Chichester, U.K. (433-451).
44. SHIMIZU, N. (1990): The oscillatory trace element zoning of augite phenocrysts. Earth-Sci. Rev. 29, 27-37.
45. SIMONETTI, A. & BELL, K. (1993): Isotopic disequilibrium in clinopyroxenes from nephelinitic lavas, Napak volcano, eastern Uganda. Geology 21, 243-246.
46. _ & _ (1994): Nd, Pb and Sr isotopic data from the Napak carbonatite - nephelinite centre, eastern Uganda: an example of open-system crystal fractionation. Contrib. Mineral. Petrol. 115, 356-366.
47. THOMPSON, R.N. (1973): Oscillatory and sector zoning in augite from a Vesuvian lava. Carnegie Inst. Wash. Yearbook 72, 463-470.
48. _ (1974): Some high-pressure pyroxenes. Mineral. Mag. 39, 768-787.
49. TURNER, J.S. & CAMPBELL, I.H. (1986): Convection and mixing in magma chambers. Earth-Sci. Rev. 23, 255-352.
50. UPTON, B.G.J., MITCHELL, R.H., LONG, A. & ASPEN, P. (1992): Primitive olivine melanephelinite dykes from the Orkney Islands, Scotland. Geol. Mag. 129, 319-324.
51. WALLACE, M.E. & GREEN, D.H. (1988): An experimental determination of primary carbonatite magma composition. Nature 335, 343-346.
52. WASS, S.Y. (1979): Multiple origins of clinopyroxene in alkalic basaltic rocks. Lithos 12, 115-132.
53. 2 vapour: results and implications for the formations of light rare earth-enriched rocks. Contrib. Mineral. Petrol. 69, 409-419.