Jump to ContentJump to Main Navigation
Show Summary Details
More options …

American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian

IMPACT FACTOR 2018: 2.631

CiteScore 2018: 2.55

SCImago Journal Rank (SJR) 2018: 1.355
Source Normalized Impact per Paper (SNIP) 2018: 1.103

See all formats and pricing
More options …
Volume 102, Issue 10


Kiglapait mineralogy V: Feldspars in a hot, dry magma

S.A. Morse
  • Corresponding author
  • Department of Geosciences, University of Massachusetts, 611 North Pleasant Street, Amherst, Massachusetts, 01003-9297, U.S.A
  • Email
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
Published Online: 2017-10-02 | DOI: https://doi.org/10.2138/am-2017-6098


The lithology of the 1.305 Ga Kiglapait intrusion is dominated by a Lower Zone of troctolite, succeeded by an Upper Zone of olivine gabbro, ferrodiorite, and syenite with olivine composition of pure fayalite. The feldspar composition of the intrusion varies from An68 to An9 over a thickness of 8.4 km from the base to a sandwich horizon under an Upper Border Zone. The anhydrous nature of the Kiglapait syenites is shown by their high temperature, by the loss of minor biotite up-stratigraphy in the intrusion, and the absence of amphibole. The end-stage feldspar of the Kiglapait syenites is that of a solidus embedded in a solvus in a 3 kbar eutectic at 1000 °C. The end-member assemblage at temperature and pressure is invariant. The final bulk composition is relatively An-rich—An ~11%—with a composition of XOr = 1/3 when projected to the Ab-Or sideline. The experimental feldspar solvus when corrected for the effects of An and Ba and referred to 3 kbar penetrates the solidus and fits the experimental tie lines. These conditions precede a stage of local coarsening under subsolidus conditions that is found in colloform symplectites invading mesoperthite. The oligoclase-orthoclase symplectites are iso-compositional with their host mesoperthites. The coarsening is assumed to be related to a plausibly F-rich vapor phase that is locally consumed with time. The observed phase compositions indicate the end of exsolution at ~800 °C at 3 kbar on the binodal solvus.

Keywords: Feldspar compositions; Kiglapait Intrusion; chemistry; textures; exsolution; symplectite; coarsening; solvus; syenites; cooling history

References cited

  • Berg, J.H. (1977) Dry granulite mineral assemblages in the contact aureole of the Nain Complex, Labrador. Contributions Mineralogy Petrology, 64, 32–52.Google Scholar

  • Berg, J.H., and Docka, J.A. (1983) Geothermometry in the Kiglapait aureole, Labrador. American Journal of Science, 283, 414–434.Google Scholar

  • Bollmann, W., and Nissen, H.-U. (1968) A study of optimal phase boundaries: the case of exsolved alkali feldspars. Acta Crystallographica, A24, 546–557.Google Scholar

  • Bowen, N.L. (1915) The crystallization of haplobasaltic, haplodioritic, and related magmas. American Journal of Science, 40, 161–185.Google Scholar

  • Bowen, N.L. (1945) Phase equilibria bearing on the origin and differentiation of alkaline rocks. American Journal of Science, 243a, 75–89.Google Scholar

  • Goldsmith, J.R. (1980) Melting and breakdown reactions of anorthite at high pressures and temperatures. American Mineralogist, 65, 272–284.Google Scholar

  • Fuhrman, M.L., and Lindsley, D.H. (1988) Ternary-feldspar modeling and thermometry. American Mineralogist, 73, 201–215.Google Scholar

  • Fuhrman, M.L., Frost, B.R., and Lindsley, D.H. (1988) Crystallization conditions of the Sybille Monzosyenite, Laramie Anorthosite Complex, Wyoming. Journal of Petrology, 29, 699–729.Google Scholar

  • Holness, M.B. (2007) Textural immaturity of cumulates as an indicator of magma chamber processes: infiltration and crystal accumulation in the Rum Eastern Layered Intrusion. Journal of the Geological Society of London, 164, 529–539.Google Scholar

  • Holness, M.B., Tegner, C., Nielsen, T.F.D., Stripp, G., and Morse, S.A. (2007) A textural record of solidification and cooling in the Skaergaard Intrusion, East Greenland. Journal of Petrology, 48, 2359–2377.Google Scholar

  • Hovis, G.L., Delbove, F., and Roll Bose, M. (1991) Gibbs energies and entropies of K-Na mixing for alkali feldspars from phase equilibrium data: Implications for feldspar solvi and short-range order. American Mineralogist, 76, 913–927.Google Scholar

  • Huntington, H.D. (1979) Kiglapait mineralogy I: Apatite, biotite, and volatiles. Journal of Petrology, 20, 625–652.Google Scholar

  • Johannsen, A. (1939) A Descriptive Petrography of the Igneous Rocks, 2nd ed., vol. 1. 318 pp. University of Chicago Press.Google Scholar

  • Lange, R.A. (2003) The fusion curve of albite and the compressibility of NaAlSi3O8 liquid with pressure. American Mineralogist, 68, 477–493.Google Scholar

  • Morse, S.A. (1969a) The Kiglapait Layered Intrusion, Labrador. Geological Society America Memoir 112, 204 pp, .CrossrefGoogle Scholar

  • Morse, S.A. (1969b) Feldspars. Carnegie Institution of Washington Year Book, 67, 120–126.Google Scholar

  • Morse, S.A. (1970) Alkali feldspars with water at 5 kb pressure. Journal of Petrology, 11, 221–251.Google Scholar

  • Morse, S.A. (1978) Test of plagioclase dispersion method and rapid probe analysis. American Mineralogist, 63, 768–770.Google Scholar

  • Morse, S.A. (1979) Kiglapait geochemistry II: Petrography. Journal of Petrology, 20, 591–624.Google Scholar

  • Morse, S.A. (1980) Kiglapait mineralogy II: Fe-Ti oxide minerals and the activities of oxygen and silica. Journal of Petrology, 21, 685–719.Google Scholar

  • Morse, S.A. (1981a) Kiglapait geochemistry III: Potassium and rubidium. Geochimica et Cosmochimica Acta, 45, 163–180.Google Scholar

  • Morse, S.A. (1981b) Kiglapait geochemistry IV: The major elements. Geochimica et Cosmochimica Acta, 45, 461–479.Google Scholar

  • Morse, S.A. (1983) Strontium isotope fractionation in the Kiglapait intrusion. Science, 220, 193–195.Google Scholar

  • Morse, S.A. (1984) Cation diffusion in plagioclase feldspar. Science, 225, 504–505.Google Scholar

  • Morse, S.A. (1994) Basalts and Phase Diagrams. Krieger, Florida, 493 pp.Google Scholar

  • Morse, S.A. (1997) Binary solutions and the lever rule revisited. Journal of Geology, 105, 471–482.Google Scholar

  • Morse, S.A. (2000) Linear partitioning in binary solutions. Geochimica et Cosmochimica Acta, 64, 2309–2319.Google Scholar

  • Morse, S.A. (2012) Plagioclase An range and residual porosity in igneous cumulates of the Kiglapait Intrusion. Journal of Petrology, 53, 891–918.Google Scholar

  • Morse, S.A. (2013) Solidification of trapped liquid in rocks and crystals. American Mineralogist, 98, 888–896.Google Scholar

  • Morse, S.A. (2014) Plagioclase fractionation in troctolitic magma. Journal of Petrology, 55, 2403–2418.Google Scholar

  • Morse, S.A. (2015a) Linear partitioning in binary solutions: A review with a novel partitioning array. American Mineralogist, 100, 1021–1032.Google Scholar

  • Morse, S.A. (2015b) Kiglapait Intrusion, Labrador. In B. Charlier, O. Namur, R. Latypov, and C. Tegner, Eds., Layered Intrusions, p. 589–648. Springer.Google Scholar

  • Morse, S.A., and Allaz, J. (2013) Experimental partitioning of Sr and Ba in Kiglapait feldspars. American Mineralogist, 98, 2197–2200.Google Scholar

  • Morse, S.A., and Brady, J.B. (2017a) Thermal history of the Upper Zone of the Kiglapait intrusion. Journal of Petrology, in press.Google Scholar

  • Morse, S.A., and Brady, J.B. (2017b) The system fayalite-albite-anorthite and the syenite problem. American Mineralogist, 102, 2062–2068.Google Scholar

  • Morse, S.A., and Nolan, K.M. (1984) Origin of strongly reversed rims on plagioclase in cumulates. Earth and Planetary Science Letters, 68, 485–498.Google Scholar

  • Morse, S.A., and Ross, M. (2004) Kiglapait mineralogy IV: The augite series. American Mineralogist, 89, 1380–1395.Google Scholar

  • Morse, S.A., Brady, J.B., and Sporleder, B.A. (2004) Experimental petrology of the Kiglapait intrusion: Cotectic trace for the Lower Zone at 5kb in graphite. Journal of Petrology, 45, 2225–2259.Google Scholar

  • Nekvasil, H., and Lindsley, D.H. (1990) Termination of the 2 feldspar + liquid curve in the system Ab-Or-An-H2O at low H2O contents. American Mineralogist, 75, 1071–1079.Google Scholar

  • Parsons, I. (1979) The Klokken gabbro-syenite complex, South Greenland: Cryptic variation and origin of inversely graded layering. Journal of Petrology, 20, 653–694.Google Scholar

  • Parsons, I., and Brown, W.L. (1988) Sidewall crystallization in the Klokken intrusion: zoned ternary feldspars and coexisting minerals. Contributions to Mineralogy and Petrology, 98, 431–443.Google Scholar

  • Parsons, I., Fitz Gerald, J.D., and Lee, M.R. (2015) Routine characterization and interpretation of complex alkali feldspar intergrowths. American Mineralogist, 100, 1277–1303.Google Scholar

  • Peterson, A.L. (1999) Quest for the liquid line of descent of the Upper Zone of the Kiglapait intrusion, Labrador, Canada: an experimental study. M.S. thesis, University of Massachusetts, 80 pp.Google Scholar

  • Philpotts, A.R., Brustman, C.M., Shi, J., Carlson, W.D., and Denison, C. (1999) Plagioclase chain networks in slowly cooled basalt magma. American Mineralogist, 84, 1819–1829.Google Scholar

  • Ryan, A.B. (1990) Preliminary geological map of the Nain Plutonic Suite and surrounding rocks (Nain-Nutak, NTS 14 SW). Newfoundland Department of Mines and Energy, Geological Survey Branch, Map 90-44, scale 1:500,000.Google Scholar

  • Smith, J.V., and Brown, W.L. (1988) Feldspar Minerals: Volume 1: Crystal Structures, Physical, Chemical, and Microtextural Properties. Springer-Verlag, Berlin-Heidelberg, 828 pp.Google Scholar

  • Speer, J.A., and Ribbe, P.H. (1973) The feldspars of the Kiglapait intrusion, Labrador. American Journal of Science 273-A, 468–478.Google Scholar

  • Sporleder, B.A. (1998) Liquid line of descent of the Lower Zone of the Kiglapait Intrusion, Labrador, Canada: An experimental study. M.S. thesis, University of Massachusetts, 93 pp.Google Scholar

  • Stacey, F.D., and Davis, P.M. (2009) Physics of the Earth, 4th ed. Cambridge University Press, 532 p.Google Scholar

  • Stewart, D.B., and Roseboom, E.H. Jr. (1962) Lower temperature termination of the three-phase region plagioclase-alkali feldspar-liquid. Journal of Petrology, 3, 280–315.Google Scholar

  • Thompson, J.B. Jr., and Waldbaum, D.R. (1969) Mixing properties of sanidine crystalline solutions: III. Calculations based on two-phase data. American Mineralogist, 54, 811–838.Google Scholar

  • Tuttle, O.F., and Bowen, N.L. (1958) Origin of granite in the light of experimental studies in the system NaAlSi3O8-KAlSi3O8-SiO2-H2O. Geological Society of America Memoir, 74, 153 pp.Google Scholar

  • Upton, B.G.J. (2013) Tectono-magmatic evolution of the younger Gardar southern rift, South Greenland. Geological Survey of Denmark and Greenland Bulletin 29, 124 pp.Google Scholar

  • Waldbaum, D.R., and Thompson, J.B. Jr. (1969) Mixing properties of sanidine crystalline solutions: IV. Phase diagrams from equations of state. American Mineralogist, 54, 1274–1298.Google Scholar

  • Xue, S., and Morse, S.A. (1993) Geochemistry of the Nain massif anorthosite, Labrador: Magma diversity in five intrusions. Geochimica et Cosmochimica Acta, 57, 3925–3948.Google Scholar

  • Yoder, H.S., Stewart, D.B., and Smith, J.R. (1957) Ternary feldspars. Carnegie Institution of Washington Yearbook, 56, 206–214.Google Scholar

  • Yund, R.A., and Davidson, P. (1978) Kinetics of lamellar coarsening in cryptoperthites. American Mineralogist, 63, 470–477.Google Scholar

About the article

Received: 2017-02-03

Accepted: 2017-05-27

Published Online: 2017-10-02

Published in Print: 2017-10-26

Citation Information: American Mineralogist, Volume 102, Issue 10, Pages 2084–2095, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am-2017-6098.

Export Citation

© 2017 by Walter de Gruyter Berlin/Boston.

Comments (0)

Please log in or register to comment.
Log in