Rocks of the late Neoproterozoic Askaoun pluton (558 ± 2 Ma) located in the Ouzellarh-Sirwa promontory (Anti-Atlas) include magmatic microgranular enclaves (MMEs) ranging from rounded to ovoid in shape, dark and fine grained and generally 5 to 10 cm in size, some reaching a size of 50 cm. They are composed of microdiorite, quartz microdiorite and micromonzodiorite, whereas the felsic host rocks comprise mainly quartz-diorite and amphibole-biotite granodiorite based on mineralogical compositions. The mineral assemblage is similar to those described in their hosting granitoids but with different proportions. In this study composition of minerals is used to describe the nature of the magma and estimate the pressure, temperature and oxygen fugacity at which Askaoun pluton is emplaced. Based on chemistry of biotite Askaoun pluton formed from calc-alkaline magma. Compositions of plagioclase (An 5 - An 29 ); hornblende (Mg ≠= 0.59 - 0.65) and biotite (Mg ≠= 0.49 - 0.55) of MMEs are slightly distinct or similar to those of host rocks (An 7-40 ; hbl Mg ≠= 0.64 - 0.69; Bi Mg ≠= 0.49 - 0.50) which suggest partial to complete equilibration during mafic-felsic magma interaction. The coexisting hornblende and plagioclase (hornblende-plagioclase thermometry), Al content in hornblende (aluminum-in-hornblende barometry) and the assemblage titanite-magnetite-quartz were used to constrain the P, T and fO2 during the crystallization of the parent magmas. The Askaoun pluton was emplaced at temperature ca. 504°C - 633°C and at pressure ca. 0.9 - 4.66 ± 0.6 Kbars (average depth = 6.5 km) from a highly oxidized magma (log fO2 = ?24.8 to ?19.2).
M. Berrahma and M. Delaloye, “Données Géochronologiques Nouvelles sur le Massif Volcanique du Sirwa (AntiAtlas, Maroc),” Journal of African Earth Sciences, Vol. 9, No. 3, 1989, pp. 651-656. doi:10.1016/0899-5362(89)90049-3
J. P. Liégeois, A. Benhallou, A. Azzouni-Sekkal, R. Yahiaoui and B. Bonin, “The Hoggar Swell and Volcanism: Reactivation of the Precambrian Tuareg Shield during Alpine Convergence and West African Cenozoic Volcanism,” In: G. R. Foulger, J. H. Natland, D. C. Presnall, D. L. Anderson, Eds., Plates, Plumes and Paradigms, Geological Society of America Special Paper, Vol. 388, 2005, pp. 379-400. doi:10.1130/0-8137-2388-4.379
M. Regragui,“Les Formation Volcano-Sédimentaire et le Magmatisme Orogénique et Anorogénique du Néoprotérozoique Supérieur et Terminal d’Askaoun (Siroua Occidental, Anti Atlas Central Maroc) Pétrologie, Géochimie et Typologie des Zircons,” Ph.D. Thesis, Université Cadi Ayyad, Marrakech, 1997.
R. J. Thomas, L. P. Chevallier, P. G. Gresse, R. E. Harmer, B. M. Eglington, R. A. Armstrong, C. H. De Beer, J. E. J. Martini, G. S. De Kock, P. H. Macey and B. A. Ingram, “Precambrian Evolution of the Sirwa Window, AntiAtlas Orogen, Morocco,” Precambrian Research, Vol. 118, No. 1-2, 2002, pp. 1-57. doi:10.1016/S0301-9268(02)00075-X
R. J. Thomas, A. Fekkak, N. Ennih, E. Errami, S. C. Loughlin, P. G. Gresse, L. P. Chevallier and J. P. Liégeois, “A New Lithostratigraphic Framwork for the Anti-Atlas Orogen, Morocco,” Journal of African Earth Sciences, Vol. 39, No. 3-5, 2004, pp. 217-226. doi:10.1016/j.jafrearsci.2004.07.046
A. Toummite, J. P. Liégeois, D. Gasquet , O. Bruguier, E. H. Beraaouz and M. Ikenne, “Field, Geochemistry and Sr-Nd Isotopes of the Pan-African Granitoids from the Tifnoute Valley (Sirwa, Anti-Atlas, Morocco): A PostCollisional Event in a Metacratonic Setting,” Mineralogy and Petrology, Special Issue: Gondwana Collision, 2012.
J. M. Hammarstrom and E. A. Zen, “Aluminium in Hornblende: An Empirical Igneous Géobaromètre,” American Mineralogist, Vol. 71, No. 11-12, 1986, pp. 1297-1313.
L. S. Hollister, G. C. Grissom, E. K. Peters, H. H. Stowell and V. B. Sisson, “Confirmation of the Empirical Calibration of Al in Hornblende with Pressure of Solidification of Calc-Alkaline Plutons,” American Mineralogist, Vol. 72, No. 3-4, 1987, pp. 231-239.
M. C. Johnson and M. J. Rutherford, “Experimental Calibration of the Aluminium-in-Hornblende Geobarometer with Application to Long Valley Caldera (California) Volcanic Rocks,” Geology, Vol. 17, No. 9, 1989, pp. 837-841. doi:10.1130/0091-7613(1989)017 2.3.CO;2
J. Blundy and T. J. Holland, “Calcic Amphibole Equilibria and a New Amphibole-Plagioclase Geothermometer,” Contributions to Mineralogy and Petrology, Vol. 104, No. 2, 1990, pp. 208-224. doi:10.1007/BF00306444
M. W. Schmidt, “Amphibole Composition in Tonalite as a Function of Pressure: An Experimental Calibration of the Al-in-Hornblende Barometer,” Contributions to Mineralogy and Petrology, Vol. 110, No. 2-3, 1992, pp. 304-310. doi:10.1007/BF00310745
T. Holland and J. Blundy, “Non-Ideal Interactions in Calcic Amphiboles and Their Bearing on Amphibole-Plagioclase Thermometry,” Contributions to Mineralogy and Petrology, Vol. 116, No. 4, 1994, pp. 433-447. doi:10.1007/BF00310910
J. L. Anderson and D. R. Smith, “The Effects of Temperature and fO2 on the Al-in-Hornblende Barometer,” American Mineralogist, Vol. 80, No. 5-6, 1995, pp. 549559. doi:10.1017/S0263593300006544
J. L. Anderson, “Status of Thermobarometry in Granitic Batholiths,” Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 87, No. 1-2, 1996, pp. 125-138.
F. Ridolfi, A. Renzulli and M. Puerini, “Stability and Chemical Equilibrium of Amphibole in Calc-Alkaline Magmas: An Overview, New Thermobarometric Formulations and Application to Subduction-Related Volcanoes,” Contributions to Mineralogy and Petrology, Vol. 160, No. 1, 2010, pp. 45-66. doi:10.1007/s00410-009-0465-7
B. E. Leake, “On Aluminous and Edenitic Amphiboles,” Mineralogical Magazine, Vol. 38, No. 296, 1971, pp. 389-407. doi:10.1180/minmag.1971.038.296.01
B. E. Leake, “Nomenclature of Amphiboles: Report of the Subcommittee on Amphiboles of the International Commission on New Minerals and Mineral Names,” Mineralogical Magazine, Vol. 61, No. 405 1997, pp. 295-321. doi:10.1180/minmag.1997.061.405.13
A. Mogessie, K. Ettinger, B. E. Leake and R. Tessardi, “AMPHIMA97: A Hypercard Program to Determine the Name of an Amphibole from Electron Microprobe and Wet Chemical Analyses,” Computers and Geosciences, Vol. 27, No. 10, 2001, pp. 1169-1178. doi:10.1016/S0098-3004(01)00034-6
W. A. Deer, R. A. Howie and J. Zussman, “An Introduction to Rock-Forming Minerals,” 17th Edition, Longman Ltd., London, 1966, p. 528.
E. Zen, “Tectonic significance of high pressure plutonic rocks in the Western Cordillera of North America,” In: W. G. Ernst, Ed., Metamorphism and Crustal Evolution of the Western United States, Prentice-Hall, Engelwood Cliffs, 1988, pp. 41-67.
A. Abdel-Rahman, “Nature of Biotites from Alkaline, Calcalkaline and Peraluminous Magmas,” Journal of Petrology, Vol. 35, No. 2, 1994, pp. 525-541.
M. Barriere and J. Cotton, “Biotites and Associated Minerals as Markers of Magmatic Fractionation and Deuteric Equilibration in Granites,” Contributions to Mineralogy and Petrology, Vol. 70, No. 2, 1979, pp. 183-192. doi:10.1007/BF00374447
G. A. R. De Albuquerque, “Geochemistry of Biotites from Granitic Rocks, Northern Portugal,” Geochimica et Cosmochimica Acta, Vol. 37, No. 2, 1973, pp. 1779-802. doi:10.1016/0016-7037(73)90163-4
M. D. Foster, “Interpretation of the Composition of Trioctahedral Micas,” US Government Printing Office, Washington DC, 1960, pp. 1-49.
M. L. Kabesh and A. M. Refaat, “On the Chemistry of Biotites and Variation of Ferrous-Ferric Ratios in the Granitic Rocks of Umm Naggat Stock, Egypt,” Neues Jahrbuch fur Mineralogy Abhandlungen, Vol. 124, No. 1, 1975, pp. 47-60.
F. Moazamy, “Application of Biotite Composition in Determination of Tectonic Setting of Granitoids of BorujerdHamedan,” M.S.C. Thesis, Tarbiat Moalem University of Iran, Tehran, 2006.
H. Nachit, A. Ibhi, E. H. Abia and M. Ben Ohoud, “Discrimination between Primary Magmatic Biotites, Reequilibrated Biotites and Neoformed Biotites,” Comptes Rendus Geoscience, Vol. 337, No. 16, 2005, pp. 1415-1420. doi:10.1016/j.crte.2005.09.002
A. M. R. Neiva, “The Geochemistry of Biotites from Granites of Northern Portugal with Special Reference to Their Tin Content,” Mineralogical Magazine, Vol. 40, No. 313, 1976, pp. 453-66.
S. R. Nockolds, “The Relation between Chemical Composition and Paragenesis in the Biotite Micas of Igneous Rocks,” American Journal of Science, Vol. 245, No. 7, 1947, pp. 401-420. doi:10.2475/ajs.245.7.401
E. S. Sapountzis, “Biotites from the Sithonia Igneous Complex (North Greece),” Neues Jahrbuch fur Mineralogy Abhandlungen, Vol. 126, No. 3, 1976, pp. 327-341.
A. T. Shabbani and A. Lalonde, “Composition of Biotite from Granitic Rocks of the Canadian Appalachian: A Potential Tectonomagmatic Indicator?” The Canadian Mineralogist, Vol. 41, No. 6, 2003, pp. 1381-1396. doi:10.2113/gscanmin.41.6.1381
J. A. Speer, “Micas in Igneous Rocks,” In: S.W. Bailey, Ed., Micas: Reviews in Mineralogy Volume 13, Mineralogical Society of America, Washington DC, 1984, pp. 299-356.
E. Stein and E. Dietl, “Hornblende Thermobarometry of Granitoids from the Central Odenwald (Germany) and Their Implications for the Geotectonic Development of the Odenwald,” Mineralogy and Petrology, Vol. 72, No. 1-3, 2001, pp. 185-207. doi:10.1007/s007100170033
W. G. Ernst, “Paragenesis and Thermobarometry of Camphiboles in the Barcroft Granodioritic Pluton, Central White Mountains, Eastern California,” American Mineralogist, Vol. 87, No. 4, 2002, pp. 478-490.
M. J. Rutter, S. R. Van der Laan and P. J. Wyllie, “Experimental Data for a Proposed Empirical Igneous Geobarometer: Aluminium in Hornblende at 10 kbar Pressure,” Geology, Vol. 17, No. 10, 1989, pp. 897-900. doi:10.1130/0091-7613(1989)017 2.3.CO;2
J. J. Ague and M. T. Brandon, “Tilt and Northward Offset of Cordilleran Batholiths Resolved Using Igneous Barometry,” Nature, Vol. 360, No. 6400, 1992, pp. 146-149. doi:10.1038/360146a0
J. J. Ague and M. T. Brandon, “Regional Tilt of the Mount Stuart Batholith, Washington, Determined Using Aluminum-in-Hornblende Barometry: Implications for Northward Translation of Baja British Columbia,” Geological Society of American Bulletin, Vol. 108, No. 4, 1996, pp. 471-488. doi:10.1130/0016-7606(1996)108 2.3.CO;2
S. H. Zhang, Y. Zhao and B. Song, “Hornblende Thermobarometry of the Carboniferous Granitoids from the Inner Mongolia Paleouplift: Implication for the Tectonic Evolution of the Northern Margin of the North China Block,” Mineralogy and Petrology, Vol. 87, No. 1-2, 2006, pp. 123-141. doi:10.1007/s00710-005-0116-2
E. D. Ghent, J. Nicholls, P. S. Siminy, H. H. Sevigny and M. Z. Stout, “Hornblende Geobarometry of the Nelson Batholith, Southeastern British Columbia: Tectonic Implications,” Canadian Journal of Earth Science, Vol. 28, No. 12, 1991, pp. 1982-1991. doi:10.1139/e91-180
A. J. Tulloch and G. A. Challis, “Emplacement Depths of Paleozoic-Mesozoic Plutons from Western New Zealand Estimated by Hornblende-Al Geobarometry,” New Zealand Journal of Geology and Geophysics, Vol. 43, No. 4, 2000, pp. 555-567. doi:10.1080/00288306.2000.9514908
S. E. Haggerty, “Opaque Mineral Oxides in Terrestrial Igneous Rocks,” Mineralogical Society of America Short Course Notes 3, Washington DC, 1976, pp. 101-300.
M. Enami, K. Suzuki, J. G. Liou and D. K. Bird, “Al-Fe3+ and F-OH Substitutions in Titanite and Constrains on Their P-T Dependence,” European Journal of Mineralogy, Vol. 5, No. 2, 1993, pp. 231-291.
D. R. Wones, “Significance of the Assemblage Titanite + Magnetite + Quartz in Granitic Rocks,” American Mineralogist, Vol. 74, 1989, pp. 744-749.
A. Michard, O. Saddiqi, A. Chlouan and D. F. De Lamote, “Continental Evolution: The Geology of Morocco, Structures, Stratigraphy and Tectonics of the Africa-AtlanticMediterranean Triple Junction,” Springer, Berlin, 2008, p. 405.
P. G. Gresse, C. H. De Beer, G. S. De Kock, R.J. Thomas, L.P. Chevallier, “Carte et Notice Explicative de la Carte Géologique du Maroc au 1/50 000 Feuille Tachoukacht,” Notes et Mémoires du Service Géologique du Maroc, No. 392, 2000.
G. Choubert, “Carte Géologique du Maroc au 1/500 000, feuille Marrakech,” Notes et Mémoires du Service Géologique du Maroc, Vol. 70, 1957.