Abstract
Megacrysts of titanian pyrope, high-Ti bronzite, sub-calcic diopside to augite, and phlogopite in an alnöitic breccia, Malaita, Solomon Islands, have compositional features which distinguish them from silicates in kimberlites. Particularly important is the high content of Al2O3 in the Malaita silicates, which may reflect the higher Al2O3 content of alnöite than kimberlite. The phlogopite megacrysts fall into two populations, one richer in Mg and Cr, and lower in Ti, than the other. The pyroxenes may also fall into two groups characterized by high and low Mg, Cr and Ni. Two stages of crystallization may be responsible.
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Allen, J.B., Deans, T.: Ultrabasic eruptives with alnöitic-kimberlitic affinities from Malaita, Solomon Islands. Mineral. Mag.34, 16–34 (1965)
Chapman, N.A.: Inclusions and megacrysts from undersaturated tuffs and basanites, East Fife, Scotland. J. Petrol.17, 472–498 (1976)
Danchin, R.V., Ferguson, J., McIver, J.R., Nixon, P.H.: The composition of late-stage kimberlite liquids as revealed by nucleated autoliths. Phys. Chem. Earth9, 235–245 (1975)
Dawson, J.B., Stephens, W.E.: Statistical classification of garnets from kimberlite and associated xenoliths. J. Geol.83, 589–609 (1975)
Dawson, J.B., Stephens, W.E.: Statistical classification of garnets from kimberlite and associated xenoliths; addendum. J. Geol.84, 495–496 (1976)
Dickey, J.S.: Eclogitic and other inclusions on the breccia member of the Deborah Volcanic Formation at Kakanui, New Zealand. Am. Mineral.53, 1304–1319 (1968)
Gurney, J.J., Fesq, H.W., Kable, E.J.D.: Clinopyroxene-ilmenite intergrowths from kimberlite: a re-appraisal. In: Lesotho kimberlites (P.H. Nixon, ed.), pp. 238–253. Maseru: Lesotho Dev. Corpn. 1973
Haggerty, S.E.: Spinels of unique composition associated with ilmenite reactions in the Liqhobong kimberlites. Lesotho. In: Lesotho kimberlites (P.H. Nixon, ed.), pp. 149–158. Maseru: Lesotho Dev. Corpn. 1973
Haggerty, S.E.: The chemistry and genesis of opaque minerals in kimberlites. Phys. Chem. Earth9, 295–307 (1975)
Hughes, G.W., Turner, C.C.: Upraised Pacific ocean floor, southern Malaita, Solomon Islands. Geol. Soc. Am. Bull.88, 412–424 (1977)
Nixon, P.H.: ed., Lesotho kimberlites. Maseru: Lesotho Nat. Develop. Corp. 1973
Nixon, P.H., Boyd, F.R.: Garnet bearing Iherzolites and discrete nodule suites from the Malaita alnöite, Solomon Islands, S.W. Pacific, and their bearing on oceanic mantle composition and geotherm. Ext. Abstr. 2nd Int. Conf. Kimberlites, unpaged (1977)
Rawlinson, P.J., Dawson, J.B.: A quench orthopyroxene-ilmenite xenolith from kimberlite-evidence for Ti-rich liquid in the upper mantle. Proc. 2nd Int. Conf. Kimberlites, Santa Fe (accepted for publication 1978)
Smith, J.V., Brennesholtz, R., Dawson, J.B.: Late-stage micas in kimberlite groundmass. Ext. Abstr. 2nd Int. Conf. Kimberlites, unpaged (1977)
Smith, J.V., Dawson, J.B.: Chemistry of Mg-rich micas from kimberlites and xenoliths, with implications for volatiles in upper mantle. Geol. Soc. Am., Abstr. Programs7, 1275–1276 (1975)
Smith, J.V., Hervig, R.L., Ackermand, D., Dawson, J.B.: K, Rb and Ba in micas from kimberlite and peridotitic xenoliths. Ext. Abstr. Proc. 2nd Int. Conf. kimberlites, unpaged (1977)
Stephens, W.S., Dawson, J.B.: Statistical comparison between pyroxenes from kimberlites and their associated xenoliths. J. Geol.85, 433–449 (1977)
Wagner, P.A.: The diamond fields of southern Africa. Johannesburg: Transvaal Leader 1914. Reprinted Cape Town: C. Struik (Pty) 1971
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Dawson, J.B., Delaney, J.S. & SmitH, J.V. Aspects of the mineralogy of alnöitic breccia, Malaita, Solomon Islands; comparison with continental kimberlites. Contr. Mineral. and Petrol. 67, 189–193 (1978). https://doi.org/10.1007/BF01046575
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DOI: https://doi.org/10.1007/BF01046575