Computer Science
Scientific paper
Mar 1987
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1987gecoa..51..421c&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 51, Issue 3, pp.421-438
Computer Science
1
Scientific paper
The 2.6 Ga Lac du Bonnet batholith of ~ 1000 km 2 surface exposure is emplaced along a longlived regional fault. The batholith was generated by successive intrusions that have undergone different degrees of modification by internal processes or by tectonic effects: (i) minor early porphyritic hornblendebiotite granodiorite; (ii) extensive silicic leucogranite (with interior barren and exterior Be, Nb > Ta, Y, REE, F, Zr, Th, U, Ti-bearing pegmatites); (iii) dominant biotite granite with xenoliths of (basement?) tonalite, containing extensive K-feldspar porphyroblastesis; (iv) minor undeformed but porphyroblastic late biotite granodiorite. The chemistry of the two granodiorites is closely related to that of the biotite granite but the geochemical features of the leucogranite are markedly different. Isotopic constraints ( 18 O of +8.1, R Sr i of 0.7003) and K 2 O content suggest LIL-depleted tonalite with <25% greenstone-belt metasediments as the probable source of biotite granite. Very modest negative Eu anomalies and low HREE of the granite are compatible with a tonalitic protolith. Melting of short-lived felsic volcanics would also satisfy all constraints but encounters a potential mass balance problem. Extensive K-feldspar porphyroblastesis had no significant effect on bulk compositions, alkali-feldspar-bound elements or Rb-Sr isotope systematics but it disturbed magmatic oxygen to +6.7-+11.0 and remarkably depleted P, Zr, Hf, Th and all REE except Eu. The highly evolved leucogranite could have been affected by liquid fractionation, was depleted in volatile components and rare lithophile elements extracted into its pegmatite aureole, and its disturbed Rb-Sr isotope systematics could have resulted from pervasive shearing and recrystallization. The overall geochemical features of the leucogranite ( 18 0 + 7.9, R Sr i ~ 0.7000, high Fe / Mg , LREE > HREE with very prominent negative Eu anomaly, and Nb > Ta, Y, F signature of derived pegmatites) rank it with A-type granites.
Černý Petr
Fryer Brian J.
Longstaffe Frederick J.
Tammemagi Hans Y.
No associations
LandOfFree
The Archean Lac du Bonnet batholith, Manitoba: Igneous history, metamorphic effects, and fluid overprinting does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Archean Lac du Bonnet batholith, Manitoba: Igneous history, metamorphic effects, and fluid overprinting, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Archean Lac du Bonnet batholith, Manitoba: Igneous history, metamorphic effects, and fluid overprinting will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1455534