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CARMIGNANI L., FRANCESCHELLI M., GHEZZO C., MEMMI I., PERTUSATI P.C. RICCI C.A. (1981)- Some PT time path recorded in the Sardinia metamorphic basement. Terra Abstract EUG I, Strasbourg
No full text
The Terra Nova Intrusive Complex, Victoria Land, Antarctica (with 1:50,000 geopetrographic map)
No full textDuring the early Palaeozoic Ross Orogeny, the Wilson Terrane of northern
Victoria Land was extensively intruded by felsic and mafic magmas. Plutons resulting from
this igneous activity include an intrusive complex that crops out along the coast of northern
Victoria Land at Terra Nova Bay which has been the subject of a detailed field, petrographic,
petrologic, geochemical, isotopic and geochronologic work. This paper and the attached map
summarize the results of this work on the composite Terra Nova Intrusive Complex. The
complex evolved by multiple emplacement pulses that can be recognised by differences in
internal structures and intrusive relationships. Generally, each major magmatic episode is
characterized by mafic as well as felsic rocks, which commonly show textures indicative of
intermingling and mixing. The different units and their internal variations (mafic,
intermediate and felsic bodies) were identified and distinguished from each other in the field
and then validated with petrographic-petrologic studies, thus yielding a geopetrographic
map. Field data indicate strong variations in the stress regime during emplacement of the
various magmatic units, with decreasing intensity of deformation and shallowing of
emplacement level with time
Oxygen isotope evidence for crustal assimilation and magma mixing in the Granite Harbour Intrusives, Northern Victoria Land, Antarctica
No full textThe stable isotope composition (O,H) of whole-rock and mineral separates of Cambrian-Ordovician gabbros, diorites, granodiorites and granites forming the Mt. Abbott composite intrusions (Northern Victoria Land, Antarctica) was measured to constrain the origin and evolution of the magmas postdating the Ross Orogen. The delta(18)O values of olivine gabbros plot in the field of slightly evolved mantle-derived melts (delta(18)O(WR) = 6.8-7.4parts per thousand). The O-isotope character of the mantle source inferred from the 6180 values of cumulous olivine in gabbros (5.7-6.8parts per thousand) is enriched in O-18 compared to modem arc-related magmas. Geochemical data and concurrent high 6180 values, and initial strontium (Sr-87/Sr-86=0.7060) and neodymium (Nd-143/Nd-144=0.5122) isotope ratios indicate that the olivine gabbros formed by crustal contamination of a primary calc-alkaline basaltic melt. The diorites have high 6180 values, among the highest ever measured for dioritic rocks (8.7-10.3parts per thousand), and Sr-isotope ratios that partially overlap with the adjacent and mingled felsic lithologies (0.708-0.710). The diorites have pyroxene with high, nearly constant (delta(18)O values (8.2-8.6parts per thousand) that are independent from the silica content of the rocks; thus, they did not increase in response of the chemical evolution of the rocks. The diorites originated from the same primary calc-alkaline basalt experiencing different amounts of crustal contamination, and underwent different degrees of mixing with the adjacent granites, producing granodioritic facies and quartz/feldspar xenocrystic diorites. The delta(18)O, Sr-87/Sr-86 and Nd-143/Nd-144 compositions of the granites and granodiorites overlap (10.8-12.1parts per thousand, 0.7096-0.7108, 0.5119-0.5120). They are distinct from the values of the mafic rocks and indicate that gabbros and granites were not cogenetic. The granites are a separate melt component likely derived from nonmodal partial melting of fertile meta-igneous protoliths. (C) 2002 Elsevier Science B.V. All rights reserved
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