The evolution of a mid-crustal thermal aureole at Cerro Toro, Sierra de Famatina, NW Argentina

被引:27
作者
Alasino, P. H. [1 ,2 ]
Casquet, C. [3 ]
Larrovere, M. A. [1 ,2 ]
Pankhurst, R. J. [4 ]
Galindo, C. [3 ]
Dahlquist, J. A. [5 ]
Baldo, E. G. [5 ]
Rapela, C. W. [6 ]
机构
[1] Consejo Nacl Invest Cient & Tecn, Ctr Reg Invest Cient & Transferencia Tecnol La Ri, RA-5301 Anillaco, La Rioja, Argentina
[2] UNLaR, INGeReN, CENIIT, RA-5300 La Rioja, Argentina
[3] Univ Complutense, CSIC, Dpto Petr & Geoquim, IGEO, E-28040 Madrid, Spain
[4] British Geol Survey, Nottingham NG12 5GG, England
[5] UNC, CONICET, CICTERRA, Cordoba, Argentina
[6] Natl Univ La Plata, CONICET, CIG, RA-1900 La Plata, Buenos Aires, Argentina
关键词
I-type magmatism; Middle crust emplacement; Anatexis; Hybridization; Sierra de Famatina; GRANITIC MAGMAS; METASEDIMENTARY ROCKS; CONTACT-METAMORPHISM; PHASE-EQUILIBRIA; PELITIC SYSTEM; VALLE FERTIL; ORIGIN; BEARING; DISEQUILIBRIUM; ORDOVICIAN;
D O I
10.1016/j.lithos.2013.12.006
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
A more than 12 km wide sheeted tonalite complex in western Sierra de Famatina, NW Argentina, was emplaced at middle crust levels (ca. 5 kbar), coeval with regional metamorphism during an early phase of the Ordovician Famatinian orogeny (ca. 480 Ma). Advective heat from the tonalite complex caused a rise in the host regional temperatures (<= 700 degrees C) by a maximum of ca. 100 degrees C, developing an aureole (similar to 3 km wide) parallel to the igneous contact. This was accompanied by significant melting (ca. 40%) of the host rocks that hybridized to a variable extent with the tonalitic magmas. Three metamorphic zones were distinguished in a cross-section through the aureole: (1) an external zone consisting of metatexitic gneisses, amphibolites and minor tonalites, (2) an intermediate zone formed by screens of highly melted gneisses, amphibolites and metagabbros lying between tonalite and newly formed leucogranitoid and hybrid rock sheets, and (3) an internal zone formed almost exclusively of massive tonalite and minor hybrid rocks. Incongruent melting of biotite in gneisses of the intermediate zone produced peritectic cordierite and garnet. Hybrids resulting from variable mixing of anatectic granitoids and tonalite magma developed in the innermost part of the aureole at 750-800 degrees C. Increased water activity within this zone eventually promoted increased melting of plagioclase + quartz in the gneisses. Leucogranitoid magmas formed in part by extraction from the hybrid magmas led to heterogeneity of the Sr-isotope composition. The Cerro Toro contact aureole shows that assimilation of metasedimentary rocks through partial melting can play an important role during emplacement of tonalitic magmas at mid-crustal levels. (C) 2013 Elsevier B.V. All rights reserved.
引用
收藏
页码:154 / 172
页数:19
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