Petrogenesis of Upper Paleozoic post-collisional peraluminous leucogranites, Sierra de Ancasti, northwest Argentina

The Santa Rosa and Sauce Guacho plutons are two post-collisional peraluminous Late Devonian to Early Carboniferous leucogranites that intruded the banded schists of the Ancasti Formation. The leucogranites are composed of microcline phenocrysts along with quartz, plagioclase, muscovite, biotite, ilmenite, tourmaline, apatite, monazite and zircon. Their geochemical composition is consistent with S-type granites and mineralogically they belong to MPG granites (muscovite-peraluminous granites). It is proposed that granite magma generation was related to shear zones that concentrated fluids in the metasedimentary crust during a collision or transcurrent tectonics. U-Pb analyses on monazite gave an age of 369.8 +/- 5.3 Ma, while Sm/Nd isotopic data yield epsilon(Nd(t)) values of -5.3 for Sauce Guacho and -5.7 for Santa Rosa indicating crustal provenance. Nd model ages between 1,544 and 1,571 Ma are within the range of magmatic rocks from the Lower Ordovician Famatinian Arc in the Central Sierras Pampeanas.

A criterion for unitary similarity of upper triangular matrices in general position

Each square complex matrix is unitarily similar to an upper triangular matrix with diagonal entries in any prescribed order. Let A = [a(ij)] and B = [b(ij)] be upper triangular n x n matrices that are not similar to direct sums of square matrices of smaller sizes, or are in general position and have the same main diagonal. We prove that A and B are unitarily similar if and only if parallel to h(A(k))parallel to = parallel to h(B(k))parallel to for all h is an element of C vertical bar x vertical bar and k = 1, ..., n, where A(k) := [a(ij)](i.j=1)(k) and B(k) := [b(ij)](i.j=1)(k) are the leading principal k x k submatrices of A and B, and parallel to . parallel to is the Frobenius norm. (C) 2011 Elsevier Inc. All rights reserved.