Two-mica Monzogranite Research Articles

Use of nonparametric ranking statistics to characterize magmatic and post-magmatic processes in the eastern South Mountain Batholith, Nova Scotia, Canada

The South Mountain Batholith is a large, post-tectonic, peraluminous, granitoid complex consisting of many coalesced plutons. Compositions range from biotite granodiorite, through two-mica monzogranite, to muscovite leucogranite. Application of the non-parametric Spearman rank correlation coefficient (SRCC) statistic to major- and trace-element chemical data from one large pluton (the Halifax Pluton), and to two different groups of much smaller leucogranitoid bodies, shows strongly different correlation coefficients in the three groups. The Halifax Pluton shows strong SRCCs between compatible elements (Ba, Sr, Zr, Sc, V, La) and weak SRCCs for the incompatible elements (Rb, Ta, Nb, Li, F, Sn). The leucogranites generally show correlations opposite to the Halifax Pluton, and also show some strong correlations between elements that were poorly correlated in it (Na, K, Li, P). Non-geological controls (such as closure, dissimilar compositional ranges, dissimilar groupings, and differing analytical precisions) cannot account for the observed differences between the magnitudes and signs of the correlation coefficients in the three groups. On the other hand, geological controls (principally magmatic vs. hydrothermal) do explain most of the differences in the correlation coefficients, and the transition between magmatic and hydrothermal control is apparent. Spearman rank correlation coefficients can be used with compositional data drawn from populations with non-normal distributions: to provide a comprehensive and rapid, nongraphical assessment of inter-element correlations; to quantify these inter-element relationships; and to both identify processes, and to gauge their relative contributions to the observed compositions.

Etude comparative des granites hyperalumineux de la Nouvelle-Ecosse (zone du Méguma) et du massif central marocain dans le cadre du magmatisme acide associé aux orogenèses paléozoïques

The Paleozoic granites of the Meguma zone, which is a suspect terrane in the eastern Appalachians, belong to the South Mountain batholith, one of the largest in northeastern America. Like most of the Hercynian granites of Morocco, particularly those of the Central Massif, they are peraluminous and were emplaced in the terranes that were deformed and metamorphosed in epizonal conditions during an orogeny. The granitic rocks of the Meguma are very similar to those of the Moroccan Central Massif, and are composed of earlier biotite granodiorites and later two-mica monzogranites. Both the granodiorites and the monzogranites are abundantly cut by aplites, pegmatites and porphyry dikes. The geochemical and metallogenic evolution of the Meguma granites is also very comparable to that of the Moroccan granites. However, the age and the scale of ‘granization’ in the Meguma zone are not the same as in the Hercynian Morocco, and this demands a great deal of caution in interpreting the petrochemical resemblances between the granitic rocks of the two regions in favour of a Moroccan origin of the Meguma.