The geology, geochemistry and structure of the Mooshla intrusion, Bousquet Mining Centre, Quebec.

Abstract

The Mooshla intrusion is an elliptical body, 4.0 x 1.5 km and is hosted by the Blake River Group, a fault bounded sequence of bi-modal volcanic and volcaniclastic rocks. The intrusion is calc-alkaline in affinity and comprises four distinct units; (1) cumulate gabbros, (2) quartz diorites, (3) tonalites, and (4) leucotonalites. The cumulate gabbros are composed of two textural facies; (1) mesocumulates and (2) a layered sequence. Textural and geochemical evidence suggests that the leucotonalite is the hydrothermally altered and sheared equivalent of the tonalite. The intrusion records four generations of structures; D$\sb1$, D$\sb2$, D$\sb3$, and D$\sb4$. D$\sb1$ produced an E-W striking foliation, S$\sb1$, that dips moderately to the south and is localized to the core of the intrusion. D$\sb2$ represents a period of subhorizontal N-S compression and is the principal deformation event. It is responsible for an $\approx$E-W trending, regionally penetrative foliation, S$\sb2$, that dips steeply to the south and onto which most geological objects are flattened. Both D$\sb3$ and D$\sb4$ are reflected by predominantly brittle structures related to dominantly E-W directed horizontal shortening. The Mooshla intrusion can be subdivided into three structural domains defined by which foliation they contain and the nature and frequency of the high strain zones that they host. (Abstract shortened by UMI.)