Mylonites from the Kumaun Lesser Himalaya
Bhattacharya, A. R.; Agarwal, K. K.
Neues Jahrbuch für Mineralogie - Abhandlungen Band 152 Heft 1 (1985), p. 65 - 77
20 references
published: Jun 21, 1985
ArtNo. ESP154015201004, Price: 29.00 €
Abstract
A well defined mylonite zone at the southern boundary of a large (Almora) crystalline unit of the Lesser Himalaya has been recognised here. A number of mylonite types, including a new one “quasi mylonite” has been identified. The mylonites show three types of structural fabric: (i) a prominently developed mylonitic foliation (Sa fabric) corresponding to the XY plane of the small-scale strain ellipsoid, (ii) a non-penetrative fabric (Sb) in the form of fractures in the feldspar porphyroclasts, possibly indicating a departure from essentially an initial ductile to essentially brittle state of deformation, and (iii) a micro-structural feature (Sc) possibly developed under conditions of heterogenous deformation. According to their deformation intensity, the various mylonite types and the included porphyroclasts are typically distributed in a haphazard manner. The mylonite zone thus exhibits an inhomogenous deformation pattern, broadly controlled by mineralogical heterogeneities in the mylonitic rock types, especially by the differences in the ductility of quartz and feldspar.
Keywords
Mylonite • fabric • Kumaun Lesser Himalaya • India