Rare structure in Chapter 6: Various Structures

LARROVERE, MARIANO A.

Atlas of Structural Geology

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015; p. 137 - 137

FIGURE 6.24 Rare structure named here piggyback porphyroclasts?, in granite mylonite to protomylonite. The structure shows two large porphyroclasts of K-feldspar occurring together in the central part of the photo and displaying strongly curved contacts due to crystal-plastic deformation. Notice the conjugate set of microfractures on the lower part of the contact zone inside the left porphyroclast. Subvertical curved contact between both porphyroclasts and linked conjugate microfractures suggest compression in the horizontal direction. Section oblique to the lineation and normal to the foliation. Width of view 206 mm. Location: Sierra de Velasco, La Rioja Province, NW Argentina. GPS point (WGS84): S 28°36′34.5″-W 67°10′41.1″ Rock type: Mylonite to protomylonite. Formation name: Ortogneiss Antinaco (TIPA Shear Zone) Age (relative): Post- Lower Ordovician / Pre- Carboniferous Facies/grade: medium grade.