Deformation of chlorite-mica aggregates in cleaved psammitic and pelitic rocks from Islesboro, Maine, U.S.A.

Document Type


Publication Date



Chlorite-white mica aggregates are large porphyroblasts found in weakly metamorphosed and deformed pelitic and psammitic rocks throughout the world. They are usually considered to originate either as detrital white mica layers surrounded by crystallized chlorite or as synkinematic porphyroblasts. In chlorite-muscovite aggregates observed at Islesboro, the chlorite layers were found to represent prekinematic porphyroblasts that have been strongly deformed and rotated during cleavage development. The muscovite layers in the aggregates formed by crystallization along split and dislocated (001) surfaces in the chlorite, or by alteration within intensely deformed sections of chlorite grains, such as kink-bands. © 1986.

Publication Title

Journal of Structural Geology