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Disharmonic Folds in Biotite-Psammite, Tangtse, Karakoram Shear Zone, Ladakh, NW India


Disharmonic Folds

Roberto Weinberg, Monash University, Australia



Copyright 2004-2011 by Roberto Weinberg. All rights reserved. Unlimited permission to copy or use is hereby granted for non-profit driven enterprise, subject to inclusion of this copyright notice and acknowledgment of the source URL:


I would very much appreciate an email stating how this material will be used: Roberto Weinberg, Monash University, Australia. Thanks, RW.


DISCLAIMER. The material on this website has not undergone the scrutiny of Monash University and does not conform to its corporate web design. It is entirely based on a free-spritied, curiosity-driven research effort by the author, and therefore in no way expresses the official position of the University.


leucogranite dyke in disharmonic fold, 3828 Figure 1. Deformed leucogranite dykes displaying disharmonic, irregular and ptygmatic folds in a biotite psammite in the Karakoram Shear Zone, Ladakh, NW India. Melting of the psammite took place at approximately 17Ma.


From McLellan,  1984, Geol. Mag., 121, p. 339: "in partially molten systems contaning more than 30% melt the classical theories of fold formation are inapplicable; the folds produces are of the 'viscous fold' type.  Their geometries are impredictable and may mimic structures due to refolding..."


Ptygmatic folds, 3825
Figure 1B.
Ptygmatic folds, 3823
Figure 1C. Ptygmatic folds at the hinge zone of B.
Folded and boudinaged dykes, 3829
Figure 1D. Folded and boudinaged dykes.
pegmatite in boudin neck, 3826
Figure 1E. Detail of D showing pegmatite in bouding neck.


Leucogranite dykes displaying disharmonic (ptygmatic), irregular folds in a biotite psammite in the Karakoram Shear Zone, Ladakh, NW India. Melting of the psammite took place at approximately 17Ma. THE FOLLOWING PHOTOS ARE ALL FROM THE SAME REGION OF ABOUT 100 X 100 M, WHERE LEUCOGRANITE AND PEGMATITE DYKES INTRUDE AND ARE DEFORMED WITHIN A BIOTITE PSAMMITE LAYER.
Ptygmatic folds, 3818
Figure 2.
Ptygmatic folds, 3820
Figure 3. Ptygmatic folds at the hinge zone of Fig. 2.
leucogranite folds, 3803
Figure 4. Discontinuous leucogranite folds.
leucogranite folds 3805crop
Figure 5. Leucogranite folds. Hinge zones broken up by the surrounding psammite. Discontinuous limbs.
rootless fold 3807
Figure 6. Irregular, rootless folds
rootless fold 3808
Figure 7.
rootless fold 3810

rootless fold 3816
Figure 9. Irregular, rootless folds.


Figure 8. Irregular, rootless folds.
folded and boudinaged dyke 3817
Figure 10A. Folded and boudinaged leucogranite dyke
folded and boudinaged dyke 3815
Figure 10B. Detail of A
rootless folds, 3822
Figure 11A.
rootless folds, 3821
Figure 11B.