Chita Pluton, NW Argentina: Constraints on host rock displacement during pluton emplacement
View looking east-northeast of the roof of Chita granite pluton, summit is 5140 m; lowest exposures occur below 3400 m, indicating over 1.7 km of vertical relief within the pluton.
Geologic map of the Chita pluton, San Juan Province, NW Argentina. Trajectories of bedding are shown as well as recent, NW-trending strike-slip fault that cuts the pluton. Note location of cross section A-A'. View looking southeast, down the long axis of the exposed Chita pluton into the deeply incised Chita canyon. Roof and wall exposures are shown with white and black arrows.
Geologic cross section of the Chita pluton. All relationships shown on the cross section can be observed along the walls of Chita canyon and are projected onto the cross section plane.The pluton truncates the host rock structure and stratigraphy along a discordant contact.
View from road looking obliquely up towards wall contact of pluton shown in lower half of image D to the left. Note the large xenolith (long dimension ~80 m; noted with white arrow). Black lines within pink granite are mafic dikes, white lines within gray host rocks are granitic dikes.
Shallowly dipping bedding truncated at roof-wall corner along the S-SW margin of the pluton.
View of roof-wall transition. Road in foreground is at 3400 m while the roof crops out above 4500 m, indicating over 1100 m of exposure at this locality. Note jagged wall contact & local presence of host rock xenoliths incorporated in pluton.
Interpretive diagram drawn to scale depicting three time steps in the construction of the Chita pluton and displacement of the host rocks. Diagonal-ruled area represents zone of ductile deformation that should accomodate floor subsidence. Although the early mechanisms of chamber construction are unconstrained, both stoping and floor-subsidence are permitted. Magnitude of surace doming is represnted by changes in elevation of the pluton roof contact between the last two time steps, and by displacment of the upper cross-section boundary in the upper time step.

For more information see: Yoshinobu, A.S., Fowler, T.K., Paterson, S.R., Llambias, E., Sato, A., and Tickyj, Hugo, 2003, A view from the roof: magmatic stoping in the shallow crust, Chita pluton, Argentina. Journal of Structural Geology, v. 25, p. 1037-1048.