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Extensive tracts of magmatic arc plutonic suites in the Mesozoic Coastal Cordillera of northern Chile imply that large volumes of granitic to dioritic magmas were transferred from a lower crustal source to the upper crust. Space for single intrusions was created by interaction of vertical pluton growth and dip-slip reactivation of arc-parallel faults during episodic emplacement of subhorizontal, compositionally distinct magma pulses. Cross-sectional pluton shapes are broadly tabular in geometry and were controlled by differential subsidence of the pluton floors during fault reactivation and incremental assembly of subhorizontal sheets. Equal amounts of floor subsidence of the fault footwall and hanging wall during magma accommodation led to symmetrical intrusions, whereas differential subsidence caused plutons to grow asymmetrically. Strongly asymmetrical plutons resulted when only the hanging wall was reactivated to accommodate floor subsidence. Late, post-intrusion contractional deformation resulted in open folding of some tabular plutonic units and local inversion of bounding faults, which has modified but not obscured the original syn-emplacement geometry and fault kinematics.

New paleomagnetic data from the Coastal Cordillera‐Precordillera boundary area of northern Chile, east of Copiapó, between 26°00′S and 28°00′S are reported. Early Cretaceous to earliest Paleocene volcanics and sediments are nearly completely remagnetized, the remagnetization typically being carried by both magnetite and hematite. In a small minority of sites a pretilting remanence is retained, however, both pretilting and posttilting remanences yield similar directions. These remanences plus primary remanences from Paleocene intrusions indicate a significant >35° rotation of the whole area, in agreement with previous results from the region. The data suggest that the whole of this part of the Andean fore arc has undergone a substantial, regionally coherent, clockwise rotation. This rotation, it is argued, is in response to rapid and highly oblique Nazca–South American plate convergence in the period ∼60–45 Ma prior to later Incaic deformation in the east of the study area. In the east, heterogeneous rotations associated with the Domeyko Fault System are interpreted as being superimposed on this regional rotation resulting in a highly variable and localized pattern of rotations in the vicinity of the main structures comprising the fault system itself.

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