The Paleoproterozoic Pr & oslash;ven Igneous Complex (PIC) of the Rinkian Orogen in central West Greenland comprises a suite of arc-related charnockite plutons, extending over an area of at least 7200 km2. The PIC was emplaced into paragneisses of the Karrat Group during a series of magmatic events between c. 1900 and 1850 Ma. Magmatism was accompanied by high-grade metamorphism and deformation, culminating in granulite facies peak conditions and partial melting at c. 1820 Ma. To unravel the conditions of charnockite formation and granulite facies metamorphism, a detailed petrographic study was carried out on samples from the PIC and the surrounding paragneisses. The rock types studied include i) charnockites from the massive PIC, ii) charnockites and migmatites from the layered lower PIC, iii) migmatites from the surrounding paragneisses, and iv) igneous enclaves from the lower PIC. Charnockites from the massive PIC generally show a magmatic, porphyritic texture and only minor macro-textural evidence of deformation. The lower PIC and paragneisses are both migmatized and exhibit extensive recrystallization with a solid-state crystal-plastic fabric. Igneous enclaves are found within the lower PIC and show an equigranular, igneous texture. Based on the dominant igneous texture it is interpreted that the massive PIC crystallized from a dry magma and was not significantly overprinted during peak metamorphism. Phase equilibrium modelling, Hb-Pl thermometry and Al-in-hornblende barometry constrain the PIC to have been emplaced at 680-795 degrees C and 4.2-5.4 kbar. By contrast, the lower PIC and paragneiss samples record granulite facies peak conditions of 785-805 degrees C and 3.4-4.0 kbar, suggesting that both charnockite magmatism and metamorphism took place at relatively shallow crustal levels. Our results are consistent with the P-T conditions recorded by the 1890-1880 Ma Qikiqtarjuaq Plutonic Suite, an arc-type charnockite intrusion on Baffin Island, Canada. A correlation between the tectonothermal events on Baffin Island and in the Rinkian Orogen is proposed, therefore relating the intrusion of the PIC to the collision of the Meta Incognita microcontinent and the Rae Craton.

The "Rinkian belt" of West Greenland is a metamorphic terrain of Paleopro-terozoic age comprising: (1) the north Rinkian fold-thrust belt (FTB)-a pro-or fore -arc domain, highly deformed and metamorphosed with widespread anatexis; (2) the PrOven Igneous Complex-a magmatic arc characterized by hypersthene granitic rocks ("charnockites"); (3) the south Rinkian FTB-an inverted back -arc basin; and 4) a continental margin or foreland. Recognition of this tectonic architecture demonstrates that the "Rinkian" is a bona fide oro-genic belt-the Rinkian orogen-and not simply the imbricated lower plate of the Nagssugtoqidian orogen. Arc plutons of the PrOven Igneous Complex were emplaced into the Karrat Group at ca. 1.90- 1.85 Ga, dividing a back -arc basin into pro-and retro -arc domains. In the former-the north Rinkian FTB-WSW-directed thrusting (deformation events D1-D2) and high -grade metamorphism were taking place by ca. 1.875 Ga and were continuous through ca. 1.850 Ga with a peak temperature at ca. 1.830 Ma accompanied by anatexis in the Karrat Group and lower units of the PrOven Igneous Complex. In the retro -arc domain-the south Rinkian FTB-thrusting to the E (D1) began at ca. 1.870 Ma followed by thrusting to the W (D2) at ca. 1.830- 1.820 Ga with displacement focused into a major high-temperature ductile shear zone which carried the PrOven Igneous Complex in the hanging wall of an Andean -type, crustal-scale, "pop -up" structure. High-temperature deformation continued during D3 when the pro -arc, arc, and retro -arc domains were shortened by bivergent detach-ment folding and thrusting at ca. 1.820- 1.810 Ga.

In central West Greenland, early Palaeoproterozoic siliciclastic and carbonate sequences of the Karrat Group (shelf sequences of the Rae craton margin) were deposited in sedimentary basins controlled by NW- and SW-trending linked extensional fault systems. The shelf basins were later filled and overtopped by turbidite systems filling a foredeep advancing ahead of a thrust system - the Karrat Fjord thrust system - that propagated west to east. Deformation culminated in emplacement of basement-cored nappes, progressive deformation and high-grade metamorphism at c. 1.87 Ga. Reactivation of lower plate growth faults formed dome- and basin-like folds and related thrusts that refolded the structure of the Karrat Fjord thrust system and inverted the shelf basins. The southern Karrat Fjord thrust system was reworked in a belt of intense ductile NW-directed thrusting - the Nunaarsussuaq thrust system-formed at c. 1.84 Ga at the northern limit of the Nagssugtoqidian orogen. Kinematics of these events are at odds with the consensus view that the Rinkian fold-thrust belt is a northward extension of the Nagssugtoqidian orogen resulting from north-south convergence between the Rae and North Atlantic cratons. Application of structural restoration techniques to basin analysis of Palaeoproterozoic rocks has potential to provide new insights into Proterozoic orogenic processes worldwide.

Cu-Au-Mo porphyry-type and Cu skarn-type mineralization in the Bingham mining district of Utah are temporally and spatially related to a suite of monzonite and quartz monzonite porphyry intrusions comprising the Bingham complex. Structural control on mineralization at the Bingham Canyon mine has been described at the scale of individual large-scale folds and fracture sets but no integrated pattern for the synmineralization deformation structures has emerged from earlier research. In the work reported here we have investigated hitherto largely unrecognized components of deformation (translations, rotations, and strains) associated with emplacement of many cubic kilometers of granitic rocks in the intrusions of the Bingham district. We have used both the local three-dimensional static mine model and the regional context in digital kinematic two- and three-dimensional forward and reverse modeling to identify a geometrically valid and admissible fault framework for the Bingham district and a kinematic solution for this framework through time. The results indicate that porphyry intrusions and associated mineralization were emplaced during reactivation of a basement-dictated linked system comprising two sets of northwest- and (north)-northeast-trending strike-slip faults. Both sets operated as transfer faults during extensional collapse of the Sevier orogen in the Eocene. Each fault set is characterized by overstep geometries with relay ramps breached by faults (re)activated in extension. Strike-slip was accompanied by progressive dilation of the extensional faults in fault oversteps to permit emplacement of composite stocklike (low aspect ratio) intrusions. The kinematic fault framework identified provides a new structural context for porphyry- and skarn-type mineralization at the Bingham Canyon mine, with potential for linking mineralizing fluid flow to three-dimensional structure and the development of that structure through time.

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.

[1] New paleomagnetic data from the Coastal Cordillera-Precordillera boundary area of northern Chile, east of Copiapo, between 26 degrees 00'S and 28 degrees 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 degrees 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 similar to 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.

The Candelaria Fe oxide Cu-Au ore deposit lies within the thermal aureole of the Lower Cretaceous magmatic arc plutonic suite in the Candelaria-Punta del Cobre district, Atacama region, northern Chile (27 degrees 30' S). Economic mineralization is present within a synplutonic ductile shear zone (Candelaria shear zone) containing foliated and potassically altered volcanic and volcaniclastic rocks of the Punta del Cobre Formation. In tire Candelaria shear zone, there was a complex interplay in space and time between ductile and brittle deformation during mineralization. At high structural levels brittle, moderately to steeply dipping extensional faults curve downward into gently dipping ductilely deformed rocks in the shear zone. Textural and structural characteristics of the ore and the deformed rocks indicate that the dilation of the sulfide-bearing vein systems occurred at tire same time as ductile deformation and implies that ductile-brittle cycling occurred in a cooling hydrothermal system in the thermal aureole of the are plutonic rocks.7The La Brea and the San Gregorio plutonic complexes are exposed in the plutonic arc immediately adjacent to the Candelaria orebody. The intrusions are interpreted to be flat-lying, tabular bodies emplaced by roof uplift-floor depression mechanisms during regional extensional deformation. An Ar-40/Ar-39 age of 119.6 +/- 1.2 Ma and five K-Ar ages between 123 and 117 Ma were obtained for the La Brea pluton, and an Ar-40/Ar-39 age of 111.5 +/- 0.4 Ma was obtained for the San Gregorio plutonic complex. Ar-40/Ar-39 ages of 111.0 +/- 1.4 and 110.7 +/- 1.6 Ma obtained from syntectonic biotite from the Candelaria shear zone are interpreted to be the age of the mineralization. These are indistinguishable from the age of the San Gregorio plutonic complex, and therefore heat from this pluton could have promoted ductile deformation during emplacement of the orebody. This result, together with known isotopic similarities between Candelaria ore and the plutonic rocks, implies that the San Gregorio plutonic complex was the most probable source of the mineralizing fluids at Candelaria, although the critical intrusive unit may not be exposed. The ore deposit is located where a roof-uplift fold in the sidewall of the San Gregorio plutonic complex provided a dilatational site which may have drawn hydrothermal fluids out of the adjacent fractionating magmas into a structural trap in the Punta del Cobre Formation below the carbonate rocks of the Chanarcillo Group.

We have reanalyzed the pattern of paleomagnetically detected rotations in the central Andes (the central Andean rotation pattern) in order to investigate the temporal and spatial distributions of rotations. The dominant pattern of rotation is well known with counterclockwise rotations in the northern Andes (clockwise in the southern Andes) linked to Neogene orogenesis and shortening. However, much of the rotation in the forearc of northern Chile (23-30 degrees S) is distinctly anomalous because of markedly high rotations that appear to predate rotations observed elsewhere in the central Andes. We argue that the data define a domain located in the forearc of northern Chile marked by major (> 25 degrees) clockwise crustal rotations related to late Paleocene-early Eocene highly oblique convergence. This rather diffuse and cryptic deformation style accommodated strong shortening perpendicular to the Andean margin by vertical axis rotations rather than by conventional fold-thrust belts or transpressional fault systems.

Subhorizontal attachment zones provide coupling between lithospheric layers in orogenic belts. A mid-crustal attachment zone is exposed in the Palaeoproterozoic Ketilidian orogen, south Greenland, which formed as a result of north-directed oblique convergence at a cordilleran-type margin. Rifting (c. 2.1 Ga) and compressional deformation and magmatism (> 1850 Ma) on the continental margin was followed by an extended sinistral transpression from 1850 to 1730 Ma now separated into three episodes or peaks of activity. The first episode was focused on the back-arc region and was followed by the main arc construction phase during which transpression was partitioned into strike-slip and contraction components. Despite the longevity of this active margin system, individual tectonic events took place rapidly, e.g. development of fore-arc D-1-D-3 and accompanying high-temperature, low-pressure metamorphism took place over c. 12 Ma. We explain the fore-arc and batholith evolution by the upward migration of an underlying attachment Structure through the upper crustal partitioned blocks. This migration may be attributed to an increase in the geothermal gradient accompanied by, or followed by, exhumation of the mid-crust. The partially molten. hence weak, attachment zone solidified and strengthened during cooling before emplacement of the post-orogenic rapakivi suite during the third distinct phase of mild sinistral transpression.

Continental tectonics, and the formation of mountain belts, do not adhere to the plate tectonic paradigm (Molnar 1988). Mountain belts at plate boundaries are areas of diffuse deformation in which geologists have recognized that not only are the plates not rigid (Gordon 1998), but parts of the lithosphere (e.g. upper crust) are moving laterally with respect to other parts (e.g. lower crust), such as in thrust belts (Bally et al. 1966). An exciting development in tectonics is the detailed investigation of the behaviour of continental crust during orogenesis. In particular, the role of coupling (attachment) or decoupling (detachment) of the lithospheric layers during continental deformation has significant implications for all aspects of modern and ancient tectonics. The recognition of regional detachments or décollements, an idea developed in foreland fold and thrust belts, was the first major contribution to our understanding of the vertical stratification in orogenic belts. Elucidation of the structure of foreland fold and thrust belts in the external parts of orogens by the development of the techniques of balanced cross-section construction (Price 1981, 1986) and deep seismic reflection profiling (e.g. Mueller et al. 1980) showed that foreland thrust systems are typically think-skinned and bounded at depth by a basal detachment, décollement or sole thrust. Shortening in the external parts of cordilleran and collisional orogens was taken up by folding and thrusting above a basement which remained essentially undeformed and part of the foreland (e.g. Bally et al. 1966). Balanced cross-section techniques were developed and refined in the Alberta

Cretaceous rocks on the continental margin of northern Chile record a complex geodynamic evolution. Cycles of transtensional and transpressional deformation and of extrusive and intrusive magmatism are linked to the development of crustal-scale lineaments. The Landsat Thematic Mapper is used here as a tool to define these structural features. Geocorrected data were digitally enhanced and lineaments plotted directly from a hard copy image, thereby excluding artificial or non-geological features that might degrade the subsequent structural analysis. The lineaments were then digitized and analysed using a Weighted Moving Average (WMA) technique to suppress noise and to enhance azimuthal variation. Statistical analysis of the data reveals three lineament populations. The first is a set of NNE-trending lineaments that belong to the margin-parallel, sinistral Atacama Fault System. The second is a series of NW-trending lineaments with a similar orientation to large-scale structures identified across the South American continental plate. The third is a widely spaced set of NE-trending lineaments. The key result of this study is that lineaments identified from remotely sensed data may have orientation patterns that differ considerably from those identified by traditional geological mapping and that full structural analysis of structurally complex crustal regions will likely be incomplete without a comprehensive analysis of remotely sensed data. Although the NW-trending structures are numerically dominant on the Landsat TM image, they are seldom recorded at map scale and are under-represented on published geological maps. Of the 275 faults marked on the published geological map sheets, 89 are N to NNE-trending and only 88 are NW-trending. By contrast, of 841 lineaments identified from the satellite image, 455 are NW-trending and 178 are N- to NNE-trending. The lack of prior recognition of the NW-trending structures means that their importance has been underestimated in reconstructions of the geodynamic evolution of the region. In addition, as major ore deposits in the region are frequently located at intersections between two fracture systems, the recognition here of the NW-trending set of structures should illuminate future mineral exploration programmes.