scholarly journals Cenozoic structural evolution of the Catalina metamorphic core complex and reassembly of Laramide reverse faults, southeastern Arizona, USA

Geosphere ◽  
2021 ◽  
Author(s):  
Daniel A. Favorito ◽  
Eric Seedorff
Keyword(s):  
Structural Evolution ◽  
Normal Faults ◽  
Geologic Mapping ◽  
Core Complex ◽  
Cross Sectional ◽  
Detachment Faults ◽  
Metamorphic Core Complexes ◽  
Basement Rocks ◽  
Structural Levels ◽  
Metamorphic Core

This study investigates the Late Cretaceous through mid-Cenozoic struc­tural evolution of the Catalina core complex and adjacent areas by integrating new geologic mapping, structural analysis, and geochronologic data. Multiple generations of normal faults associated with mid-Cenozoic extensional deformation cut across older reverse faults that formed during the Laramide orogeny. A proposed stepwise, cross-sectional structural reconstruction of mid-Cenozoic extension satisfies surface geologic and reflection seismologic constraints, balances, and indicates that detachment faults played no role in the formation of the core complex and Laramide reverse faults represent major thick-skinned structures. The orientations of the oldest synextensional strata, pre-shortening nor­mal faults, and pre-Cenozoic strata unaffected by Laramide compression indicate that rocks across most of the study area were steeply tilted east since the mid-Cenozoic. Crosscutting relations between faults and synextensional strata reveal that sequential generations of primarily down-to-the-west, mid- Cenozoic normal faults produced the net eastward tilting of ~60°. Restorations of the balanced cross section demonstrate that Cenozoic normal faults were originally steeply dipping and resulted in an estimated 59 km or 120% extension across the study area. Representative segments of those gently dipping faults are exposed at shallow, intermediate (~5–10 km), and deep structural levels (~10–20 km), as distinguished by the nature of deformation in the exhumed footwall, and these segments all restore to high angles, which indicates that they were not listric. Offset on major normal faults does not exceed 11 km, as opposed to tens of kilometers of offset commonly ascribed to “detachment” faults in most interpretations of this and other Cordilleran metamorphic core complexes. Once mid-Cenozoic extension is restored, reverse faults with moderate to steep original dips bound basement-cored uplifts that exhibit significant involvement of basement rocks. Net vertical uplift from all reverse faults is estimated to be 9.4 km, and estimated total shortening was 12 km or 20%. This magnitude of uplift is consistent with the vast exposure of metamorphosed and foliated cover strata in the northeastern and eastern Santa Catalina and Rincon Mountains and with the distribution of subsequently dismembered mid-Cenozoic erosion surfaces along the San Pedro Valley. New and existing geochronologic data constrain the timing of offset on local reverse faults to ca. 75–54 Ma. The thick-skinned style of Laramide shortening in the area is consistent with the structure of surrounding locales. Because detachment faults do not appear to have resulted in the formation of the Catalina core complex, other extensional systems that have been interpreted within the context of detachments may require further structural analyses including identification of crosscutting relations between generations of normal faults and palinspastic reconstructions.

scholarly journals Tectonic denudation of a Late Cretaceous–Tertiary collisional belt: regionally symmetric cooling patterns and their relation to extensional faults in the Anatolide belt of western Turkey

2003 ◽  
Vol 140 (4) ◽  
pp. 421-441 ◽  
Author(s):  
UWE RING ◽  
CHRISTOPHER JOHNSON ◽  
RALF HETZEL ◽  
KLAUS GESSNER
Keyword(s):  
Late Cretaceous ◽  
Metamorphic Core Complex ◽  
Early Miocene ◽  
Second Phase ◽  
Late Oligocene ◽  
Core Complex ◽  
Cooling History ◽  
Western Turkey ◽  
Structural Levels ◽  
Metamorphic Core

Thermochronological data reveal that the Late Cretaceous–Tertiary nappe pile of the Anatolide belt of western Turkey displays a two-stage cooling history. Three crustal segments differing in structure and cooling history have been identified. The Central Menderes metamorphic core complex represents an ‘inner’ axial segment of the Anatolide belt and exposes the lowest structural levels of the nappe pile, whereas the two ‘outer’ submassifs, the Gördes submassif to the north and the Çine submassif to the south, represent higher levels of the nappe pile. A regionally significant phase of cooling in the Late Oligocene and Early Miocene affected the outer two submassifs and the upper structural levels of the Central Menderes metamorphic core complex. In the northern part of the Gördes submassif, cooling was related to top-to-the-NNE movement on the Simav detachment, as the apatite fission-track ages show a northward-younging trend in the direction of movement on this detachment. In the Çine submassif, relatively rapid cooling in Late Oligocene and Early Miocene times may have been related to top-to-the-S extensional reactivation of the basal thrust of the overlying Lycian nappes. The second phase of cooling in the Anatolide belt is related to Pliocene to Recent extension resulting in the formation of the Central Menderes metamorphic core complex in the inner part of the Anatolide belt. Core-complex development caused the formation of supra-detachment graben, which document the ongoing separation of the Central Menderes metamorphic core complex from the outer submassifs.

Interpretation of vintage 2D seismic reflection data along the Austrian-Hungarian border: Subsurface expression of the Rechnitz metamorphic core complex

2020 ◽  
Vol 8 (4) ◽  
pp. SQ73-SQ91 ◽  
Author(s):  
Gabor C. Tari ◽  
Ingrid Gjerazi ◽  
Bernhard Grasemann
Keyword(s):  
Seismic Data ◽  
Pannonian Basin ◽  
Metamorphic Core Complex ◽  
Border Zone ◽  
Data Sets ◽  
Core Complex ◽  
Seismic Reflection Data ◽  
Reflection Seismic ◽  
Detachment Faults ◽  
Metamorphic Core

In the border zone between Austria and Hungary, the Miocene extension of the Pannonian Basin was characterized by extreme, large-magnitude upper crustal extension accommodated along low-angle detachment faults. Although some of these prominent normal faults have already been described using 2D seismic data sets and well data on the Hungarian side, we offer the first systematic interpretation using the Austrian and Hungarian vintage seismic data sets acquired in the 1970s and 1980s. The refinement of the previously proposed metamorphic core complex (MCC) style, east-northeast–west-southwest-trending very high-strain extension provides a modern understanding of back-arc extension in this part of the Pannonian Basin system as the result of the collapse of the Alpine orogen. Although previous interpretations could not achieve the subsurface correlation of major structural elements across the border, we did systematically map these for the first time. Numerous exploration wells, drilled on both sides of the border, were integrated with reflection seismic data to differentiate between the lower versus upper plates of the major low-angle detachment faults, including the largest one responsible for the formation of the Rechnitz MCC. Based on our new interpretation, the regionally mapped Rechnitz detachment fault has an unexpectedly large subsurface extent, on the order of 1000 km2. Moreover, the unusually large number of industry 2D seismic profiles (approximately 50) used to map this and other prominent faults, in the Austrian and Hungarian sides, makes the Rechnitz MCC possibly the best constrained one in the world in terms of subsurface definition by reflection seismic data.

Structural evolution and related implications for uranium mineralization in the Patterson Lake corridor, southwestern Athabasca Basin, Saskatchewan, Canada

2020 ◽  
pp. geochem2020-030
Author(s):  
Dillon Johnstone ◽  
Kathryn Bethune ◽  
Colin Card ◽  
Victoria Tschirhart
Keyword(s):  
Structural Evolution ◽  
Uranium Mineralization ◽  
Ductile Deformation ◽  
Normal Faults ◽  
Uranium Deposits ◽  
Content Type ◽  
Athabasca Basin ◽  
Basement Rocks ◽  
Transfer Faults ◽  
Dextral Strike Slip

The Patterson Lake corridor is situated along the southwest margin of the Athabasca Basin and contains several basement-hosted uranium deposits and prospects. Drill core investigations during this study have determined that granite, granodiorite, mafic and alkali intrusive basement rocks are entrained in a deep-seated northeast-striking subvertical heterogeneous high-strain zone defined by anastomosing ductile to semi-brittle shears and brittle faults. The earliest phases of ductile deformation (D1/2), linked with Taltson (1.94–1.92 Ga) orogenesis, involved interference between early fold sets (F1/2) and development of an associated ductile transposition foliation (S1/2). During subsequent Snowbird (ca. 1.91–1.90 Ga) tectonism, this composite foliation was re-folded (D3) by northeast-trending buckle-style folds (F3), including a regional fold centered on the Clearwater aeromagnetic high. In continuum with D3, a network of dextral-reverse chloritic-graphitic shears, with C-S geometry, formed initially (D4a) and progressed to more discrete, spaced semi-brittle structures (D4b; ca. 1.900–1.819 Ga). Basin development (D5a; <ca. 1.819 Ga) was marked by a set of north-striking normal faults and related east- and northeast-striking transfer faults that accommodated subsidence. Primary uranium mineralization (D5b; ∼1.45 Ga) was facilitated by brittle reactivation of northeast-striking basement shears in response to west-southwest - east-northeast-directed compressional stress (σ1). Uraninite was emplaced along σ1-parallel extension fractures and dilational zones formed at linkages between northeast- and east-northeast-striking dextral strike-slip faults. Uranium remobilization (D5c) occurred after σ1 shifted to west-northwest – east-southeast, giving rise to regional east- and southeast-striking conjugate faults, along which mafic dykes (1.27 Ga and 1.16 Ga) intruded.Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathways

Permian rifting and detachment faults and their role in Alpine collisional tectonics

2021 ◽  
Author(s):  
Nikolaus Froitzheim ◽  
Linus Klug
Keyword(s):  
Normal Fault ◽  
Southern Alps ◽  
Detachment Fault ◽  
Metamorphic Core Complex ◽  
Rift System ◽  
Early Permian ◽  
Core Complex ◽  
Detachment Faults ◽  
The North ◽  
Metamorphic Core

&lt;p&gt;The Permian was a time of strong crustal extension in the area of the later-formed Alpine orogen. This involved extensional detachment faulting and the formation of metamorphic core complexes. We describe (1) an area in the Southern Alps (Valsassina, Orobic chain) where a metamorphic core complex and detachment fault have been preserved and only moderately overprinted by Alpine collisional shortening, and (2) an area in the Austroalpine (Schneeberg) where Alpine deformation and metamorphism are intense but a Permian low-angle normal fault is reconstructed from the present-day tectonometamorphic setting. In the Southern Alps case, the Grassi Detachment Fault represents a low-angle detachment capping a metamorphic core complex in the footwall which was affected by upward&amp;#8208;increasing, top&amp;#8208;to&amp;#8208;the&amp;#8208;southeast mylonitization. Two granitoid intrusions occur in the core complex, c. 289 Ma and c. 287 Ma, the older of which was syn-tectonic with respect to the extensional mylonites (Pohl, Froitzheim, et al., 2018, Tectonics). Consequently, detachment&amp;#8208;related mylonitic shearing took place during the Early Permian and ended at ~288 Ma, but kinematically coherent brittle faulting continued. Considering 30&amp;#176; anticlockwise rotation of the Southern Alps since Early Permian, the extension direction of the Grassi Detachment Fault was originally ~N&amp;#8208;S and the sense of transport top-South. In this area, there is no evidence of Permian strike-slip faulting but only of extension. In the Schneeberg area of the Austroalpine, a unit of Early Paleozoic metasediments with only Eoalpine (Cretaceous) garnet, the Schneeberg Complex, overlies units with two-phased (Variscan plus Eoalpine) garnet both to the North (&amp;#214;tztal Complex) and to the South (Texel Complex). The basal contact of the Schneeberg Complex was active as a north-directed thrust during the Eoalpine orogeny. It reactivated a pre-existing, post-Variscan but pre-Mesozoic, i.e. Permian low-angle normal fault. This normal fault had emplaced the Schneeberg Complex with only low Variscan metamorphism (no Variscan garnet) on an amphibolite-facies metamorphic Variscan basement. The original normal fault dipped south or southeast, like the Grassi detachment in the Southern Alps. As the most deeply subducted units of the Eoalpine orogen (e.g. Koralpe, Saualpe, Pohorje) are also the ones showing the strongest Permian rift-related magmatism, we hypothesize that the Eoalpine subduction was localized in a deep Permian rift system within continental crust.&lt;/p&gt;

P–T–t path for the lower plate of the Eocene Tatla Lake metamorphic core complex, southwestern Intermontane Belt, British Columbia

1992 ◽  
Vol 29 (5) ◽  
pp. 972-983 ◽  
Author(s):  
R. M. Friedman
Keyword(s):  
British Columbia ◽  
Metamorphic Core Complex ◽  
Crustal Thickening ◽  
Lower Plate ◽  
Normal Faults ◽  
Low Grade ◽  
Core Complex ◽  
T Path ◽  
C 50 ◽  
Metamorphic Core

The Tatla Lake metamorphic complex (TLMC) is a metamorphic core complex located along the western edge of the Intermontane Belt in southwestern interior British Columbia. Low- to moderate-angle normal faults separate lower plate greenschist- and amphibolite-grade, highly strained, commonly mylonitic rocks from unstrained to weakly deformed strata of the upper plate. The lower plate is divided into a core of granoblastic gneiss and migmatitic tonalite and an overlying, 1–2.5+ km thick mylonitic package called the ductilely sheared assemblage (DSA). Amphibolite-grade metamorphism of the gneissic core (Mc) largely accompanied the development and folding of gneissic layering (ca. 107–79 Ma). Eocene (ca. 55–47 Ma) fabric and mineral assemblages in the DSA (Ms) obscure any earlier history. Three metamorphic zones are observed within southern DSA metapelites with increasing structural depth: chlorite–biotite, garnet–staurolite, and garnet–staurolite–kyanite–sillimanite. The middle zone is about 300 m thick; the latter zone is now about 4 km below low-grade upper plate rocks, indicating late- or post-Ds metamorphic omission. DSA P–T conditions are calculated with the garnet–biotite thermometer and garnet–Al2SiO5–quartz–plagioclase (GASP) and total Al in hornblende barometers. Southern DSA metapelites record Eocene Ms conditions of 480–619 °C (± 50 °C), generally increasing with depth. One sample gave a calculated P–T of 0.72 ± 0.15 GPa and 500 ± 50 °C. P–T data from this area suggest that up to 10 km of structural section may be missing. Zoned garnet (pre-Ds) core to rim GASP pressures of 0.70–0.36 ± 0.15 GPa, for an outcrop-sized pelitic xenolith within a Late Cretaceous tonalitic body (U–Pb: 71 Ma) in the northwestern DSA, record its ascent during pluton emplacement and subsequent Eocene tectonic uplift. A total Al in hornblende crystallization pressure of 0.54 ± 0.1 GPa was calculated for the surrounding body. Biotite and hornblende K–Ar dates of 53.4–45.6 Ma for DSA and gneissic core rocks record cooling of the lower plate through the 530–280 °C (± 40 °C) interval. Mc metamorphism in the gneissic core is thought to have developed in response to crustal thickening and compression, beneath a regional mid-Cretaceous thrust belt. Characteristics of Eocene Ms metamorphism in the DSA, such as truncated and thinned metamorphic zones, are consistent with development during extensional tectonic exhumation of the lower plate.

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