scholarly journals Interplay of Cretaceous transpressional deformation and continental arc magmatism in a long-lived crustal boundary, central Fiordland, New Zealand

Geosphere ◽  
2020 ◽  
Vol 16 (5) ◽  
pp. 1225-1248
Author(s):  
Hannah J. Blatchford ◽  
Keith A. Klepeis ◽  
Joshua J. Schwartz ◽  
Richard Jongens ◽  
Rose E. Turnbull ◽  
...  
Keyword(s):  
New Zealand ◽  
Thermal Structure ◽  
Shear Zones ◽  
Arc Magmatism ◽  
Magmatic Arc ◽  
Continental Arcs ◽  
Metasedimentary Rocks ◽  
Spatio Temporal ◽  
Continental Magmatic Arc ◽  
Lower Crustal

Abstract Recovering the time-evolving relationship between arc magmatism and deformation, and the influence of anisotropies (inherited foliations, crustal-scale features, and thermal gradients), is critical for interpreting the location, timing, and geometry of transpressional structures in continental arcs. We investigated these themes of magma-deformation interactions and preexisting anisotropies within a middle- and lower-crustal section of Cretaceous arc crust coinciding with a Paleozoic boundary in central Fiordland, New Zealand. We present new structural mapping and results of Zr-in-titanite thermometry and U-Pb zircon and titanite geochronology from an Early Cretaceous batholith and its host rock. The data reveal how the expression of transpression in the middle and lower crust of a continental magmatic arc evolved during emplacement and crystallization of the ∼2300 km2 lower-crustal Western Fiordland Orthogneiss (WFO) batholith. Two structures within Fiordland’s architecture of transpressional shear zones are identified. The gently dipping Misty shear zone records syn-magmatic oblique-sinistral thrust motion between ca. 123 and ca. 118 Ma, along the lower-crustal WFO Misty Pluton margin. The subhorizontal South Adams Burn thrust records mid-crustal arc-normal shortening between ca. 114 and ca. 111 Ma. Both structures are localized within and reactivate a recently described >10 km-wide Paleozoic crustal boundary, and show that deformation migrated upwards between ca. 118 and ca. 114 Ma. WFO emplacement and crystallization (mainly 118–115 Ma) coincided with elevated (>750 °C) middle- and lower-crustal Zr-in-titanite temperatures and the onset of mid-crustal cooling at 5.9 ± 2.0 °C Ma−1 between ca. 118 and ca. 95 Ma. We suggest that reduced strength contrasts across lower-crustal pluton margins during crystallization caused deformation to migrate upwards into thermally weakened rocks of the mid-crust. The migration was accompanied by partitioning of deformation into domains of arc-normal shortening in Paleozoic metasedimentary rocks and domains that combined shortening and strike-slip deformation in crustal-scale subvertical, transpressional shear zones previously documented in Fiordland. U-Pb titanite dates indicate Carboniferous–Cretaceous (re)crystallization, consistent with reactivation of the inherited boundary. Our results show that spatio-temporal patterns of transpression are influenced by magma emplacement and crystallization and by the thermal structure of a reactivated boundary.

Geochronological and kinematic constraints on crustal shortening and escape in a two-sided oblique-slip collisional and magmatic orogen, Paleoproterozoic Taltson magmatic zone, northeastern Alberta

2000 ◽  
Vol 37 (11) ◽  
pp. 1549-1573 ◽  
Author(s):  
Michael R McDonough ◽  
Vicki J McNicoll ◽  
Ernst M Schetselaar ◽  
Timothy W Grover
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Remotely Sensed Data ◽  
Kinematic Data ◽  
Magmatic Arc ◽  
Magmatic Rocks ◽  
Ductile Shear Zones ◽  
Continental Magmatic Arc ◽  
Northeastern Alberta ◽  
Lower Crustal

The southern Taltson magmatic zone (south of 60°N) is a composite continental magmatic arc and collisional orogen resulting from the convergence of the Buffalo Head terrane with the Archean Churchill craton. Taltson basement (ca. 3.2–3.0 Ga and 2.4–2.14 Ga) and Rutledge River supracrustal gneisses (2.13–2.09 Ga) were intruded by voluminous I- and S-type magmatic rocks between 1.99 and 1.92 Ga. Taltson magmatic zone was deformed by three ductile shear zones: Leland Lakes, Charles Lake, and Andrew Lake, exhibiting both strike- and dip-lineated mylonitic domains. Kinematic data for shear zones are reported at microscopic, mesoscopic, and macroscopic (remotely sensed data) scale. We present field and U–Pb isotopic data (zircon and monazite) for magmatic and metamorphic rocks that constrain the timing of granulite to upper amphibolite-grade shearing in the Leland Lakes and Charles Lake (formerly Allan) shear zones to ca. 1938–1934 Ma. Foreland (easterly) vergent thrusting on the Andrew Lake shear zone is ca. 1932 Ma. Taltson shear zones were overprinted by widespread amphibolite- to greenschist-grade shearing, which is constrained by published 40Ar–39Ar and K–Ar dates on hornblende and muscovite to between ca. 1900 and 1800 Ma. We propose a crustal architecture, resembling a crustal-scale asymmetric flower structure, in which the Charles Lakes shear zone formed the fundamental shear zone of a middle to lower crustal sinistral transpression system that accommodated southward escape of crust in the upper plate of an oblique continental subduction–collision zone, with shortening partitioned into synchronous outwardly vergent thrust systems to the east and west of the main shear zone.

scholarly journals Tectonothermal ordovician evolution of the western margin of the Famatinian magmatic arc: metamorphism of the mafic and ultramafic rocks of Sierra de la Huerta -Las Imanas (Pampean Ranges, Argentina)

2010 ◽  
Vol 33 (2) ◽  
pp. 277
Author(s):  
Juan A. Murra ◽  
Edgardo G. Baldo
Keyword(s):  
Ultramafic Rocks ◽  
Compositional Variation ◽  
Sierras Pampeanas ◽  
Middle Ordovician ◽  
Magmatic Arc ◽  
Metasedimentary Rocks ◽  
Erosion Rates ◽  
Continental Magmatic Arc ◽  
Uplift And Erosion ◽  
East West

An important magmatic and tectonometamorphic activity of Early and Middle Ordovician age is registered in the pre-Andean basement of the Sierras Pampeanas of Argentina. These were linked to the development of a continental magmatic arc during the Famatinian Orogeny, resulting from the approach and attachment of an alleged exotic terrane (the Precordillera Terrane), to the south western Gondwana's margin (present coordinates). A suit of meta-mafic and ultramafic rocks are exposed in the Sierras de La Huerta and Las Imanas, at the western limit of the famatinian orogen. Metaperidotites (Ol-Opx-Cpx-Am-Spl), coronitic metapyroxenites (Opx-Cpx-Spl-Am-Pl), metaquartz-norites (Opx-Pl-Am-Qtz-Bt±Grt) and metadiorites (Pl-Am-Qtz-Bt-Ep) are associated with metasedimentary rocks (marbles, gneisses and migmatites with Sil+Kfs+Grt) that reached the peak and post-peak conditions of metamorphism at middle Ordovician time. The meta-mafic rocks record a first high-grade metamorphic event (M1-730ºC and 8.4±0.5 kbar) and a second lower pressure event (M2, 720ºC and 4.5 kbar) with Cum+Hbl+Mag in a coronitic assemblage. The meta-ultramafic rocks also record the two metamorphic events, but only for the second one it was possible to calculate the P-T conditions. At latitude 32º30'S, the Famatinian magmatic arc shows a systematic compositional variation normal to its trend, i.e. in an east-west direction, which could be related to present erosion levels. In this context, the mafic and ultramafic units of Sierras de La Huerta and Las Imanas, probably represent the deepest levels of the magmatic arc which is consistent with the position that they show marginal to the orogenic belt, i.e., where the uplift and erosion rates were larger.

scholarly journals Detrital zircon record of Phanerozoic magmatism in the southern Central Andes

Geosphere ◽  
2021 ◽  
Author(s):  
T.N. Capaldi ◽  
N.R. McKenzie ◽  
B.K. Horton ◽  
C. Mackaman-Lofland ◽  
C.L. Colleps ◽  
...  
Keyword(s):  
South America ◽  
Detrital Zircon ◽  
Temporal Distribution ◽  
Arc Magmatism ◽  
Clear Trend ◽  
Isotopic Signatures ◽  
Magmatic Arc ◽  
Rough Approximation ◽  
Southern Central ◽  
Continental Magmatic Arc

The spatial and temporal distribution of arc magmatism and associated isotopic variations provide insights into the Phanerozoic history of the western margin of South America during major shifts in Andean and pre-Andean plate interactions. We integrated detrital zircon U-Th-Pb and Hf isotopic results across continental magmatic arc systems of Chile and western Argentina (28°S–33°S) with igneous bedrock geochronologic and zircon Hf isotope results to define isotopic signatures linked to changes in continental margin processes. Key tectonic phases included: Paleozoic terrane accretion and Carboniferous subduction initiation during Gondwanide orogenesis, Permian–Triassic extensional collapse, Jurassic–Paleogene continental arc magmatism, and Neogene flat slab subduction during Andean shortening. The ~550 m.y. record of magmatic activity records spatial trends in magma composition associated with terrane boundaries. East of 69°W, radiogenic isotopic signatures indicate reworked continental lithosphere with enriched (evolved) εHf values and low (<0.65) zircon Th/U ratios during phases of early Paleozoic and Miocene shortening and lithospheric thickening. In contrast, the magmatic record west of 69°W displays depleted (juvenile) εHf values and high (>0.7) zircon Th/U values consistent with increased asthenospheric contributions during lithospheric thinning. Spatial constraints on Mesozoic to Cenozoic arc width provide a rough approximation of relative subduction angle, such that an increase in arc width reflects shallower slab dip. Comparisons among slab dip calculations with time-averaged εHf and Th/U zircon results exhibit a clear trend of decreasing (enriched) magma compositions with increasing arc width and decreasing slab dip. Collectively, these data sets demonstrate the influence of subduction angle on the position of upper-plate magmatism (including inboard arc advance and outboard arc retreat), changes in isotopic signatures, and overall composition of crustal and mantle material along the western edge of South America.

scholarly journals Temporal and spatial variations in magmatism and transpression in a Cretaceous arc, Median Batholith, Fiordland, New Zealand

Lithosphere ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 652-682 ◽  
Author(s):  
Luisa F. Buriticá ◽  
Joshua J. Schwartz ◽  
Keith A. Klepeis ◽  
Elena A. Miranda ◽  
Andy J. Tulloch ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
New Zealand ◽  
Shear Zone ◽  
High Strain ◽  
Shear Zones ◽  
Separation Point ◽  
Ca 125 ◽  
Arc Magmatism ◽  
Spatial And Temporal Patterns ◽  
Middle Crust

Abstract We investigated the interplay between deformation and pluton emplacement with the goal of providing insights into the role of transpression and arc magmatism in forming and modifying continental arc crust. We present 39 new laser-ablation–split-stream–inductively coupled plasma–mass spectrometry (LASS-ICP-MS) and secondary ion mass spectrometry (SIMS) 206Pb/238U zircon and titanite dates, together with titanite geochemistry and temperatures from the lower and middle crust of the Mesozoic Median Batholith, New Zealand, to (1) constrain the timing of Cretaceous arc magmatism in the Separation Point Suite, (2) document the timing of titanite growth in low- and high-strain deformational fabrics, and (3) link spatial and temporal patterns of lithospheric-scale transpressional shear zone development to the Cretaceous arc flare-up event. Our zircon results reveal that Separation Point Suite plutonism lasted from ca. 129 Ma to ca. 110 Ma in the middle crust of eastern and central Fiordland. Deformation during this time was focused into a 20-km-wide, arc-parallel zone of deformation that includes previously unreported segments of a complex shear zone that we term the Grebe shear zone. Early deformation in the Grebe shear zone involved development of low-strain fabrics with shallowly plunging mineral stretching lineations from ca. 129 to 125 Ma. Titanites in these rocks are euhedral, are generally aligned with weak subsolidus fabrics, and give rock-average temperatures ranging from 675 °C to 700 °C. We interpret them as relict magmatic titanites that grew prior to low-strain fabric development. In contrast, deformation from ca. 125 to 116 Ma involved movement along subvertical, mylonitic shear zones with moderately to steeply plunging mineral stretching lineations. Titanites in these shear zones are anhedral grains/aggregates that are aligned within mylonitic fabrics and have rock-average temperatures ranging from ∼610 °C to 700 °C. These titanites are most consistent with (re)crystallization in response to deformation and/or metamorphic reactions during amphibolite-facies metamorphism. At the orogen scale, spatial and temporal patterns indicate that the Separation Point Suite flare-up commenced during low-strain deformation in the middle crust (ca. 129–125 Ma) and peaked during high-strain, transpressional deformation (ca. 125–116 Ma), during which time the magmatic arc axis widened to 70 km or more. We suggest that transpressional deformation during the arc flare-up event was an important process in linking melt storage regions and controlling the distribution and geometry of plutons at mid-crustal levels.

scholarly journals Explanatory notes to the Geological Map of Greenland, 1:100 000, Ussuit 67 V.2 Nord

2007 ◽  
pp. 1-40 ◽  
Author(s):  
Jeroen A.M. Van Gool ◽  
Mogens Marker
Keyword(s):  
Shear Zones ◽  
Hydrothermal Activity ◽  
Easy Access ◽  
Dimension Stone ◽  
Magmatic Arc ◽  
Metasedimentary Rocks ◽  
The North ◽  
Rock Types ◽  
Tectonic Contact ◽  
Intrusive Suite

The Ussuit map area is situated around the inner Nassuttooq (Nordre Strømfjord) in central West Greenland, in the core of the Palaeoproterozoic Nagssugtoqidian orogen. The orogen largely consists of reworked Archaean gneisses, as well as Palaeoproterozoic ortho- and paragneisses in its central part. Easy access through the branched fjord system and good exposures along its coastlines, combined with less intense reworking compared to neighbouring areas to the west and south, have made the Ussuit map area the most intensely studied and best known part of the orogen. The most recent research and mapping projects were organised by the Danish Lithosphere Centre (1994–1999) and the Geological Survey of Denmark and Greenland (2000–2001). The predominant rocks are late Archaean tonalitic and granodioritic orthogneisses, intruded by postkinematic granites. Archaean supracrustal rocks are predominantly of mafic composition, but only few have been recognised. Palaeoproterozoic rocks occur as tectonic sheets (the Ussuit unit) which are always in tectonic contact with the Archaean orthogneisses. The most abundant Palaeoproterozoic rock types are biotite schist and biotite-bearing paragneiss, besides orthogneiss of the Arfersiorfik intrusive suite. The latter rocks are mainly deformed quartz diorites intrusive into the metasedimentary rocks and interpreted as remnants of a magmatic arc above a subduction zone. The Ussuit unit also includes amphibolite, marble and calc-silicate rocks, and lenses of ultrabasic rocks. Small bodies of younger syn- and post-tectonic granites occur throughout the map area. The interleaved Palaeoproterozoic and Archaean rocks form a major anticlinal fold structure between two crustal-scale shear zones, the Nordre Strømfjord shear zone in the north and the Nordre Isortoq steep belt in the south. These shear zones formed during the latest ductiledeformation event (D4), following ductile thrusting (D1) and kilometre-scale folding (D2 and D3). The deformation and high grade metamorphism are the result of collision of two Archaean blocks at c. 1850 Ma, with a presumed strongly deformed suture rooted in the southern Ussuit area. No economically feasible mineral occurrences have been discovered to date within the Ussuit map area. Minor sulphide mineralisation related to hydrothermal activity occurs in faults and shear zones, and minor stratabound iron formations have been observed. The most promising industrial mineral deposits are minor diopside occurrences and potential dimension stone in migmatised orthogneiss.

Giant granulite terranes of northeastern Superior Province: the Ashuanipi complex and Minto block

1992 ◽  
Vol 29 (10) ◽  
pp. 2287-2308 ◽  
Author(s):  
J. A. Percival ◽  
J. K. Mortensen ◽  
R. A. Stern ◽  
K. D. Card ◽  
N. J. Bégin
Keyword(s):  
Large Scale ◽  
Accretionary Prism ◽  
Granulite Facies ◽  
Superior Province ◽  
Arc Magmatism ◽  
High Grade ◽  
Block Rotation ◽  
Magmatic Arc ◽  
Metasedimentary Rocks ◽  
Lithological Character

The Ashuanipi complex and Minto block of the Superior Province are large regions that have been classified as "high-grade gneiss" terranes on the basis of the presence of orthopyroxene-bearing units. Like the granite–greenstone and metasedimentary subprovinces of the southern Superior Province, the two terranes consist predominantly of intrusive rocks, but are distinguished by their primary magmatic orthopyroxene. Both "high-grade" and "gneiss" are misnomers because granulite-facies gneisses are only sparingly present and the regions consist dominantly of massive, unmetamorphosed plutonic rock.The Ashuanipi complex consists of a deformed, metamorphosed package of metasedimentary rocks and primitive, early tonalite cut by widespread orthopyroxene ± garnet granodiorite (diatexite), as well as plutons of tonalite, granite, and syenite. Based on its lithological and chronological similarity and on-strike position, the complex appears to be the continuation of metasedimentary subprovinces such as the Quetico. Its evolution involved deposition of immature greywacke in an accretionary prism, early arc (tonalitic) magmatism and deformation, followed by widespread intracrustal magmatism in the period 2700–2670 Ma. Both metamorphic and igneous rocks record equilibration under granulite-facies conditions (700–835 °C; 0.35–0.65 GPa; [Formula: see text] ~0.3) and indicate exposure levels of ~20 km.The Minto block at the latitude of Leaf River consists of several north-northwest-trending domains of similar scale and diversity to the east-trending subprovinces of the southern Superior Province. The central Goudalie domain is dominantly amphibolite-facies tonalitic rocks including some with ages >3 Ga, with small belts of volcanic and sedimentary origin. Lake Minto domain contains poorly preserved supracrustal remnants in a plutonic complex comprising hornblende granodiorite, clinopyroxene ± orthopyroxene granodiorite, orthopyroxene–biotite diatexite, and granite. The hornblende granodiorite suite constitutes most of the Utsalik and Tikkerutuk domains and is thought to represent continental arc magmatism. On the basis of their distinct aeromagnetic and lithological character, two additional domains are evident north of the Leaf River area, the Inukjuak domain in the west and the Douglas Harbour domain in the east.The northerly grain of the Minto block appears to have been established in situ with respect to the easterly belts of the southern Superior Province (i.e., no large-scale block rotation) during the same interval of time (3.0–2.7 Ga). Modification of the tectonic framework for the Superior Province is required to explain Minto arc magmatism. In the interval ~2730–2690 Ma ago, a continental magmatic arc built the Berens River and Bienville subprovinces and Minto block on the southern and eastern edges, respectively, of a northern protocratonic foundation. In the same period, primitive volcanic arcs and accretionary prisms developed outboard on oceanic crust and were accreted to form a southern tectonic regime.

STRAIN ACCOMMODATION AND 3D KINEMATICS OF TRANSPRESSIONAL FLOW WITHIN THE LOWER CRUST OF A CRETACEOUS MAGMATIC ARC IN FIORDLAND NEW ZEALAND

2018 ◽  
Author(s):  
Griffin A. Moyer ◽  
◽  
Jesse Lee ◽  
Christopher Eddy ◽  
Elena A. Miranda ◽  
...  
Keyword(s):  
New Zealand ◽  
Lower Crust ◽  
3D Kinematics ◽  
Magmatic Arc
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