Permian Intrusive Rocks Research Articles

Permian tectonic evolution and continental accretion in the eastern Central Asian Orogenic Belt: A perspective from the intrusive rocks

The tectonic evolution and history of continental accretion of the eastern Central Asian Orogenic Belt (CAOB) are not yet fully understood. In this study, we investigate Permian intrusive rocks from the Jiamusi Block of the eastern CAOB to constrain the tectonic evolution and continental accretion of this region during the late-stage evolution of the Paleo-Asian Ocean. Our new data show that Early Permian gabbro-diorites were derived from the partial melting of depleted mantle metasomatized by oceanic-slab-released fluids. Middle Permian adakitic granites have low Na2O and MgO and high K2O contents, indicating a thickened-lower-crust source. Late Permian S-type granites were derived from the partial melting of continental crust. A compilation of the available geochronological data for Permian intrusive rocks (including adakitic and A-, S-, and I-type granites and mafic rocks) from the eastern CAOB reveals that the A-type granites formed mainly during the Early–Middle Permian, S-type and adakitic granites mostly during the Middle–Late Permian, and I-type granites and mantle-derived mafic rocks throughout the Permian. The A-type granites, which are proposed to have been sourced from thinned continental crust, indicate an extensional setting in the eastern CAOB during the Early Permian. The Middle–Late Permian adakitic granites imply a thickened continental crust, which indicates a compressional setting. Therefore, the eastern CAOB underwent a transition from extension to compression during the Middle Permian, which was probably triggered by the late-stage subduction of Paleo-Asian oceanic crust. Considering the petrogenesis of the intrusive rocks and inferred regional tectonic evolution of the eastern CAOB, we propose that vertical underplating of mantle- and oceanic-slab-derived magmas contributed the materials for continental crust accretion.

Petrogenesis of Early Permian Intrusive Rocks from Southeastern Inner Mongolia, China: Constraints on the Tectonic Framework of the Southeastern Central Asian Orogenic Belt

AbstractThe late Paleozoic tectonic framework of the southeastern Central Asian Orogenic Belt is key to restricting the accretion orogeny between the Siberia Craton and the North China Craton. To clarify the framework, petrogenesis of early Permian intrusive rocks from southeastern Inner Mongolia was studied. Zircon U‐Pb dating for bojite and syenogranite from Ar‐Horqin indicate that they were emplaced at 288–285 Ma. Geochemical data reveal that the bojite is highly magnesian and low‐K to middle‐K calc‐alkaline, with E‐MORB‐type REE and IAB‐like trace element patterns. The syenogranite is a middle‐K calc‐alkaline fractionated A‐type granite and shows oceanic‐arc‐like trace element patterns, with depleted Sr‐Nd‐Hf isotopes, (87Sr/86Sr)I = 0.7032–0.7042, εNd(t) = +4.0 to +6.6 and zircon εHf(t) = +11.14 to +14.99. This suggests that the bojite was derived from lithospheric mantle metasomatized by subducted slab melt, while the syenogranite originated from very juvenile arc‐related lower crust. Usng data from coeval magmatic rocks from Linxi–Ar‐Horqin, the Ar‐Horqin intra‐oceanic arc was reconstructed, i.e., initial transition in 290–280 Ma and mature after 278 Ma. Combined with regional geological and geophysical materials in southeastern Inner Mongolia, an early Permian tectonic framework as ‘one narrow ocean basin of the PAO’, ‘two continental marginal arcs on its northern and southern’ and ‘one intra‐oceanic arc in its southern’ is proposed.

Final-Stage Magmatic Record of Paleo-Asian Oceanic Subduction? Insights from Late Permian to Early Triassic Intrusive Rocks in the Yanbian Area, Easternmost Central Asian Orogenic Belt

This paper reports new zircon LA–ICP–MS U–Pb and Hf isotope data, and whole-rock major and trace element data for Late Permian to Early Triassic intrusive rocks in the Yanbian area, NE China. These data provide new insights into the timing of the final subduction of the Paleo-Asian Ocean beneath the North China Craton. The zircon U–Pb age data indicate that a suite of Late Permian to Early Triassic intrusive rocks related to subduction is present within the Yanbian area. The Late Permian intrusive rocks consist of diorites while the Early Triassic granites and hornblende gabbros constitute a geochemically bimodal igneous rock association. Furthermore, the Early Triassic granites show the geochemical characteristics of shoshonitic rocks. All the rocks are characterized by enrichment in LILEs and LREEs, and depletion in HREEs and HFSEs, suggesting they formed in a subduction setting. Zircons from the Early Triassic gabbros have εHf(t) values and TDM2 ages of +7.6 to +10.7 and 735–1022 Ma, respectively, suggesting that they formed from a primary magma generated by the partial melting of lithospheric mantle material that had been previously modified by subduction-related fluids. The Late Permian diorites have εHf(t) values and TDM2 ages of +0.5 to +9.5 and 853 to 1669 Ma, respectively, while they have high contents of Al2O3, Fe2O3, and low contents of SiO2, Cr, and Ni, indicating Late Permian diorites should derive from the mantle and are influenced by some crustal material. Early Triassic granitic rocks have a wide range of εHf(t) values and TDM2 ages of −4.8 to +9.4 and 852 to 2136 Ma, respectively. Their zircons imply that the Early Triassic granites could be mainly derived from partial melting of the crust, with minor contribution of the crustal material of an ancient crust. The Early Triassic bimodal intrusive rocks in Yanbian area, combined with the regional geologic information; therefore, record a final post-subduction extensional environment due to the break-off of the previously subducted slab.

Late Paleozoic igneous rocks in the Xing’an Massif and its amalgamation with the Songnen Massif, NE China

We present new zircon U–Pb–Hf isotopic and whole-rock geochemical data for late Paleozoic igneous rocks from the Xing’an Massif, Northeast China, to further our understanding of the amalgamation of the Xing’an and Songnen massifs. Zircon laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) U–Pb ages indicate that late Paleozoic magmatism occurred in the Xing’an Massif over three stages: during the early Carboniferous (359–352 Ma), early late Carboniferous (327–320 Ma), and late Carboniferous–early Permian (307–295 Ma). The early Carboniferous igneous rocks are mainly quartz diorite, granodiorite, monzogranite, syenogranite, and rhyolite, and formed in an active continental margin setting related to the westward subduction of the Heihe–Nenjiang oceanic plate. The early late Carboniferous monzogranites are medium-K calc-alkaline I-type granitoids, with zircon εHf(t) values of +5.6 to +13.0 and TDM2 ages of 973–502 Ma, suggesting that the primary magma was derived from the partial melting of newly-accreted crust. The early late Carboniferous igneous rocks formed in collisional setting, marking the amalgamation of the Xing’an and Songnen massifs. The late Carboniferous–early Permian intrusive rocks are dominated by diorite, monzogranite, syenogranite, alkali-feldspar granite, and granite porphyry. The large volume of alkali feldspar granites and A-type granites suggested that they formed in a post-collisional extensional environment.

Geochronological and geochemical data for Late Palaeozoic–Mesozoic intrusive rocks in the Wenkutu area, northeastern China: New constraints on the tectonic evolution of the Great Xing'an Range

The occurrence of igneous rocks within the Wenkutu area, northeastern China, allows the Late Palaeozoic–Mesozoic geodynamic setting of the Great Xing'an Range to be investigated. Here, we present petrographic, geochemical, and geochronological data for intrusive rocks within the Wenkutu area. Zircon U–Pb geochronology reveals that magmatism occurred during the Early Carboniferous (ca. 334 Ma), Early Permian (ca. 296 Ma), Middle Jurassic (ca. 170 Ma), and Early Cretaceous (ca. 130 Ma). The Early Carboniferous intrusive rocks are intermediate–mafic, metaluminous, and medium‐K calc‐alkaline, have low SiO2 (49.57–55.00 wt.%) and high MgO (3.00–4.77 wt.%), Cr (average 60.64 ppm), and Ni (average 24.73 ppm) contents, and high Mg# (average 45.1) values. These features, together with their significant depletion in Nb, Ta, and Ti, and their enriched Sr–Nd isotopic compositions, suggest that these Early Carboniferous rocks were derived from the mantle and subsequently contaminated by crustal material. The Early Permian, Middle Jurassic, and Early Cretaceous intrusive rocks are intermediate–acidic, peraluminous, and high‐K calc‐alkaline, enriched in light rare‐earth elements, Rb, Th, U, K, P, and Hf, relatively depleted in heavy rare‐earth elements, Nb, Ta, and Ti, and have Eu/Eu* values of 0.05–0.86. These features indicate that the rocks were derived by the partial melting of lower crust. Our results, together with those of previous studies, suggest that the Late Palaeozoic intrusive rocks formed during collision between the Songnen and Xing'an massifs. The Early Permian intrusive rocks formed during the transition from an orogenic to a non‐orogenic environment. The Middle Jurassic intrusive rocks formed during the closure of the Mongol–Okhotsk Ocean (MOO) and were emplaced along the western part of the suture zone. The Early Cretaceous intrusive rocks formed during non‐orogenic extension and were related to the final closure of the MOO or to rollback of the Palaeo‐Pacific Plate.

Geochronology, geochemistry, and tectonic significance of Permian intrusive rocks from the Shaolanghe region, northern margin of the North China Craton

In situ zircon U–Pb ages and Hf isotopic data, whole‐rock major and trace element contents, and Sr–Nd isotopic compositions are reported for Permian intrusive rocks at Shaolanghe in Eastern Inner Mongolia in order to explore the magmatic origin and tectonic significance of these rocks for the evolution of the northern margin of the North China Craton. Three intrusive rocks, quartz diorite, Xishuiquan granite, and Xinglong granite, yield zircon U–Pb ages of 285.9 ± 3.1, 274.2 ± 2.9, and 260.0 ± 8.4 Ma, respectively. The quartz diorite and Xishuiquan granite belong to the high‐K calc‐alkaline series, enriched in large ion lithophile elements (e.g., Rb) and depleted in high field strength elements (e.g., Nb and Ti). They are defined as I‐type granites. The quartz diorite has initial 87Sr/86Sr ratios of 0.7049–0.7051, εNd(t) values of −10.0 to −11.4, and εHf(t) values of −15.2 to −9.9. The εHf(t) values of the Xishuiquan granite (−4.8 to 4.0) vary in discrete segments, whereas the εNd(t) values (−12.9 to −13.3) are consistent with those of the quartz diorites (−10.0 to −11.4). A magma mixing model is proposed for the formation of the quartz diorites of the Shaolanghe region, and the Xishuiquan granite was likely derived from partial melting of the Paleoproterozoic crust with involvement of mantle components. Geochemical analyses show that the tectonic setting of the northern margin of the North China Craton during the late Palaeozoic was an Andes‐type active continental margin associated with subduction of the Paleo‐Asian Ocean plate.

U–Pb ages of zircons from Mesozoic intrusive rocks in the Yanbian area, Jilin Province, NE China: Transition of the Paleo-Asian oceanic regime to the circum-Pacific tectonic regime

Geology in the Yanbian area, NE China, is a key to understanding the relationship between the Paleo-Pacific tectonic regime and the older Paleo-Asian oceanic regime, especially the transition between the regimes during the Mesozoic. A compilation of 131 U–Pb zircon ages, including 18 obtained in the present study, shows that the late Paleozoic to Mesozoic magmatism in the Yanbian area took place from 285 to 105Ma (mainly 205–160Ma) and that there was a peak of activity at ∼175Ma and a hiatus from the Late Jurassic to Early Cretaceous (150–130Ma). Provisionally, we subdivide the magmatic activity into four dominant stages: Middle Permian to Middle Triassic (280–240Ma), Late Triassic (230–205Ma), Early to Middle Jurassic (205–160Ma) and Early Cretaceous (130–105Ma). Middle Permian intrusive rocks, including pyroxenite, gabbro, diorite, granodiorite, tonalite and monzogranite, are interpreted to have been emplaced along an Andean-style continental margin in association with the subduction of the Paleo-Asian oceanic plate. The Late Permian–Middle Triassic intrusive rocks are mainly quartz monzonite, monzogranite and syenogranite, and are considered to have been the result of syn-orogenic/post-collisional activities. The Late Triassic magmatism involved not only the emplacement of mafic–ultramafic intrusive rocks, but also coeval I- and A-type granitoids, indicating an extensional environment after the final closure of the Paleo-Asian Ocean. Since the Jurassic, the tectonic setting has been dominated by subduction of the Paleo-Pacific oceanic plate. Previously published data for the Yanbian area and age data from surrounding regions show that the entire region from the Yanbian area to the Korean Peninsula and the Japanese Islands experienced peaks in igneous activities that ranged from 200 to 165Ma during the Jurassic, and 120 to 110Ma and 90 to 65Ma during the Cretaceous. The Jurassic intrusive rocks were emplaced mainly in the west and Cretaceous intrusive rocks in the east. In other words, there is a southeastwards younging of Mesozoic intrusive rocks that appears to have been closely associated with the evolution of the Paleo-Pacific Ocean. Taking all this into account, we conclude that the transition from the Paleo-Asian oceanic regime to the circum-Pacific tectonic regime took place during the Late Triassic to Early Jurassic.

Late Paleozoic pre- and syn-kinematic plutons of the Kangguer-Huangshan Shear zone: Inference on the tectonic evolution of the eastern Chinese north Tianshan

Permian large-scale transcurrent tectonics and massive magmatism are prominent features of the Tianshan belt and neighboring regions of the Central Asian Orogenic Belt. Structural, geochronological and geochemical analyses of Carboniferous and Permian intrusive rocks associated with the Kangguer--Huangshan Shear Zone (eastern Chinese North Tianshan) provide constraints on their tectonic setting and the tectonic evolution of the Tianshan belt as well. Carboniferous granitic rocks were emplaced at 338 ± 4 Ma and 347 ± 2 Ma, respectively, and show geochemical features typical of the calc-alkaline series. These arc-type granites do not display ductile deformation, probably because they were completely cooled at the time of shearing tectonics, and are only offset by brittle strike-slip faults. In contrast, Permian granitoids display pervasive ductile tectonic features diagnostic of synkinematic emplacement. Four gabbro and diorite samples from the East Huangshan intrusive complex yielded zircon U-Pb ages of 267 to 275 Ma, and a granitic dike is dated at 290 ± 1 Ma. The granitic dike is cut by en-echelon right-lateral strike-slip faults, and the mafic intrusive complex displays a sigmoidal shape with mylonitic foliation localized at its margins. Other specific pluton shapes (such as tongue and tadpole-like) and syn-magmatic deformation can be observed in intrusions of the same age, showing similar fabrics and kinematics consistent with that of the Kangguer--Huangshan Shear Zone. Numerous mafic to felsic dikes occur within and off the shear zone with a dominant SE-NW orientation and minor varieties in N-S or NNE-SSW directions. One gabbro dike that intrudes the early Carboniferous granite of the East Kanggurtag area yielded a magmatic age of 274 ± 4 Ma, and contains older zircons (∼340 Ma, ∼390 Ma, ∼450 Ma, and 1.3-2.2 Ga) probably inherited from intruded rocks. The Permian intrusive rocks have variable chemical compositions suggesting derivation of these rocks from depleted and undepleted (or enriched) mantle sources with involvement of subduction-related components. We conclude from our integrated analysis of the geological, structural, geochemical and geochronological data that the Permian magmatic rocks were formed in a post-collisional/post-orogenic setting from multiple sources, and were emplaced under the control of large-scale dextral transcurrent tectonics.

The timing and provenance record of the Late Permian Klondike orogeny in northwestern Canada and arc‐continent collision along western North America

The northern Canadian Cordillera exhibits coeval accreted arc, subduction zone, ocean basin, and continental margin assemblages that make the region an exceptional place to understand tectonic processes involved in arc‐continent collision. In this study, we use U‐Pb zircon and monazite geochronology to define the timing and provenance record of Late Permian collisional orogeny related to the accretion of the Yukon‐Tanana terrane onto the ancestral North American continental margin of northwestern Canada. New U‐Pb crystallization ages of Permian intrusive rocks in the Klondike District of western Yukon bracket the timing of collision‐related ductile deformation and greenschist‐ to amphibolite‐facies metamorphism on the Yukon‐Tanana terrane between 260 and 252.5 Ma. This tectonothermal event is herein named the Klondike orogeny. Detrital zircon U‐Pb geochronology of Triassic strata provides the sedimentary record of arc‐continent collision and crustal reworking along the Cordilleran margin. Arc‐derived detrital zircons in Early to Middle Triassic (251–235 Ma) strata overlying the ancestral North American continental margin in Yukon suggest that a foreland‐style basin developed adjacent to the Klondike orogen. Regionally extensive Late Triassic (235–200 Ma) strata containing primarily North American detrital zircons form an overlap assemblage that covered the accreted terranes and western North America. The timing of the Klondike orogeny is roughly synchronous with other contractional events along the ∼5000 km strike length of the Cordillera, including the Late Permian‐Early Triassic Sonoman orogeny in Nevada. Global plate reorganization linked to assembly of Pangaea may have been the tectonic engine for late Paleozoic‐early Mesozoic development of the North American Cordillera.

Tectono-metamorphic map of the Mont Morion Permian metaintrusives (Mont Morion—Mont Collon—Matterhorn Complex, Dent Blanche Unit), Valpelline—Western Italian Alps

Please click here to download the map associated with this article. The presented map displays the structural and metamorphic evolution of lithotypes from pre-Permian to present. We distinguish pre-Permian rocks (e.g., amphibolite, biotite-bearing gneiss and acid granulite) preserved as roof pendants (i.e., xenoliths) within Permian intrusives. Permian intrusives and hosted xenoliths are then re-equilibrated during Alpine evolution, producing coronitic to mylonitic metaintrusives, due to meter to kilometer-scale fabric gradients, and associated white mica-, glaucophane-bearing gneiss. The map also shows the traces of the superimposed foliations and the fold axial planes. The traces are distinguished on the basis of their relative chronology and mineralogical support. This information, reported on a single map, allows us to reconstruct the successive stages of this fragment belonging to the African plate continental crust, from the pre-Alpine extension, recorded by granulite- to amphibolite-facies xenolits, to the Permian intrusive phase (e.g., Mont Morion, Mont Collon and Matterhorn intrusives) lasting with the Alpine subduction-collision related evolution. The Mont Morion, part of the Mont Morion-Mont Collon-Matterhorn Complex of the Dent Blanche unit, may be interpreted as a multi-stadial Alpine km-scale shear zone, where Permian intrusive rocks are transformed into white mica chlorite-bearing or glaucophane-bearing gneisses along high-strain horizons (100 m-thick), while within low-strain cores (100- to 1000 m-thick), meta-intrusives preserve igneous features and xenoliths of amphibolites, acid granulites and biotite-bearing gneisses. In this paper, an outcrop tectono-metamorphic map (1:10,000 scale) is presented, based upon fieldwork at 1:5,000 together with an interpretative map (1:15,000 scale), in which three dimensional relationships are described, and micro- to mesoscopic fabric types are shown, corresponding to finite strain states recorded by rocks.

Cataclastic rocks along the Nesodden Fault, Oslo Region, Norway: a reactivated Precambrian shear zone

The Nesodden Fault Segment (NFS) is the northern segment of the Oslofjorden Fault (OF), which separates the Precambrian rocks in the east from Palaeozoic rocks in the west. The NFS is characterized by two groups of fault rocks. Group 1 comprises a series of crush breccias to ultracataclasites containing material derived from the Precambrian basement. These fault rocks were formed at a depth greater than 5 km, by attrition brecciation and distributed crush brecciation, at some time between the Sveconorwegian orogeny (950 Ma) and the deposition of the Cambrian Alum shale (540-505 Ma). Group 2 comprises five crush breccias with a similar quartz matrix containing fragments of older rocks and Permian intrusive rocks. They were formed at a depth of less than 3.5 km by the interaction of cataclasis and hydrothermal percolation (attrition- and implosion-brecciation), during the formation of the Permo-Carbonifereous Oslo Rift (300-230 Ma). Evidence of repeated hydrothermal fluid flow and fluidization has been recognized in the youngest breccias. The seven different fault rocks emphasize the importance of fault reactivation and show that old fault zones commonly act as planes of weakness along which repeated deformation takes place and act as pathways for hydrothermal fluids.