Tectonic setting of the Slide Mountain terrane, southern British Columbia
41
Citation
44
Reference
10
Related Paper
Citation Trend
Abstract:
The Slide Mountain terrane (SMT) in southern British Columbia consists of rocks of continental and oceanic affinity that are juxtaposed with parautochthonous rocks of the North American continental margin. In southern British Columbia, SMT consists dominantly of fine‐grained quartzose clastic rocks, limestone and lesser amounts of conglomerate and volcanic rocks of the Carboniferous McHardy assemblage, and predominantly mafic volcanic rocks of the Permian Kaslo Group. U‐Pb ages of individual detrital zircons from the McHardy assemblage are 1.7 Ga to 3.1 Ga and are similar to published ages of zircons from sedimentary rocks of the adjacent Kootenay terrane and the North American continental margin. These data and the petrology of McHardy assemblage sandstones and conglomerate suggest Kootenay terrane and the North American miogeocline as sources for McHardy assemblage detritus. U‐Pb zircon ages of granitoid clasts within McHardy assemblage conglomerate indicate that Silurian granitic rocks also provided detritus to the SMT. Mafic volcanic, ultramafic, and sedimentary rocks of the Kaslo Group conformably overlie the McHardy assemblage. New geochemical data demonstrate that the Kaslo Group consists of light rare earth element depleted basalts. On the basis of geochemical and geologic data, we suggest that Kaslo Group volcanics were erupted within an ocean ridge proximal to the North American continental margin and probably represent the eastern (continental) margin of a Permian marginal basin. Lithologie, stratigraphie, and U‐Pb geochronologic data suggest that the SMT was deposited on autochthonous, distal miogeoclinal rocks of the adjacent western North American craton and in close proximity to an early Paleozoic arc terrane. We infer that correlative late Paleozoic basinal terranes in western North American were deposited in a similar tectonic setting.Keywords:
Conglomerate
Detritus
Continental Margin
We report zircon U–Pb geochronologic and geochemical data for the post-collisional volcanic rocks from the Batamayineishan (BS) Formation in the Shuangjingzi area, northwestern China. The zircon U–Pb ages of seven volcanic samples from the BS Formation show that the magmatic activity in the study area occurred during 342–304 Ma in the Carboniferous. The ages also indicate that the Palaeo-Karamaili Ocean had already closed by 342 Ma. Moreover, the volcanic rocks also contained 10 inherited zircons with ages ranging from 565 to 2626 Ma, indicating that Precambrian continental crust or microcontinents with accretionary arcs are two possible interpretations for the basement underlying the East Junggar terrane. The sampled mafic-intermediate rocks belong to the medium-K to high-K calc-alkaline and shoshonitic series, and the formation of these rocks involved fractional crystallization with little crustal contamination. These Carboniferous mafic-intermediate rocks show depletions in Nb and Ta and enrichments in large ion lithophile elements (e.g. Rb, Ba, U, and Th) and light rare earth elements. The low initial 87Sr/86Sr values (0.7034–0.7042) and positive εNd(t) values (+2.63 to +6.46) of these rocks suggest that they formed from depleted mantle material. The mafic-intermediate rocks were most likely generated by 5–10% partial melting of a mantle source composed primarily of spinel lherzolite with minor garnet lherzolite that had been metasomatized by slab-derived fluids and minor slab melts. In contrast, the felsic rocks in the BS Formation are A-type rhyolites with positive εNd(t) values and young model ages. These rocks are interpreted to be derived from the partial melting of juvenile basaltic lower crustal material. Taken together, the mafic-intermediate rocks formed in a post-collisional extensional setting generated by slap breakoff in the early Carboniferous (342–330 Ma) and the A-type rhyolites formed in a post-collisional extensional setting triggered by the upwelling asthenosphere in the late Carboniferous (330–304 Ma).
Felsic
Geochronology
Cite
Citations (29)
Ion microprobe U–Th–Pb analyses of baddeleyite and zircon yield precise ages for several mafic intrusions in the Pilbara Craton of Western Australia. Baddeleyite was dated from four dolerite dykes of the north‐northeast‐trending Black Range swarm intruded into granitoid‐greenstone basement in the northern part of the craton. The mean 207Pb*/206Pb* age of 2772 ± 2 Ma, interpreted as an unambiguous age of emplacement for the dykes, is within error of previous ion microprobe U–Pb zircon ages for the Mt Roe flood basalts and confirms that the dykes acted as feeders to the volcanic rocks. The Sylvania Inlier, in the southeastern Pilbara Craton, also contains north‐northeast‐trending dykes that were correlated previously with the Black Range swarm. Based on concordant and discordant zircon analyses from samples of two dykes, the best estimate of the age of the Sylvania dykes is 2747 ± 4 Ma. The Sylvania dykes thus appear to be significantly younger than, and hence unrelated to, the Black Range swarm, but may have acted as feeders to younger volcanic units in the Fortescue Group such as the Kylena Formation.
Baddeleyite
Flood basalt
Microprobe
Basement
Cite
Citations (68)
Massif
Detritus
Cite
Citations (43)
Felsic
Batholith
Lithic fragment
Detritus
Volcanic arc
Continental arc
Cite
Citations (19)
Conglomerate
Outcrop
Cite
Citations (0)
Widespread magmatic and metamorphic events during the interval 2350-1650 Ma suggest that the North China craton (NCC) may have been involved in the evolution of the supercontinent Columbia. Metamorphosed and unmetamorphosed dikes have been characterized in terms of their geochemistry and geochronology. Dike suite 1 in the northern Wutai-Fuping terrane comprises amphibolite-facies assemblages and has a SHRIMP U-Pb zircon crystallization age of 2147 ± 5 Ma. Dike suite 2, distributed in the northern part of the Huai'an-Fengzhen terrane, has a two-pyroxene granulite assemblage, and yields a SHRIMP metamorphic zircon age of 1929 ± 8 Ma. Dike suite 3 in the Sanggan structural zone between the two terranes is composed of garnet two-pyroxene granulites, and has a SHRIMP zircon age of 1973 ± 4 Ma for the cores and 1834 ± 5 Ma for the rims, defining the time of crystallization and peak metamorphism, respectively. Dike suites 1 and 2 were possibly emplaced close to a continental margin and an arc respectively; whereas dike suite 3 was most likely post-orogenic. Zircon grains from an unmetamorphosed mafic dike in the north-central NCC yields a SHRIMP crystallization age of 1778 ± 3 Ma. We suggest that the metamorphosed mafic dike suites probably resulted from the amalgamation of the NCC in the Columbia supercontinent between 2080 and 1980 Ma (~2000 Ma), whereas the unmetamorphosed mafic dike swarms probably was emplaced during its break-up at 1780-1750 Ma. The metamorphosed dikes were likely uplifted and exhumed during a plume-driven upwelling event during 1830-1750 Ma, causing intrusion of (unmetamorphosed) dikes throughout the NCC.
Dike
Cite
Citations (292)
Rodinia
Supercontinent
Felsic
Continental arc
Cite
Citations (20)
Geochronology
Felsic
Cite
Citations (0)
The clastic rocks of the Maoniushan Formation in Maoniushan area along the northern margin of the Qaidam terrane is a suit of nonmarine sedimentary rocks that deposited in the alluvial fan and fan-delta environments.The alluvial fan deposits,conglomerate to coarse-grained sandstone association,are primarily located in the SE.The fan delta deposits are mainly distributed in the NW and consist of sandstone and mudstone.Paleocurrent analysis indicates that the Maoniushan Formation deposits originated from an ancient uplift which located in the SE primarily,but some deposits of fan delta were drived from NW and NE.In combination with synchronic lacustrine and shallow-marine sediments in the southwest of the study area,the spatial changes of these sedimentary facies suggest that a NW-striking paleoslope should exist in Maoniushan area along the north margin of the Qaidam terrane in the late Silurian-early Devonian and the north side uplifted in the later period.Comparison between detrital components and regional rock assemblages demonstrates that the clastic sediments of the Maoniushan Formation mainly derived from the Tanjianshan Group.Sedimentary sequence and regional tectonic evolution coevally suggest that the Maoniushan Formation deposited within a graben basin in a convergent setting which was formed by the northward subduction of the Qaidam terrane.
Conglomerate
Paleocurrent
Alluvial fan
Devonian
Cite
Citations (1)