K-Ar ages of hornblends in andesite and dacite from the Cretaceous Kanmon Group, Southwest Japan.

Imaoka, Teruyoshi; Nakajima, Tsukasa; Itaya, Tetsumaru

doi:10.2465/ganko.88.265

Cited by 38 publications

(19 citation statements)

References 8 publications

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“…Exceptions are taxa from the uppermost Cretaceous, brackish, coastal deltaic deposits of Quintanilla la Ojada, Burgos, Spain (Berreteaga et al, 2011), from the ?Aptian Santana Formation of Brazil (Mayrinck et al, 2010, and references therein), and from the Aptian Dongmyeong Formation of Korea (Imaoka et al, 1993;Yabumoto et al, 2006). The Santana Formation is a mainly fluvial, deltaic, and lagoonallacustrine succession with occasional brief marine incursions from either the Central or South Atlantic oceans (Berthou, 1990;Martill and Wilby, 1993).…”

Section: Discussionmentioning

confidence: 96%

Albuliform fish remains (Teleostei, Elopomorpha) from the Lower Cretaceous (Valanginian) Wadhurst Clay Formation of the Wealden Supergroup of southeast England

Sweetman

2013

Journal of Vertebrate Paleontology

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Section: Discussionmentioning

confidence: 96%

Albuliform fish remains (Teleostei, Elopomorpha) from the Lower Cretaceous (Valanginian) Wadhurst Clay Formation of the Wealden Supergroup of southeast England

Sweetman

2013

Journal of Vertebrate Paleontology

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“…Sagong, Kwon, and Ree () suggested that Mesozoic magmatism and the formation of granitoid batholiths in the Korean Peninsula occurred during the Triassic (248–210 Ma) and Early Jurassic (197–158 Ma), forming more potential sources for the zircons within the KS1 sandstone. In addition, late Early Cretaceous zircons were derived from 105 Ma to 103 Ma andesitic to dacitic volcanic rocks (Imaoka, Nakajima, & Itaya, ; Matsuura, ) and from the 110–100 Ma Ryoke metamorphic rocks (Iizumi, Imaoka, & Kagami, ; Nakajima, Shirahase, & Shibata, ; Suzuki & Adachi, ).…”

Section: Discussionmentioning

confidence: 99%

“…The chondrite‐normalized average REE compositions of the potential igneous source rocks discussed above are shown in Figure . End‐members are used as representative examples of geochemical compositions and radiometric ages (Tables S7 and S8), including granodiorite pebbles presenting Permian age of 250.8 Ma (Rb–Sr age; Shimizu et al, ), Early Jurassic quartz diorite of 198.6 Ma (zircon U–Pb; Ishihara et al, ), and andesite of late Early Cretaceous Kanmon Group (Terakado & Masuda, ) that crops out close to a dated part of the same unit that yielded hornblende K–Ar ages of 105.2 Ma (Imaoka et al, ) and 103 Ma (Matsuura, 1998). The KS1 sandstone has chondrite‐normalized REE patterns that are similar to the compositions of the Early Jurassic granite and late Early Cretaceous volcanic rocks, in that they are light REE (LREE) enriched, have flat heavy REE (HREE) patterns, and are free of Eu anomalies (Figure ).…”

Section: Discussionmentioning

confidence: 99%

Detrital zircon multi‐chronology, provenance, and low‐grade metamorphism of the Cretaceous Shimanto accretionary complex, eastern Shikoku, Southwest Japan: Tectonic evolution in response to igneous activity within a subduction zone

et al. 2017

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Detrital zircon multi‐chronology combined with provenance and low‐grade metamorphism analyses enables the reinterpretation of the tectonic evolution of the Cretaceous Shimanto accretionary complex in Southwest Japan. Detrital zircon U–Pb ages and provenance analysis defines the depositional age of trench‐fill turbidites associated with igneous activity in provenance. Periods of low igneous activity are recorded by youngest single grain zircon U–Pb ages (YSG) that approximate or are older than the depositional ages obtained from radiolarian fossil‐bearing mudstone. Periods of intensive igneous activity recorded by youngest cluster U–Pb ages (YC1σ) that correspond to the younger limits of radiolarian ages. The YC1σ U–Pb ages obtained from sandstones within mélange units provide more accurate younger depositional ages than radiolarian ages derived from mudstone. Determining true depositional ages requires a combination of fossil data, detrital zircon ages, and provenance information. Fission‐track ages using zircons estimated YC1σ U–Pb ages are useful for assessing depositional and annealing ages for the low‐grade metamorphosed accretionary complex. These new dating presented here indicates the following tectonic history of the accretionary wedge. Evolution of the Shimanto accretionary complex from the Albian to the Turonian was caused by the subduction of the Izanagi plate, a process that supplied sediments via the erosion of Permian and Triassic to Early Jurassic granitic rocks and the eruption of minor amounts of Early Cretaceous intermediate volcanic rocks. The complex subsequently underwent intensive igneous activity from the Coniacian to the early Paleocene as a result of the subduction of a hot and young oceanic slab, such as the Kula–Pacific plate. Finally, the major out‐of‐sequence thrusts of the Fukase Fault and the Aki Tectonic Line formed after the middle Eocene, and this reactivation of the Shimanto accretionary complex as a result of the subduction of the Pacific plate.

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“…Occurrence of high magnesian andesite (basaltic andesite), however, has been reported from several areas in Southwest Japan ( Imaoka & Murakami 1979; Yamada et al 1979 ; Suzuki & Shiraki 1980; Imaoka et al 1989 ; Kimura & Kiji 1993; Matsumoto et al 1994 ). Imaoka et al (1993) reported K–Ar hornblende ages of 105 ± 3 Ma and 107 ± 3 Ma for high magnesian andesite in the western part of Southwest Japan. High magnesian andesite 20 km north of Kyoto has a similar K–Ar hornblende age of 108 ± 5 Ma ( Kimura & Kiji 1993).…”

Section: Discussionmentioning

confidence: 99%

Sr–Nd isotope ratios of gabbroic and dioritic rocks in a Cretaceous‐Paleogene granite terrain, Southwest Japan

2000

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Whole‐rock chemical and Sr and Nd isotope data are presented for gabbroic and dioritic rocks from a Cretaceous‐Paleogene granitic terrain in Southwest Japan. Age data indicate that they were emplaced in the late Cretaceous during the early stages of a voluminous intermediate‐felsic magmatic episode in Southwest Japan. Although these gabbroic and dioritic rocks have similar major and trace element chemistry, they show regional variations in terms of initial Sr and Nd isotope ratios. Samples from the South Zone have high initial 87Sr/86Sr (0.7063–0.7076) and low initial Nd isotope ratios (ɛNd, −2.5 to −5.3); whereas those from the North Zone have lower initial 87Sr/86Sr (usually less than 0.7060) and higher Nd isotope ratios (ɛNd, −0.8 to + 3.3). Regional variations in Sr and Nd isotope ratios are similar to those observed in granitic rocks, although gabbroic and dioritic rocks tend to have slightly lower Sr and higher Nd isotope ratios than granitic rocks in the respective zones. Limited variations in Sr and Nd isotope ratios among samples from individual zones may be attributed partly to a combination of upper crustal contamination and heterogeneity of the magma source. Contamination of magmas by upper crustal material cannot, however, explain the observed Sr and Nd isotope variations between samples from the North and South Zones. Between‐zone variations would reflect geochemical difference in magma sources. The gabbroic and dioritic rocks are enriched in large ion lithophile elements (LILE) and depleted in high field strength elements (HFSE), showing similar normal‐type mid‐ocean ridge basalt (N‐MORB) normalized patterns to arc magmas. Geochronological and isotopic data may suggest that some gabbroic and dioritic rocks are genetically related to high magnesian andesite. Alternatively, mantle‐derived mafic or intermediate rocks which were underplated beneath the crust may be also plausible sources for gabbroic and dioritic rocks. The magma sources (the mantle wedge and lower crust) were isotopically more enriched beneath the South Zone than the North Zone during the Cretaceous‐Paleogene. Sr and Nd isotope ratios of the lower crustal source of the granitic rocks was isotopically affected by mantle‐derived magmas, resulting in similar initial Sr and Nd isotope ratios for gabbroic, dioritic and granitic rocks in each zone.

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K-Ar ages of hornblends in andesite and dacite from the Cretaceous Kanmon Group, Southwest Japan.

Cited by 38 publications

References 8 publications

Albuliform fish remains (Teleostei, Elopomorpha) from the Lower Cretaceous (Valanginian) Wadhurst Clay Formation of the Wealden Supergroup of southeast England

Albuliform fish remains (Teleostei, Elopomorpha) from the Lower Cretaceous (Valanginian) Wadhurst Clay Formation of the Wealden Supergroup of southeast England

Detrital zircon multi‐chronology, provenance, and low‐grade metamorphism of the Cretaceous Shimanto accretionary complex, eastern Shikoku, Southwest Japan: Tectonic evolution in response to igneous activity within a subduction zone

Sr–Nd isotope ratios of gabbroic and dioritic rocks in a Cretaceous‐Paleogene granite terrain, Southwest Japan

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