Influence of Late Cretaceous magmatism on the Sevier orogenic wedge, western Montana

Geology ◽  
2001 ◽  
Vol 29 (8) ◽  
pp. 723 ◽  
Author(s):  
David R. Lageson ◽  
James G. Schmitt ◽  
Brian K. Horton ◽  
Thomas J. Kalakay ◽  
Bradford R. Burton
Keyword(s):  
Late Cretaceous ◽  
Western Montana ◽  
Orogenic Wedge ◽  
Cretaceous Magmatism

Late Cretaceous granitoids of the Sikhote–Alin orogenic belt, southeastern Russia: implications for the Mesozoic geodynamic history of the eastern Asian continental margin

2021 ◽  
pp. jgs2021-109
Author(s):  
Igor V. Kemkin ◽  
Andrei V. Grebennikov ◽  
Xing-Hua Ma ◽  
Ke-Ke Sun
Keyword(s):  
Late Cretaceous ◽  
Pacific Plate ◽  
Orogenic Belt ◽  
Sikhote Alin ◽  
Asian Continent ◽  
Content Type ◽  
Eastern Margin ◽  
Continental Plate ◽  
Supplementary Material ◽  
Cretaceous Magmatism

We present new U–Pb age data for granitoids in the Central Sikhote–Alin orogenic belt in SE Russia, which refute the established opinion about the absence of the Late Cretaceous magmatism at the eastern margin of the Paleo-Asian continent. It was previously thought that a period of magmatic quiescence occurred from 88 to 50 Ma, related to subduction of the Paleo-Pacific Plate under the eastern margin of the Paleo-Asian continent, although this is inconsistent with evidence from the Sikhote–Alin, Sakhalin, and Japan regions. Three suites of plutonic rocks with different ages were identified in this study. The first suite has ages of 105–92 Ma and formed in a syn-orogenic setting. The second (86–83 Ma) and third (ca. 73 Ma) suites formed during the post-orogenic stage of the Sikhote–Alin orogenic belt. The second and third suites were coeval with Late Cretaceous granitoids that formed in a suprasubduction continental arc known as the Eastern Sikhote–Alin volcanic–plutonic belt (ESAVPB). However, the studied rocks are located far inland from the ESAVPB. The ages of the studied granitoids coincide with the timing of a change in the angle of convergence between the Paleo-Pacific Plate and eastern margin of the Paleo-Asian continent. This change in motion of the oceanic plate with respect to the continental plate was probably caused by a rupture in the subducted slab (i.e., a slab tear), followed by asthenospheric upwelling and partial melting of the overlying crust, which ultimately generated post-orogenic intrusive magmatism.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5738616

Melt source and evolution of I-type granitoids in the SE Tibetan Plateau: Late Cretaceous magmatism and mineralization driven by collision-induced transtensional tectonics

Lithos ◽  
2016 ◽  
Vol 245 ◽  
pp. 258-273 ◽  
Author(s):  
Li-Qiang Yang ◽  
Jun Deng ◽  
Yildirim Dilek ◽  
Jian-Yin Meng ◽  
Xue Gao ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Late Cretaceous ◽  
Cretaceous Magmatism

Late Cretaceous magmatism in Madagascar: palaeomagnetic evidence for a stationary Marion hotspot

1998 ◽  
Vol 164 (1-2) ◽  
pp. 221-232 ◽  
Author(s):  
T.H Torsvik ◽  
R.D Tucker ◽  
L.D Ashwal ◽  
E.A Eide ◽  
N.A Rakotosolofo ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Cretaceous Magmatism

A Late Cretaceous felsic magmatic suite from the Tengchong Block, western Yunnan: integrated geochemical and isotopic investigation and implications for Sn mineralization

2020 ◽  
Vol 157 (8) ◽  
pp. 1316-1332
Author(s):  
Zhuanrong Sun ◽  
Guochen Dong ◽  
M Santosh ◽  
Xuanxue Mo ◽  
Pengsheng Dong ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
The Tibetan Plateau ◽  
Precambrian Basement ◽  
Tetrad Effect ◽  
Southeastern Part ◽  
Ore Formation ◽  
Fine Grained ◽  
Western Yunnan ◽  
Cretaceous Magmatism ◽  
Magmatic Suite

AbstractThe Tengchong Block within the Sanjiang Tethys belt in the southeastern part of the Tibetan plateau experienced a widespread intrusion of a felsic magmatic suite of granites in its central domain during Late Cretaceous times. Here, we investigate the Guyong and Xiaolonghe plutons from this suite in terms of their petrological, geochemical, and Sr–Nd, zircon U–Pb and Lu–Hf–O isotopic features to gain insights into the evolution of the Neo-Tethys. The Guyong pluton (76 Ma) is composed of metaluminous monzogranites, and the Xiaolonghe pluton (76 Ma) is composed of metaluminous to peraluminous medium- and fine-grained syenogranite. A systematic decrease in Eu, Ba, Sr, P and Ti concentrations; a decrease in Zr/Hf and LREE/HREE ratios; and an increase in the Rb/Ba and Ta/Nb ratios from the Guyong to Xiaolonghe plutons suggest fractional crystallization of biotite, plagioclase, K-feldspar, apatite, ilmenite and titanite. They also show the characteristics of I-type granites. The negative zircon εHf(t) isotopic values (−10.04 to −5.22) and high δ18O values (6.69 to 8.58 ‰) and the negative whole-rock εNd(t) isotopic values (−9.7 to −10.1) and high initial 87Sr/86Sr ratios (0.7098–0.7099) of the Guyong monzogranite suggest that these rocks were generated by partial melting of the Precambrian basement without mantle input. The zircon εHf(t) isotopic values (−10.63 to −3.04) and δ18O values (6.54 to 8.69 ‰) of the Xiaolonghe syenogranite are similar to the features of the Guyong monzogranite, and this similarity suggests a cogenetic nature and magma derivation from the lower crust that is composed of both metasedimentary and meta-igneous rocks. The Xiaolonghe fine-grained syenogranite shows an obvious rare earth element tetrad effect and lower Nb/Ta ratios, which indicate its productive nature with respect to ore formation. In fact, we discuss that the Sn mineralization in the region was possible due to Sn being scavenged from these rocks by exsolved hydrothermal fluids. We correlate the Late Cretaceous magmatism in the central Tengchong Block with the northward subduction of the Neo-Tethys beneath the Burma–Tengchong Block.

A new bird from the Upper Cretaceous Two Medicine Formation of Montana

2002 ◽  
Vol 39 (1) ◽  
pp. 19-26 ◽  
Author(s):  
David J Varricchio
Keyword(s):  
Late Cretaceous ◽  
Upper Cretaceous ◽  
New Genus ◽  
Articular Surface ◽  
Type Specimen ◽  
Depositional Environments ◽  
Western Montana ◽  
New Genus And Species ◽  
Basal Position

A partial humerus, ulna, and radius compose the type specimen of a new bird, Piksi barbarulna, new genus and species, from the Late Cretaceous (Campanian) Two Medicine Formation of western Montana. This ornithothoracine taxon differs from all other birds in having an enlarged dorsal epicondyle and a reduced ventral condyle on the humerus with corresponding modifications on the articular surface of the ulna. Among modern birds, Piksi is most similar to galliforms, but the paucity of unambiguous characters and its unusual morphology defy placement within any extant "order" and strongly questions any neornithine affinities. Instead, Piksi appears to have a fairly basal position within Ornithothoraces. Several morphologic features of Piksi occur in phylogenetically diverse but morphologically similar birds, such as galliforms, tinamous, and some columbiforms. The new bird comes from an inland, relatively dry paleo-environment. Atypical for a Cretaceous avian record dominated by waterfowl, Piksi appears to represents a heavy-bodied ground bird. Searching of inland depositional environments may yield new and ecologically distinct avian varieties.

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