| Title | Was the late Cretaceous-Paleocene magmatic firestorm caused by slab failure? |
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| Author | Hildebrand, R S; Whalen, J B |
| Source | Geological Society of America, Abstracts With Programs vol. 46, no. 5, 2014 p. 73 |
| Links | Online - En ligne
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| Year | 2014 |
| Alt Series | Earth Sciences Sector, Contribution Series 20140244 |
| Publisher | Geological Society of America |
| Meeting | Geological Society of America Rocky Mountain and Cordilleran Joint Meeting; Bozeman, Montana; US; May 19-21, 2014 |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | html |
| Area | Cordillera |
| Subjects | igneous and metamorphic petrology; magmatism; Paleocene; Mesozoic; Cretaceous; Cenozoic; Tertiary |
| Program | GEM2: Geo-mapping for Energy and Minerals Western Cordillera Project Management |
| Released | 2014 01 01 |
| Abstract | Magmatism within the American Cordillera is commonly interpreted to have resulted from long-lived eastward subduction of Pacific oceanic lithosphere. However, the development of a model in which the
Americas collided with a composite arc-bearing ribbon continent above a westward-dipping subduction zone was recently confirmed by seismic tomography and invites actualistic models that involve both subduction-related and slab failure
magmatism.
Shut-down of arc magmatism in the ribbon continent just prior to 80 Ma, coupled with Late Cretaceous-Paleocene deformation in the Cordillera extending from Alaska to Tierra del Fuego, are interpreted to represent terminal collision of
the ribbon continent with the Americas. A period of intense magmatism, commonly mineralized, occurred during and after the deformation over most of its range. The magmatism is generally associated with linear belts of rapid exhumation, which
contrasts with the typical low-standing nature of magmatic arcs. These include the Late Cretaceous-Paleocene Alaska Range-Talkeetna Mountains magmatic belt; the Late Cretaceous-Paleocene syn-to post-deformational Ruby Range suite, as well as the
Carmacks, Donjek, Tlansanlin, and Mount Creedon volcanics of the Yukon; the 1500 km-long band of syn-deformational tonalite sills of the Coast plutonic complex of British Columbia; and rocks of the 80-64 Ma Boulder batholith and associated Elkhorn
volcanics, the 80 Ma Two Medicine, and the 75 Ma Adel volcanics of the northern US. In the Great Basin area magmatism is present only in the 75-50 Ma Colorado Mineral belt. From the Sonoran desert region of Arizona southward into Mexico a linear band
of 76-55 Ma magmatism and associated porphyry copper deposits occurs. In South America, 73-62 Ma centered complexes and belt-parallel dike swarms of the Coastal batholith followed terminal collision as did magmatism of the 75-60 Ma Neunauco belt of
northern Argentina.
A slab failure origin of the magmatism explains its distribution over the length of the Americas, its relationships to the deformation and contemporaneous exhumation, its commonly metalliferous nature, and its general absence
in the Great Basin sector due to previous slab failure there during the Sevier event. Many slab failure magmas with SiO2>60% have Sr/Y>20, Nb/Y>0.4, La/Yb>10, and Gd/Yb>2.0. |
| Summary | (Plain Language Summary, not published)
This abstract presents a novel new model for the tectonic setting of a major plutonic event in the Cordilleran orogen of NA. These igneous rocks host a
high proportion of intrusion-related deposits (Au-Cu-Mo) in Sthe Cordillera. The authors proposed model provides a new context for understanding the mineralizing potential of intrusion related systems. The results of this research are applicable to
understanding intrusion-related systems of different ages in Canada. |
| GEOSCAN ID | 295315 |
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