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Igneous activity and landforms
Published in Richard J. Chorley, Stanley A. Schumm, David E. Sugden, Geomorphology, 2019
Richard J. Chorley, Stanley A. Schumm, David E. Sugden
Igneous activity associated with the subduction zone is very complex in character. The subducting plate is subject to frictional heating, mineralogical phase changes (leading to additional heating), increasing pressure and metamorphism; these processes giving rise to a dominantly calc-alkaline suite of igneous rocks and being responsible for more than 80 per cent of the world’s present active volcanoes. These magmas are generated by a complex of processes involving partial melting of wet ultramafic rocks, melting and metamorphism of the descending oceanic crustal slab, fractionation of tholeiite, partial crustal melting and anatexis. Within the subduction zone diapirs of tholeiite are produced at shallow depths (80–100 km) and of andesite at greater depths (100–150 km). Pulses of subduction activity may result in variations of diastrophic and igneous activity in the subduction belt. For example, the lack of active volcanoes above a subduction zone (e.g. as in Ecuador and southern Peru at present) may imply a stationary subduction plate segment and a lack of magma generation. When subduction ceases, a basin may open up behind the volcanic belt and be filled with sediments and lava which become deformed on the resumption of subduction (Figure 6.4).
The hydrothermal sinter and kaolinite-Au-Ag occurrences of Ixtacamaxtitlán (Puebla, Mexico): preliminary results
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
A. Camprubí, J. Tritlla, R. Corona-Esquivel, E. Centeno, A. Terrazas
The study area is located in the Ixtacamaxtitlán municipality, in the northern half of the Puebla state in Central Mexico, close to the border with the Tlaxcala state (Fig. 1). The geological setting of the study area is defined by the junction of three major physiographic provinces: the limestone formations of Eastern Sierra Madre (ESM), the extrusive and intrusive felsic rocks of Western Sierra Madre (Mexican Ignimbritic Belt, or MIB), and the mafic volcanic rocks of the Trans-Mexican Volcanic Belt (TMVB). Little research on economic geology has been carried out in this zone, and only technical information on exploration for kaolin, issued by the Consejo de Recursos Minerales (Mexican Council for Mineral Resources), is available. Similar deposits, that were formerly exploited for kaolin, were reported by González-Reyna (1956), in Chignahuapan and Coayuca, close to Ixtacamaxtitlán, and may define a prospective area. An earlier report on the study area has been published by Camprubí et al. (2000). This area is presently under exploration by the Luismin Mining Company.
Simplified Seismic Assessment of a 16th Century Church and Cloister in Morelia, Mexico
Published in International Journal of Architectural Heritage, 2022
Guillermo Martinez, Jose Jara, Bertha Olmos, Lidia Mejia, Leslie Alejo
Morelia City is located inside the Trans-Mexican Volcanic Belt (TMVB) and it is affected by interplate, intraplate, or local fault earthquakes. The high seismic activity in the country relates to the subduction process of the Cocos Plate under the North American Plate (interplate fault), which is almost horizontal near to Acapulco City (Pérez-Campos et al. 2008), getting into the crust–mantle interface inside the Mexican Republic. The subduction process generates seismic events at depths lower than 45 km and the intraplate fractures produce earthquakes in the subducted oceanic slab in the range of 45–100 km, in an oblique zone of the Cocos Plate. The Trans-Mexican Volcanic Belt (TMVB) produces shallow earthquakes in central part of Mexico (Figure 1(b)), near to several populated cities (Suárez, Caballero-Jiménez, and Novelo-Casanova 2019). Although earthquakes in the TMVB have lower recurrence interval, it has produced large earthquakes in the past, many of them reported in the pre-Hispanic codices. Table 1 reports some of the earthquakes originated in the TMVB (Suárez, Caballero-Jiménez, and Novelo-Casanova 2019). One of them, occurred on June 19, 1858 had epicenter near the City of Morelia and the shaking lasted one and a half minute, damaged the Convents of Saint Agustin, the Jesus Company, and the Cathedral (García Acosta and Suárez 1996; Garduño‐Monroy et al. 2009).
Preservation of the Cadia Valley porphyry Au–Cu district, NSW, Australia: Silurian basin formation and subsequent inversion
Published in Australian Journal of Earth Sciences, 2021
M. Groome, R. M. Tosdal, A. C. Harris, I. G. Percival
The Cadia porphyry Au–Cu district lies in the Ordovician to early Silurian Macquarie Arc in the eastern Lachlan Orogen, one of the major structural belts forming the accreted Tasmanides along the eastern margin of the Australian craton (Fergusson, 2009, 2017; Glen, 2013; Gray & Foster, 2004; Rosenbaum, 2018). The Macquarie Arc is composed of predominantly subaqueous lavas, volcaniclastic deposits, and associated intrusions with a calc-alkalic to shoshonitic affinity (Crawford et al., 2007; Squire & Crawford, 2007). Magmatic activity in the Macquarie Arc commenced in the Early Ordovician and continued episodically for ca 50 Ma until it ceased in the early Silurian (Glen, Crawford, & Cooke, 2007; Glen, Crawford, Percival, et al.,2007; Meffre et al.,2007). The Macquarie Arc is generally considered to have formed over a west-dipping subduction zone (Percival & Glen, 2007). Conversely, Quinn et al. (2014) proposed the Macquarie Arc, which they referred to as the Macquarie Volcanic Belt, formed in a back-arc supra-subduction zone setting, and that the frontal arc lay somewhere to the east in present coordinates.
Age and tectonic significance of the Louth Volcanics: implications for the evolution of the Tasmanides of eastern Australia
Published in Australian Journal of Earth Sciences, 2018
R. C. Dwyer, W. J. Collins, A. C. Hack, R. Hegarty, H.-Q. Huang
The extent of the Louth Volcanics can be assessed using aeromagnetic data (Figure 1). The first vertical derivative (1VD) of total magnetic intensity (TMI) reduced-to-pole (RTP) data suggests that the Louth Volcanics consist of two main belts of high magnetic intensity that have been complexly folded. The intervening relatively non-magnetic regions are considered as an interlayered sedimentary pile. Interference fold geometry suggests that an early set of NNW-trending folds were refolded about E–W-trending structures. The NNW-trending volcanic belt centred on Louth is fault-bound on the west side, abutting zones of low magnetic intensity interpreted as clastic sedimentary rocks of the Winduck and Mulga Downs groups. Numerous small discrete magnetic highs cluster around, and in some cases disrupt, the two main belts of high magnetic intensity.