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Granite is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground. It is common in the continental crust of Earth, where it is found in igneous intrusions. These range in size from dikes only a few centimeters across to batholiths exposed over hundreds of square kilometers.
A batholith is a large mass of intrusive igneous rock, larger than 100 km2 (40 sq mi) in area, that forms from cooled magma deep in Earth's crust. Batholiths are almost always made mostly of felsic or intermediate rock types, such as granite, quartz monzonite, or diorite.
Ancash is a department and region in northern Peru. It is bordered by the departments of La Libertad on the north, Huánuco and Pasco on the east, Lima on the south, and the Pacific Ocean on the west. Its capital is the city of Huaraz, and its largest city and port is Chimbote. The name of the region originates from the Quechua word anqash, from anqas ('blue') or from anka ('eagle').
Andesite is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende.
Anorthosite is a phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90–100%), with a minimal mafic component (0–10%). Pyroxene, ilmenite, magnetite, and olivine are the mafic minerals most commonly present.
The Cordillera Blanca is a mountain range in Peru that is part of the larger Andes range and extends for 200 kilometres (124 mi) between 8°08' and 9°58'S and 77°00' and 77°52'W, in a northwesterly direction. It includes several peaks over 6,000 metres (19,690 ft) high and 722 individual glaciers. The highest mountain in Peru, Huascarán, at 6,768 metres (22,205 ft) high, is located there.
The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South American Plate. The belt is subdivided into four main volcanic zones which are separated by volcanic gaps. The volcanoes of the belt are diverse in terms of activity style, products, and morphology. While some differences can be explained by which volcanic zone a volcano belongs to, there are significant differences within volcanic zones and even between neighboring volcanoes. Despite being a type location for calc-alkalic and subduction volcanism, the Andean Volcanic Belt has a broad range of volcano-tectonic settings, as it has rift systems and extensional zones, transpressional faults, subduction of mid-ocean ridges and seamount chains as well as a large range of crustal thicknesses and magma ascent paths and different amounts of crustal assimilations.
Volcanic passive margins (VPM) and non-volcanic passive margins are the two forms of transitional crust that lie beneath passive continental margins that occur on Earth as the result of the formation of ocean basins via continental rifting. Initiation of igneous processes associated with volcanic passive margins occurs before and/or during the rifting process depending on the cause of rifting. There are two accepted models for VPM formation: hotspots/mantle plumes and slab pull. Both result in large, quick lava flows over a relatively short period of geologic time. VPM's progress further as cooling and subsidence begins as the margins give way to formation of normal oceanic crust from the widening rifts.
The Andean orogeny is an ongoing process of orogeny that began in the Early Jurassic and is responsible for the rise of the Andes mountains. The orogeny is driven by a reactivation of a long-lived subduction system along the western margin of South America. On a continental scale the Cretaceous and Oligocene were periods of re-arrangements in the orogeny. Locally the details of the nature of the orogeny varies depending on the segment and the geological period considered.
A continental arc is a type of volcanic arc occurring as an "arc-shape" topographic high region along a continental margin. The continental arc is formed at an active continental margin where two tectonic plates meet, and where one plate has continental crust and the other oceanic crust along the line of plate convergence, and a subduction zone develops. The magmatism and petrogenesis of continental crust are complicated: in essence, continental arcs reflect a mixture of oceanic crust materials, mantle wedge and continental crust materials.
The Famatinian orogeny is an orogeny that predates the rise of the Andes and that took place in what is now western South America during the Paleozoic, leading to the formation of the Famatinian orogen also known as the Famatinian belt. The Famatinian orogeny lasted from the Late Cambrian to at least the Late Devonian and possibly the Early Carboniferous, with orogenic activity peaking about 490 to 460 million years ago. The orogeny involved metamorphism and deformation in the crust and the eruption and intrusion of magma along a Famatinian magmatic arc that formed a chain of volcanoes. The igneous rocks of the Famatinian magmatic arc are of calc-alkaline character and include gabbros, tonalites and granodiorites. The youngest igneous rocks of the arc are granites.
The Cordillera Blanca Fault Zone is a system of geological faults located next to Cordillera Blanca in the northern Peruvian Andes. The fault is considered the most active one in northern Peru. The last time the fault ruptured was in the 1500s or before. The fault zone forms the western boundary of Cordillera Blanca Batholith.
Choiyoi Group is a Permian and Triassic-aged group of volcano-sedimentary formations in Argentina and Chile. The group bears evidence of bimodal-style volcanism related to an ancient subduction zone that existed along the western margin of the supercontinent Gondwana.
The Vicuña Mackenna Batholith is a group of plutons in the Chilean Coast Range of northern Chile. The plutons of the batholith formed between the Early Jurassic and the Late Cretaceous. The magmas that formed the batholith originated in Earth's mantle and have not suffered any significant crustal contamination. A group of Early Cretaceous plutons were intruded syn-tectonically on the Atacama Fault.
The Coastal Batholith of Peru is a group of hundreds, if not thousands, of individual plutons that crop out near or at the coast of Peru. The batholith runs a length of ca. 1600 km. Most of the plutons of the batholith were intruded in an elongated coast-parallel extensional basin. The magma that formed the batholith's plutons is thought to have originated from the partial melting of hydrated basaltic rocks at the base of the crust during rifting (extension). Subsequently, the rift basin was inverted. During the ascent the magma followed vertical pathways but emplacement was mostly in the form of tabular bodies.
The Colangüil Batholith is a group of plutons in western Argentina between the latitudes of 29 and 31° S. The plutons of the batholith were emplaced and cooled in the Late Paleozoic and the Triassic. Runs in a north-south direction. The plutons of the batholith are intruded into volcanic rocks produced by the same plutons plus some earlier deformed basement. The most common rocks in the batholith are granodiorite, granite and leucogranite. The batholith contains also a dyke swarm of north-south trending dykes. Compared to other subduction-related batholiths around the Pacific Ocean Colangüil Batholith is more felsic.
Tonalite–trondhjemite–granodiorite (TTG) rocks are intrusive rocks with typical granitic composition but containing only a small portion of potassium feldspar. Tonalite, trondhjemite, and granodiorite often occur together in geological records, indicating similar petrogenetic processes. Post Archean TTG rocks are present in arc-related batholiths, as well as in ophiolites, while Archean TTG rocks are major components of Archean cratons.
The geology of Ecuador includes ancient Precambrian basement rock and a complex tectonic assembly of new sections of crust from formerly separate landmasses, often uplifted as the Andes or transformed into basins.
The geology of Peru includes ancient Proterozoic rocks, Paleozoic and Mesozoic volcanic and sedimentary rocks, and numerous basins and the Andes Mountains formed in the Cenozoic.
The Latir volcanic field is a large volcanic field near Questa, New Mexico, that was active during the late Oligocene to early Miocene, 28 to 22 million years ago (Ma). It includes the Questa caldera, in whose deeply eroded interior is located the Molycorp Questa molybdenum mine.
References
- ↑ Petford, Nick; Atherton, Michael (1996). "Na-rich Partial Melts from Newly Underplated Basaltic Crust: the Cordillera Blanca Batholith, Peru". Journal of Petrology . 37 (6): 1491–1521.
