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Advent of Continents: A New Hypothesis

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ABSTRACT

The straightforward but unexpected relationship presented here relates crustal thickness to magma type in the Izu-Ogasawara (Bonin) and Aleutian oceanic arcs. Volcanoes along the southern segment of the Izu-Ogasawara arc and the western Aleutian arc (west of Adak) are underlain by thin crust (10–20 km). In contrast those along the northern segment of the Izu-Ogasawara arc and eastern Aleutian arc are underlain by crust ~35 km thick. Interestingly, andesite magmas dominate eruptive products from the former volcanoes and mostly basaltic lavas erupt from the latter. According to the hypothesis presented here, rising mantle diapirs stall near the base of the oceanic crust at depths controlled by the thickness of the overlying crust. Where the crust is thin, melting occurs at relatively low pressures in the mantle wedge producing andesitic magmas. Where the crust is thick, melting pressures are higher and only basaltic magmas tend to be produced. The implications of this hypothesis are: (1) the rate of continental crust accumulation, which is andesitic in composition, would have been greatest soon after subduction initiated on Earth, when most crust was thin; and (2) most andesite magmas erupted on continental crust could be recycled from “primary” andesite originally produced in oceanic arcs.

No MeSH data available.


(a) Bathymetric features of the Aleutian arc system. The red line in the bathymetric map indicates the location of the bathymetry profile shown in Fig. 2b. The Generic Mapping Tools (GMT) software (version 4.5, https://www.soest.hawaii.edu/gmt) was used in the bathymetric data processing. Bathymetry is taken from ETOPO181 (http://www.ngdc.noaa.gov/mgg/global/global.html, date of access:09/03/2016). (b) Bathymetry of the Aleutian arc through the arc volcanoes, from Piip submarine volcano in the west to the Pavlof volcano on the Alaska Peninsula in the east. The bathymetric data were sampled at intervals of 0.015° (~1.1 km) along the track from ETOPO181 (http://www.ngdc.noaa.gov/mgg/global/global.html, date of access:09/03/2016). The water depths between volcanoes change drastically from the western Aleutian arc (west of Adak, 2,000–4,000 m) to the eastern Aleutian arc (east of Adak, 0–500 m).
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f2: (a) Bathymetric features of the Aleutian arc system. The red line in the bathymetric map indicates the location of the bathymetry profile shown in Fig. 2b. The Generic Mapping Tools (GMT) software (version 4.5, https://www.soest.hawaii.edu/gmt) was used in the bathymetric data processing. Bathymetry is taken from ETOPO181 (http://www.ngdc.noaa.gov/mgg/global/global.html, date of access:09/03/2016). (b) Bathymetry of the Aleutian arc through the arc volcanoes, from Piip submarine volcano in the west to the Pavlof volcano on the Alaska Peninsula in the east. The bathymetric data were sampled at intervals of 0.015° (~1.1 km) along the track from ETOPO181 (http://www.ngdc.noaa.gov/mgg/global/global.html, date of access:09/03/2016). The water depths between volcanoes change drastically from the western Aleutian arc (west of Adak, 2,000–4,000 m) to the eastern Aleutian arc (east of Adak, 0–500 m).

Mentions: Figure 2 shows the bathymetric features of the Aleutian arc system. The red line in Fig. 2a defines the bathymetry section shown in Fig. 2b, passing through the Aleutian arc volcanoes, from Piip submarine volcano in the west to Pavlof volcano on the Alaska Peninsula in the east. The water depths between volcanoes change drastically from the western Aleutians (west of Adak, 2,000–4,000 m) to the eastern Aleutians (east of Adak, 0–500 m). The range of water depths (<500 m) and crustal thicknesses (35–37 km) east of Adak are shown as a rectangle in Fig. 1d, and are consistent with the northern segment of the Izu-Ogasawara arcs. The crustal thickness west of Adak is not independently known. However, Fig. 1d suggests, based on the water depth between arc front volcanoes, that it could be similar to the thickness beneath the southern segment of the Izu-Ogasawara arcs, which is about 10–20 km thick (Fig. 2).


Advent of Continents: A New Hypothesis
(a) Bathymetric features of the Aleutian arc system. The red line in the bathymetric map indicates the location of the bathymetry profile shown in Fig. 2b. The Generic Mapping Tools (GMT) software (version 4.5, https://www.soest.hawaii.edu/gmt) was used in the bathymetric data processing. Bathymetry is taken from ETOPO181 (http://www.ngdc.noaa.gov/mgg/global/global.html, date of access:09/03/2016). (b) Bathymetry of the Aleutian arc through the arc volcanoes, from Piip submarine volcano in the west to the Pavlof volcano on the Alaska Peninsula in the east. The bathymetric data were sampled at intervals of 0.015° (~1.1 km) along the track from ETOPO181 (http://www.ngdc.noaa.gov/mgg/global/global.html, date of access:09/03/2016). The water depths between volcanoes change drastically from the western Aleutian arc (west of Adak, 2,000–4,000 m) to the eastern Aleutian arc (east of Adak, 0–500 m).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC5037404&req=5

f2: (a) Bathymetric features of the Aleutian arc system. The red line in the bathymetric map indicates the location of the bathymetry profile shown in Fig. 2b. The Generic Mapping Tools (GMT) software (version 4.5, https://www.soest.hawaii.edu/gmt) was used in the bathymetric data processing. Bathymetry is taken from ETOPO181 (http://www.ngdc.noaa.gov/mgg/global/global.html, date of access:09/03/2016). (b) Bathymetry of the Aleutian arc through the arc volcanoes, from Piip submarine volcano in the west to the Pavlof volcano on the Alaska Peninsula in the east. The bathymetric data were sampled at intervals of 0.015° (~1.1 km) along the track from ETOPO181 (http://www.ngdc.noaa.gov/mgg/global/global.html, date of access:09/03/2016). The water depths between volcanoes change drastically from the western Aleutian arc (west of Adak, 2,000–4,000 m) to the eastern Aleutian arc (east of Adak, 0–500 m).
Mentions: Figure 2 shows the bathymetric features of the Aleutian arc system. The red line in Fig. 2a defines the bathymetry section shown in Fig. 2b, passing through the Aleutian arc volcanoes, from Piip submarine volcano in the west to Pavlof volcano on the Alaska Peninsula in the east. The water depths between volcanoes change drastically from the western Aleutians (west of Adak, 2,000–4,000 m) to the eastern Aleutians (east of Adak, 0–500 m). The range of water depths (<500 m) and crustal thicknesses (35–37 km) east of Adak are shown as a rectangle in Fig. 1d, and are consistent with the northern segment of the Izu-Ogasawara arcs. The crustal thickness west of Adak is not independently known. However, Fig. 1d suggests, based on the water depth between arc front volcanoes, that it could be similar to the thickness beneath the southern segment of the Izu-Ogasawara arcs, which is about 10–20 km thick (Fig. 2).

View Article: PubMed Central - PubMed

ABSTRACT

The straightforward but unexpected relationship presented here relates crustal thickness to magma type in the Izu-Ogasawara (Bonin) and Aleutian oceanic arcs. Volcanoes along the southern segment of the Izu-Ogasawara arc and the western Aleutian arc (west of Adak) are underlain by thin crust (10&ndash;20&thinsp;km). In contrast those along the northern segment of the Izu-Ogasawara arc and eastern Aleutian arc are underlain by crust ~35&thinsp;km thick. Interestingly, andesite magmas dominate eruptive products from the former volcanoes and mostly basaltic lavas erupt from the latter. According to the hypothesis presented here, rising mantle diapirs stall near the base of the oceanic crust at depths controlled by the thickness of the overlying crust. Where the crust is thin, melting occurs at relatively low pressures in the mantle wedge producing andesitic magmas. Where the crust is thick, melting pressures are higher and only basaltic magmas tend to be produced. The implications of this hypothesis are: (1) the rate of continental crust accumulation, which is andesitic in composition, would have been greatest soon after subduction initiated on Earth, when most crust was thin; and (2) most andesite magmas erupted on continental crust could be recycled from &ldquo;primary&rdquo; andesite originally produced in oceanic arcs.

No MeSH data available.