Fault-assisted vertical pluton growth: Coastal Cordillera, north Chilean Andes

Grocott, John; Arévalo, Carlos; Welkner, Daniela; Cruden, Alexander

doi:10.1144/0016-76492007-165

Cited by 48 publications

(22 citation statements)

References 16 publications

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“…Another possibility is that some, or most, of the volume increase was accommodated by subsidence of the magma reservoir floor. Many granite plutons exhibit evidence for vertical growth by floor subsidence, either on faults or by downsagging 18,19,55 .…”

Section: Accommodation Of the Recharge Volumementioning

confidence: 99%

“…Floor subsidence would compensate for rapid transfer of large volumes of magma from deeper in the crust, and could be essentially aseismic if faulting occurs beneath the brittle-ductile crustal transition or in plutonic mush 19 . Whether large surface uplifts and strong seismicity would necessarily have accompanied the preMinoan recharge events postulated at Santorini is in our opinion an open question.…”

Section: Accommodation Of the Recharge Volumementioning

confidence: 99%

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Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano

Druitt

Costa

Deloule

et al. 2012

Nature

326

218

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Crystals in volcanic rocks provide records of magma-reservoir processes and timescales prior to eruptions 7. A crystal growing from a magmatic melt incorporates trace elements in quantities governed by thermodynamic and kinetic laws 8,9 . If the crystal is subsequently mixed into another melt, trace elements that 2 diffuse sufficiently fast will begin to re-equilibrate with the new host melt, generating intra-crystalline diffusion gradients than can be used to obtain time information [10][11][12] (Supplementary Fig. S1). (Fig. 1g). In some crystals, the core also contains a euhedral to anhedral inner core of An 88-58 ('calcic inner core' ; Fig 1 a, c). A spectrum of type 1 crystals is observed from those with thick rims (up to 100 µm), to those with thin rims, to those in which the rim is absent (Fig. 1f). In rimmed type 1 crystals the plagioclase in contact with the host glass is ~ An 40, whereas in rimless ones it is ~An 50 (i.e., the core composition). Rimmed type-1 crystals occur in pumices from all four eruptive phases, but rimless ones have only been observed in pumices from phase 4. Type 2 crystals are very rare; they are reversely zoned, with cores of An 36-30 mantled by rims identical to those of type 1 (Fig. 1e). The broad range of plagioclase compositions in Minoan pumice shows that the rhyodacite was the product of open-system magmatic processes involving multiple, compositionally diverse magmas.Trace elements were analysed in four rimmed type-1 crystals, one rimless type-1 crystal, some interstitial glasses and some inclusions of glass contained within the crystals ( Fig. 2; Tables S1 and S2). Mg, Sr and Ti are particularly useful elements for characterizing coexisting melt compositions and mixing time scales because they partition differently between melt and plagioclase 8 and diffuse at different rates. Mg diffuses faster than Sr 7 ; Ti probably diffuses slowly due to its high charge. Published An-dependent partition coefficients 8 were used to invert melt trace element contents to those of equivalent plagioclase (Fig. 2), and vice versa (Fig. 3).Rimmed type-1 crystals have core-to-rim gradients in all the three elements (Fig. 2). Rim compositions record equilibrium with the interstitial glass, but concentrations of Mg, Sr, and Ti in the cores and calcic inner cores are significantly higher than those calculated to be in equilibrium with the glass (green lines, Fig. 2). The rimless type-1 crystal has concentrations of Mg and Sr throughout that are too high to have been in equilibrium with the glass. None of these crystals resided in the host melt long enough for any of these the elements to reach total equilibrium with the host melt.This observation is reinforced by a comparison of calculated Mg, Ti, and Sr concentrations of melts in equilibrium with the different plagioclase zones (referred to as Mg melt , Sr melt , and Ti melt ), with those of Santorini lavas, pumices, and glasses. The latter represent an approximate liquid line of descent of the magmatic system 3 (Fig. 3a, b). The calculated c...

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Section: Accommodation Of the Recharge Volumementioning

confidence: 99%

Section: Accommodation Of the Recharge Volumementioning

confidence: 99%

Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano

Druitt

Costa

Deloule

et al. 2012

Nature

326

218

View full text Add to dashboard Cite

show abstract

“…(5) sinking of intrusions that become denser than their surrounding country rocks following crystallization (e.g., Glazner, 1994;Weinberg and Podladchikov, 1995;Glazner and Miller, 1997;Johnson et al, 1999); and (6) fl oor depression (e.g., Wiebe, 1994;Cruden, 1998Cruden, , 2006Cruden and McCaffrey, 2001;Grocott et al, 2009). With rare exceptions (e.g., Paterson and Farris, 2008;Grocott et al, 2009), ambiguity persists owing to lack of three-dimensional geometric and kinematic constraints.…”

Section: Introductionmentioning

confidence: 99%

“…With rare exceptions (e.g., Paterson and Farris, 2008;Grocott et al, 2009), ambiguity persists owing to lack of three-dimensional geometric and kinematic constraints.…”

Section: Introductionmentioning

confidence: 99%

Coupled deformation and metamorphism in the roof of a tabular midcrustal igneous complex

Johnson

Jin

Naus-Thijssen

et al. 2011

Geological Society of America Bulletin

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The 370-377 Ma Mooselookmeguntic igneous complex was emplaced at ~14 km depth into steeply dipping metaturbidites that were folded and metamorphosed ca. 400-405 Ma during the Acadian orogeny. Gravity and drill-hole data, isograd geometry, thermal modeling, and structural measurements all indicate that the eastern aureole of the complex represents an areally extensive roof above the gently east-dipping, tabular-shaped intrusion. This roof preserves a classic example of lowpressure, high-temperature metamorphism caused by the underlying intrusion. Thermal modeling indicates that the roof is no more than 1000 m thick over an area exceeding 100 km 2 . Unlike other roofs described in the literature, the Mooselookmeguntic igneous complex roof preserves a thick (~600 m) emplacement-related strain gradient with a deformational fabric that evolved through all stages of crenulation cleavage to become an intense, nondifferentiated foliation approximately parallel to the intrusive contact and perpendicular to the steeply dipping, regional Acadian-age foliation. Fabric evolution through all stages of crenulation cleavage requires the vertical growth of the tabular intrusion to have been largely accommodated by dissolution-precipitation creep, which is a linear viscous deformation mechanism that can occur at lower differential stress than, for example, dislocation creep. As the crenulation cleavage evolves, a stage is reached where further deformation requires a change in deformation mechanism, which may lead to "hardening" of the rock. Development of crenulation cleavage requires a mica-rich foliation at an initially high angle to the emplacement-related fl attening plane, and this confi guration may be the primary reason why the strain aureole in the Mooselookmeguntic igneous complex roof is so well developed compared to other published examples of midcrustal roofs.

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“…Whether this fault acted as a feeding system for HVC laccoliths, as e.g. Grocott et al (2009) documented for plutons in northern Chile, is not known. The HVC is dominated by rhyolitic laccoliths .…”

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confidence: 99%

The Subvolcanic Units of the Late Paleozoic Halle Volcanic Complex, Germany: Geometry, Internal Textures and Emplacement Mode

Breitkreuz

Ehling²,

Pastrik

2015

Physical Geology of Shallow Magmatic Systems

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The Late Paleozoic Halle Volcanic Complex (HVC) formed in the Saale basin, a NE-SW-trending intermountain depositional system located in the Variscan orogen in Central Europe. Apart from minor lava flows and pyroclastic deposits, the HVC is dominated by a c. 300 km³ rhyolitic laccolith complex. The individual porphyritic rhyolite units display aspect ratios between 0.04 and 0.07. They initially emplaced at different levels of the Saale basin fill. As a consequence, the units are separated by tilted host sediments. Precursory to the emplacement of the rhyolitic laccoliths, a small-volume intermediate sill complex formed at the northern margin of the HVC. This chapter summarizes knowledge on the geometry, composition, internal textures, age, and host rock deformation of the HVC subvolcanic units.

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Fault-assisted vertical pluton growth: Coastal Cordillera, north Chilean Andes

Cited by 48 publications

References 16 publications

Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano

Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano

Coupled deformation and metamorphism in the roof of a tabular midcrustal igneous complex

The Subvolcanic Units of the Late Paleozoic Halle Volcanic Complex, Germany: Geometry, Internal Textures and Emplacement Mode

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