Rapid assembly and crystallization of a fossil large-volume silicic magma chamber

Eddy, Michael P.; Bowring, Samuel A.; Miller, Robert B.; Tepper, Jeffrey H.

doi:10.1130/g37631.1

Cited by 54 publications

(57 citation statements)

References 21 publications

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“…The magma flux estimates calculated here for the Questa batholith are similar to published estimates for other plutonic rocks (10 −3 to 10 −4 km 3 /a; e.g., de Silva & Gosnold, ; Eddy et al, ; Frazer et al, ; Mills & Coleman, ; Tappa et al, ). Our flux calculations are made using conservative estimates of pluton volume made on the basis of surface exposures and the Bouguer gravity low (Table ).…”

Section: Discussionsupporting

confidence: 86%

“…This model also makes predictions about the assembly and age of the batholith that cannot be tested without 3-D structural and geochronological control. Whereas a Bouguer gravity low provides evidence that there may be a volume of low-density silicic intrusive rocks at depth, age control on that volume is generally limited to 2-D surface exposures and vertical relief (e.g., Eddy et al, 2016;Frazer et al, 2014;Leuthold et al, 2012), except in locations where postemplacement structure has tilted the batholith and provided vertical control (e.g., Miller et al, 2011;Samperton et al, 2015). Simplified map of the Latir magmatic center showing the caldera outline and plutonic rocks of the (left) Questa batholith exposed at the surface and (right) Bouguer gravity anomaly.…”

Section: Introductionmentioning

confidence: 99%

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Geochronology of a Bouguer Gravity Low

et al. 2019

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Dense drill core and subsurface mapping at the Questa molybdenum mine, combined with regional structural tilt, permit detailed 3‐D documentation of plutonic rocks in the Latir magmatic center, New Mexico. Integration of mapping with new and existing U‐Pb zircon geochronology (a total of 136 analyses from 15 intrusions) allows for examination of the space‐time evolution of the Bouguer gravity low associated with the magmatic center. The Questa batholith at Latir was assembled by discrete pulses of magma over a 5.5‐Ma interval (approximately 25.3–19.8 Ma) of generally downward stacking intrusions following the volcanic peak at 25.52 Ma. This contradicts interpretations that the Bouguer gravity lows here and elsewhere are the plutonic crystal cumulate residues left after extraction of large‐volume silicic magmas. Estimates of magma flux based on the volume of plutonic rocks inferred from gravity data combined with the extrapolation of geochronology of exposed surface rocks are questionable because the assumption that unexposed plutonic rocks are the same age as dated surface rocks directly above them likely underestimates the true range of ages.

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Section: Discussionsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Geochronology of a Bouguer Gravity Low

et al. 2019

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“…Correcting for potential underestimates of intrusive duration will affect estimates of magma flux. For example, Eddy et al [2016] determined a number of precise U-Pb ages on units of the Golden Horn batholith in Washington. For one unit, they determined five ages that spanned 26 ka and a corresponding high average emplacement rate of $0.0125 km 3 /yr, which they inferred was large enough to sustain a persistent magma chamber.…”

Section: Discussionmentioning

confidence: 99%

“…Examples of this include using several U-Pb ages on a plutonic body to determine the time interval over which it was emplaced [e.g., Coleman et al, 2004;Schaltegger et al, 2009]. This latter technique is becoming increasingly important as a method to estimate magma fluxes [e.g., Davis et al, 2012;Leuthold et al, 2012;Eddy et al, 2016;Caricchi et al, 2016]. Such determinations are used to estimate the time intervals over which plutons are emplaced, the longevity of magma chambers, the lifespans of large igneous provinces (LIPs), required thermal inputs to magmatic systems, and other aspects of the geology and geophysics of magma bodies.…”

Section: Introductionmentioning

confidence: 99%

Estimating the duration of geologic intervals from a small number of age determinations: A challenge common to petrology and paleobiology

Glazner

Sadler

2016

Geochem Geophys Geosyst

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The duration of a geologic interval, such as the time over which a given volume of magma accumulated to form a pluton, or the lifespan of a large igneous province, is commonly determined from a relatively small number of geochronologic determinations (e.g., 4–10) within that interval. Such sample sets can underestimate the true length of the interval by a significant amount. For example, the average interval determined from a sample of size n = 5, drawn from a uniform random distribution, will underestimate the true interval by 50%. Even for n = 10, the average sample only captures ∼80% of the interval. If the underlying distribution is known then a correction factor can be determined from theory or Monte Carlo analysis; for a uniform random distribution, this factor is n+1n−1. Systematic undersampling of interval lengths can have a large effect on calculated magma fluxes in plutonic systems. The problem is analogous to determining the duration of an extinct species from its fossil occurrences. Confidence interval statistics developed for species origination and extinction times are applicable to the onset and cessation of magmatic events.

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“…Zircons were separated by standard heavy mineral separation methods. A minimum of 140 grains per sample were randomly selected, mounted with standards (Black et al, ; Eddy et al, ; Sláma et al, ), and analyzed using a laser ablation‐inductively coupled plasma‐mass spectrometer (LA‐ICP‐MS) at the University of Washington. The data were reduced with Iolite using their Geochron Data Reduction Scheme to calculate U‐Pb ages uncorrected for common lead (Paton et al, ).…”

Section: Methodsmentioning

confidence: 99%

Collision Chronology Along the İzmir‐Ankara‐Erzincan Suture Zone: Insights From the Sarıcakaya Basin, Western Anatolia

et al. 2019

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Debate persists concerning the timing and geodynamics of intercontinental collision, style of syncollisional deformation, and development of topography and fold-and-thrust belts along the >1,700-km-long İzmir-Ankara-Erzincan suture zone (İAESZ) in Turkey. Resolving this debate is a necessary precursor to evaluating the integrity of convergent margin models and kinematic, topographic, and biogeographic reconstructions of the Mediterranean domain. Geodynamic models argue either for a synchronous or diachronous collision during either the Late Cretaceous and/or Eocene, followed by Eocene slab breakoff and postcollisional magmatism. We investigate the collision chronology in western Anatolia as recorded in the sedimentary archives of the 90-km-long Sarıcakaya Basin perched at shallow structural levels along the İAESZ. Based on new zircon U-Pb geochronology and depositional environment and sedimentary provenance results, we demonstrate that the Sarıcakaya Basin is an Eocene sedimentary basin with sediment sourced from both the İAESZ and Söğüt Thrust fault to the south and north, respectively, and formed primarily by flexural loading from north-south shortening along the syncollisional Söğüt Thrust. Our results refine the timing of collision between the Anatolides and Pontide terranes in western Anatolia to Maastrichtian-Middle Paleocene and Early Eocene crustal shortening and basin formation. Furthermore, we demonstrate contemporaneous collision, deformation, and magmatism across the İAESZ, supporting synchronous collision models. We show that regional postcollisional magmatism can be explained by renewed underthrusting instead of slab breakoff. This new İAESZ chronology provides additional constraints for kinematic, geodynamic, and biogeographic reconstructions of the Mediterranean domain.

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Rapid assembly and crystallization of a fossil large-volume silicic magma chamber

Cited by 54 publications

References 21 publications

Geochronology of a Bouguer Gravity Low

Geochronology of a Bouguer Gravity Low

Estimating the duration of geologic intervals from a small number of age determinations: A challenge common to petrology and paleobiology

Collision Chronology Along the İzmir‐Ankara‐Erzincan Suture Zone: Insights From the Sarıcakaya Basin, Western Anatolia

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