The Central Atlantic Magmatic Province extends into Bolivia

Bertrand, Hervé; Fornari, Michel; Marzoli, Andréa; García-Duarte, Raúl; Sempéré, Thierry

doi:10.1016/j.lithos.2013.10.019

Cited by 48 publications

(16 citation statements)

References 47 publications

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“…In terms of timing, the province was emplaced in ~ 1 Ma (Marzoli et al 1999;Blackburn et al 2013;Davies et al 2017;Heimdal et al 2018) which is similar to other well-known Phanerozoic LIPs (Siberian Traps, Karoo-Farrar, Deccan, Columbia river flood basalts Svensen et al 2012;Greber et al 2020;Kasbohm and Schoene 2018;Schoene et al 2019). The CAMP is, however, distinct from these other LIPs, since it has very few preserved flood basalt lava flows and contains gabbroic intrusions that cover an extremely large area over ~ 8000 km from northern France to southern Bolivia (Jourdan et al 2003;Bertrand et al 2014) with a volume of at least 3 million km 3 . The geochemistry of the CAMP rocks suggests that the province is comprised almost entirely of basalt and basaltic andesite compositions (SiO 2 in the range 48-55 wt.%), with no associated alkaline samples found so far, which is also quite distinct from other LIPs.…”

Section: Camp Magmatic Province Overviewmentioning

confidence: 58%

Zircon petrochronology in large igneous provinces reveals upper crustal contamination processes: new U–Pb ages, Hf and O isotopes, and trace elements from the Central Atlantic magmatic province (CAMP)

Davies

Marzoli

Bertrand

et al. 2021

Contrib Mineral Petrol

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Zircon occasionally crystallizes in evolved melt pockets in mafic large igneous province (LIP) magmas, and in these cases, it is used to provide high-precision age constraints on LIP events. The precision and accuracy of high-precision ages from LIPs are crucially important, because they may be implicated in mass extinctions. However, why zircon crystallizes in these magmas is not clearly understood, since their mafic compositions should limit zircon saturation. Here, we investigate the occurrence of zircon (and baddeleyite) in intrusive and extrusive mafic rocks from Central Atlantic Magmatic Province (CAMP) using petrography, trace-element analysis, Ti temperatures, Hf and oxygen isotopes, and high-precision U–Pb geochronology, along with petrological and thermal modeling. We provide new ages for CAMP sills that intruded into Paleozoic sediments in Brazil, indicating that the high and low Ti magmatism in this area occurred synchronously over 264 ± 57 ka. We show that upper crustal assimilation, especially of shales, during the emplacement of the CAMP likely led to zircon saturation. Assimilation of upper crustal sediments is also supported by high δ18O values and some rare negative εHf values in the zircon crystals. The only extrusive sample analyzed was the North Mountain basalt in Nova Scotia, Canada. This sample contains a large age variation in its zircon crystals (up to 4 Ma), and the older crystals have slightly more negative εHf values suggesting the presence of small (micron scale) xenocrystic cores associated with very late-stage sediment assimilation. However, the CAMP dataset as a whole suggests that the presence of xenocrystic cores is rare. Assuming no xenocrystic cores, and considering the zircon undersaturated nature of LIP mafic melts, the oldest zircon age clusters in a population should record the magma emplacement (or time when assimilation occurred), and the younger ages in a population are more likely to reflect Pb loss, especially given the high U concentrations of LIP zircon. Our identification of heterogeneous isotopic and elemental compositions in LIP zircon indicates that zircon in these magmas saturate in isolated minute melt pockets just before the system cools below its solidus.

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Section: Camp Magmatic Province Overviewmentioning

confidence: 58%

Zircon petrochronology in large igneous provinces reveals upper crustal contamination processes: new U–Pb ages, Hf and O isotopes, and trace elements from the Central Atlantic magmatic province (CAMP)

Davies

Marzoli

Bertrand

et al. 2021

Contrib Mineral Petrol

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“…2 ) suggests a similar magmatic origin and a relatively homogenous Hf isotopic signature over the entire length of the province. Other tracer isotope systems (Sr, Nd Pb and Os) have been previously used to investigate the source of the CAMP magmas, however these have been dominantly analysed by whole rock techniques and often show a large range in values suggesting variable amounts of crustal contamination or variable crustal input into the mantle source over the whole province (see refs 30 , 31 , 32 , 33 , 34 , 35 ). The consistency of the zircon data suggests that (1) either the resolution of the technique is not at the required level to observe contamination, or (2) the contamination did not significantly alter the Hf isotopic composition of the samples.…”

Section: Resultsmentioning

confidence: 99%

“…A total of 15 samples from across the CAMP were selected to undergo standard mineral separation procedures to extract zircon and baddeleyite crystals. All samples have been previously characterized geochemically (major elements, trace elements,±isotopes) to indicate that they are part of the CAMP 30 31 32 33 34 35 36 45 46 47 48 49 . Ten of these samples ( Fig.…”

Section: Methodsmentioning

confidence: 99%

End-Triassic mass extinction started by intrusive CAMP activity

et al. 2017

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The end-Triassic extinction is one of the Phanerozoic's largest mass extinctions. This extinction is typically attributed to climate change associated with degassing of basalt flows from the central Atlantic magmatic province (CAMP). However, recent work suggests that the earliest known CAMP basalts occur above the extinction horizon and that climatic and biotic changes began before the earliest known CAMP eruptions. Here we present new high-precision U-Pb ages from CAMP mafic intrusive units, showing that magmatic activity was occurring ∼100 Kyr ago before the earliest known eruptions. We correlate the early magmatic activity with the onset of changes to the climatic and biotic records. We also report ages from sills in an organic rich sedimentary basin in Brazil that intrude synchronously with the extinction suggesting that degassing of these organics contributed to the climate change which drove the extinction. Our results indicate that the intrusive record from large igneous provinces may be more important for linking to mass extinctions than the eruptive record.

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“…Triassic red beds and Jurassic basalts (Sempere, 1995;Bertrand et al, 2014) vary between 200 and 500 m thick, and are restricted to the western SAZ. Overlying Jurassic and Cretaceous rocks thicken from tens of meters in the Chaco plain (Uba et al, 2009) and eastern SAZ to ~1.5 km in the central and western SAZ (Plate 2).…”

mentioning

confidence: 99%

Shortening and structural architecture of the Andean fold-thrust belt of southern Bolivia (21°S): Implications for kinematic development and crustal thickening of the central Andes

et al. 2017

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Reliable crustal shortening estimates for the central Andes (South America) are a critical component in validating models of Cordilleran processes. In southern Bolivia, insight into crustal shortening and the kinematic development of the Andean thrust belt are limited by the lack of a unified structural evaluation across the entire width of the retroarc region. To address these shortcomings, we (1) estimate crustal shortening by integrating new geologic mapping with published geophysical data to construct a balanced cross section across the Subandean zone (SAZ), Interandean zone (IAZ), and Eastern Cordillera (EC) at 21°S; (2) develop a kinematic model for the retroarc thrust belt; and (3) estimate crustal budgets and average crustal thicknesses over the region. We estimate 337 ± 69 km (36% ± 7%) of total shortening (SAZ, 82 km; IAZ, 70 km; EC, 120 km; Altiplano, 65 km). The thrust belt developed from late Eocene time to the present by tectonic wedging and eastward emplacement of two ~10-12-km-thick basement thrust sheets that distribute slip into overlying sedimentary rocks. Our range of crustal shortening values can account for 90%-118% of the current retroarc crustal area. Assuming an initial crustal thickness of 35 km, the EC and Altiplano did not achieve modern crustal thicknesses (~65 km) until the present. However, assuming a 40-km-thick initial crust, the EC and Altiplano attained the critical thickness for either eclogitic phase changes or lower crustal flow (>45-50 km) by ca. 27-25 Ma, modern thicknesses by ca. 10 Ma, and currently exceed geophysically observed thicknesses by ~2.5-14.5 km; this suggests crustal losses significant enough to have affected hinterland surface elevation.

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The Central Atlantic Magmatic Province extends into Bolivia

Cited by 48 publications

References 47 publications

Zircon petrochronology in large igneous provinces reveals upper crustal contamination processes: new U–Pb ages, Hf and O isotopes, and trace elements from the Central Atlantic magmatic province (CAMP)

Zircon petrochronology in large igneous provinces reveals upper crustal contamination processes: new U–Pb ages, Hf and O isotopes, and trace elements from the Central Atlantic magmatic province (CAMP)

End-Triassic mass extinction started by intrusive CAMP activity

Shortening and structural architecture of the Andean fold-thrust belt of southern Bolivia (21°S): Implications for kinematic development and crustal thickening of the central Andes

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