scholarly journals A survey of Sierra Nevada magmatism using Great Valley detrital zircon trace-element geochemistry: View from the forearc

Lithosphere ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 603-619
Author(s):  
Kathleen DeGraaff Surpless ◽  
Diane Clemens-Knott ◽  
Andrew P. Barth ◽  
Michelle Gevedon
Keyword(s):  
Trace Element ◽  
Sierra Nevada ◽  
Detrital Zircon ◽  
Geochemical Data ◽  
Trace Element Geochemistry ◽  
Arc Magmatism ◽  
Forearc Basin ◽  
Element Geochemistry ◽  
Continental Arc ◽  
Great Valley

AbstractThe well-characterized Sierra Nevada magmatic arc offers an unparalleled opportunity to improve our understanding of continental arc magmatism, but present bedrock exposure provides an incomplete record that is dominated by Cretaceous plutons, making it challenging to decipher details of older magmatism and the dynamic interplay between plutonism and volcanism. Moreover, the forearc detrital record includes abundant zircon formed during apparent magmatic lulls, suggesting that understanding the long-term history of arc magmatism requires integrating plutonic, volcanic, and detrital records. We present trace-element geochemistry of detrital zircon grains from the Great Valley forearc basin to survey Sierra Nevadan arc magmatism through Mesozoic time. We analyzed 257 previously dated detrital zircon grains from seven sandstone samples of volcanogenic, arkosic, and mixed compositions deposited ca. 145–80 Ma along the length of the forearc basin. Detrital zircon trace-element geochemistry is largely consistent with continental arc derivation and shows similar geochemical ranges between samples, regardless of location along strike of the forearc basin, depositional age, or sandstone composition. Comparison of zircon trace-element data from the forearc, arc, and retroarc regions revealed geochemical asymmetry across the arc that was persistent through time and demonstrated that forearc and retroarc basins sampled different parts of the arc and therefore recorded different magmatic histories. In addition, we identified a minor group of Jurassic detrital zircon grains with oceanic geochemical signatures that may have provenance in the Coast Range ophiolite. Taken together, these results suggest that the forearc detrital zircon data set reveals information different from that gleaned from the arc itself and that zircon compositions can help to identify and differentiate geochemically distinct parts of continental arc systems. Our results highlight the importance of integrating multiple proxies to fully document arc magmatism, demonstrating that detrital zircon geochemical data can enhance understanding of a well-characterized arc, and these data may prove an effective means by which to survey an arc that is inaccessible and therefore poorly characterized.

THE VIEW FROM THE FOREARC: A SURVEY OF SIERRA NEVADA MAGMATISM USING GREAT VALLEY DETRITAL ZIRCON TRACE ELEMENT GEOCHEMISTRY

2017 ◽  
Author(s):  
Kathleen D. Surpless ◽  
◽  
Diane Clemens-Knott ◽  
Andrew Barth ◽  
Michelle L. Gevedon ◽  
...  
Keyword(s):  
Trace Element ◽  
Sierra Nevada ◽  
Detrital Zircon ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Great Valley

GREAT VALLEY GROUP DETRITAL ZIRCON TRACE ELEMENT SIGNATURES: A PARTIAL RECORD OF SIERRA NEVADA ARC MAGMATISM

2016 ◽  
Author(s):  
Joshua R. Hernandez ◽  
◽  
Bethany G. Rysak ◽  
Kathleen DeGraaff Surpless ◽  
Andrew P. Barth ◽  
...  
Keyword(s):  
Trace Element ◽  
Sierra Nevada ◽  
Detrital Zircon ◽  
Arc Magmatism ◽  
Great Valley Group ◽  
Great Valley

scholarly journals Tectonic Exhumation of the Central Alps Recorded by Detrital Zircon in the Molasse Basin, Switzerland

2020 ◽  
Author(s):  
Owen A. Anfinson ◽  
Daniel F. Stockli ◽  
Joseph C. Miller ◽  
Andreas Möller ◽  
Fritz Schlunegger
Keyword(s):  
Rare Earth ◽  
Trace Element ◽  
Detrital Zircon ◽  
Late Eocene ◽  
Tectonic Activity ◽  
Trace Element Geochemistry ◽  
Molasse Basin ◽  
Age Group ◽  
Central Alps ◽  
Element Geochemistry

Abstract. Eocene to Miocene sedimentary strata of the Northern Alpine Molasse Basin in Switzerland are well studied, yet they lack robust geochronologic and geochemical analysis of detrital zircon for provenance tracing purposes. Here, we present detrital zircon U-Pb ages coupled with rare earth and trace element geochemistry (petrochronology) to provide insights into the sedimentary provenance and to elucidate the tectonic activity of the central Alpine Orogen from the late Eocene to mid Miocene. Between 35–22.5 ± 1 Ma, the detrital zircon U-Pb age signatures were dominated by age groups of 300–370 Ma, 370–490 Ma, and 490–710 Ma, with minor Proterozoic age contributions. In contrast, from 21.5 ± 1 Ma to ~ 13.5 Ma (youngest preserved sediments), the detrital zircon U-Pb age signatures were dominated by a 252–300 Ma age group, with a secondary abundance of the 370–490 Ma age group, and only minor contributions of the 490–710 Ma age group. The Eo-Oligocene provenance signatures are consistent with interpretations that initial basin deposition primarily recorded exhumation and erosion of the Austroalpine orogenic cover and minor contributions from underlying Penninic units, containing reworked detritus from Variscan, Caledonian, and Cadomian orogenic cycles. The dominant 252–300 age group from the younger Miocene deposits is associated with the exhumation of Variscan-aged crystalline rocks of upper-Penninic basement units. Noticeable is the lack of Alpine-aged detrital zircon in all samples with the exception of one late Eocene sample, which reflects Alpine volcanism associated with incipient continent-continent collision. In addition, the rare earth and trace element data from the detrital zircon, coupled with zircon morphology and U/Th ratios, point to primarily igneous and rare metamorphic sources of zircon. The observed change in detrital input from Austroalpine to Penninic provenance in the Molasse Basin at ~ 22 Ma appears to be correlated with the onset of synorogenic extension of the Central Alps. Synorogenic extension accommodated by slip along the Simplon fault zone promoted updoming and exhumation the Penninic crystalline core of the Alpine Orogen. The lack of Alpine detrital zircon U-Pb ages in all Oligo-Miocene strata also shows that the Molasse Basin drainage network was not accessing the prominent Alpine age intrusions and metamorphic complexes located in the southern portion of the Central Alps.

Trace-element geochemistry of metabasaltic rocks from the Yukon-Tanana Upland and implications for the origin of tectonic assemblages in east-central Alaska

1999 ◽  
Vol 36 (10) ◽  
pp. 1671-1695 ◽  
Author(s):  
Cynthia Dusel-Bacon ◽  
Kari M Cooper
Keyword(s):  
Trace Element ◽  
Continental Margin ◽  
Ocean Floor ◽  
Late Triassic ◽  
Geochemical Data ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
East Central ◽  
The North ◽  
Augen Gneiss

We present major- and trace- element geochemical data for 27 amphibolites and six greenstones from three structural packages in the Yukon-Tanana Upland of east-central Alaska: the Lake George assemblage (LG) of Devono-Mississippian augen gneiss, quartz-mica schist, quartzite, and amphibolite; the Taylor Mountain assemblage (TM) of mafic schist and gneiss, marble, quartzite, and metachert; and the Seventymile terrane of greenstone, serpentinized peridotite, and Mississippian to Late Triassic metasedimentary rocks. Most LG amphibolites have relatively high Nb, TiO2, Zr, and light rare earth element contents, indicative of an alkalic to tholeiitic, within-plate basalt origin. The within-plate affinities of the LG amphibolites suggest that their basaltic parent magmas developed in an extensional setting and support a correlation of these metamorphosed continental-margin rocks with less metamorphosed counterparts across the Tintina fault in the Selwyn Basin of the Canadian Cordillera. TM amphibolites have a tholeiitic or calc-alkalic composition, low normalized abundances of Nb and Ta relative to Th and La, and Ti/V values of <20, all indicative of a volcanic-arc origin. Limited results from Seventymile greenstones indicate a tholeiitic or calc-alkalic composition and intermediate to high Ti/V values (27-48), consistent with either a within-plate or an ocean-floor basalt origin. Y-La-Nb proportions in both TM and Seventymile metabasalts indicate the proximity of the arc and marginal basin to continental crust. The arc geochemistry of TM amphibolites is consistent with a model in which the TM assemblage includes arc rocks generated above a west-dipping subduction zone outboard of the North American continental margin in mid-Paleozoic through Triassic time. The ocean-floor or within-plate basalt geochemistry of the Seventymile greenstones supports the correlation of the Seventymile terrane with the Slide Mountain terrane in Canada and the hypothesis that these oceanic rocks originated in a basin between the continental margin and an arc to the west.

Silurian and late Ordovician K-bentonites as a record of late Caledonian volcanism in the British Isles

1995 ◽  
Vol 86 (3) ◽  
pp. 167-180 ◽  
Author(s):  
N. J. Fortey ◽  
R. J. Merriman ◽  
W. D. Huff
Keyword(s):  
Trace Element ◽  
Function Analysis ◽  
Volcanic Rocks ◽  
Late Ordovician ◽  
Trace Element Geochemistry ◽  
British Isles ◽  
Element Geochemistry ◽  
Arc Volcanism ◽  
Iapetus Ocean ◽  
Continental Arc

AbstractSilurian and late Ordovician K-bentonites of the British Isles provide a record of prolonged volcanism during the convergence of terranes associated with closure of the Iapetus and Tornquist Oceans. In the Southern Uplands–Longford-Down and Midland Valley terranes, they range from late Caradoc to Telychian, withfurther early Homerian occurrences. South of the Iapetus suture, in Eastern Avalonia, the range is Hirnantianto early Ludlow in northern England and early Telychian to earliest Ludfordian in the Welsh Borderland and English Midlands. In both cases, the distributions indicate that volcanism was more long-lived and probably more extensive than is depicted in current plate tectonic reconstructions. Average intervals between K-bentonites are estimated, based on Harland et al. (1990), as: c. 65000 years at Dob's Linn (late Aeronian to early Telychian); c. 39000 years in the Cautley area (Telychian); c. 51000 years in a borehole at Walsall (late Llandovery to Sheinwoodian). Trace element geochemistry suggests mostly subalkaline dacitic to rhyolitic magmas in which LILE-enrichment accompanies variable enrichment in crustally derived elements (Ta, Nb). The geochemistry suggests comparison with continental arc volcanism of ‘withinplate, attenuated lithosphere’ character. Ta–Nb enrichment and an absence of Eu anomalies from REE profiles are consistently present northof the Iapetus suture, but trace element patterns are less consistent south of the suture where negative Eu anomalies are generally present. Discriminant function analysis successfully distinguishes Llandovery, Wenlockand Ludlow K-bentonites from south of the Iapetus suture, and Llandovery K-bentonites from north and south ofthe suture. Those from north of the Iapetus suture probably originated in volcanism along the southern marginof Laurentia before final closure of the Iapetus Ocean. Those from south of the suture may have been derived from volcanism associated with late destruction of Iapetus and Tornquist oceanic crust, although an alternative involving volcanism at the southern margin of Eastern Avalonia or Baltica may accord better with the distribution of K-bentonites and the geographical trend of the fragmentary outcrops of Silurian volcanic rocks from southern Ireland to Belgium.

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