Interactive Material. Influence of pre-existing structure on pluton emplacement and geomorphology: The Merrimac plutons, northern Sierra Nevada, California, USA

Influence of pre-existing structure on pluton emplacement and geomorphology: The Merrimac plutons, northern Sierra Nevada, California, USA

10.1130/geos.s.13315613.v1 ◽

2020 ◽

Author(s):

V.E. Langenheim ◽

et al.

Keyword(s):

Trace Element ◽

Sierra Nevada ◽

Pluton Emplacement ◽

Age Range ◽

Existing Structure

<p></p><p>Figures 2–5, 7–9, and 13 are interactive. For Figures 2–5, 9, and 13, use the radio buttons to toggle between different maps. For Figure 7, use the radio buttons to toggle between age range variations and uncertainties for different samples in each pluton. For Figure 8, use the radio buttons to toggle between zircon trace element compositions of different plutons.</p><p></p>

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Influence of pre-existing structure on pluton emplacement and geomorphology: The Merrimac plutons, northern Sierra Nevada, California, USA

10.1130/geos.s.13315613 ◽

2020 ◽

Author(s):

V.E. Langenheim ◽

et al.

Keyword(s):

Trace Element ◽

Sierra Nevada ◽

Pluton Emplacement ◽

Age Range ◽

Existing Structure

<p></p><p>Figures 2–5, 7–9, and 13 are interactive. For Figures 2–5, 9, and 13, use the radio buttons to toggle between different maps. For Figure 7, use the radio buttons to toggle between age range variations and uncertainties for different samples in each pluton. For Figure 8, use the radio buttons to toggle between zircon trace element compositions of different plutons.</p><p></p>

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Supplemental Material: Influence of pre-existing structure on pluton emplacement and geomorphology: The Merrimac plutons, northern Sierra Nevada, California, USA

10.1130/geos.s.13315661 ◽

2020 ◽

Author(s):

V.E. Langenheim ◽

et al.

Keyword(s):

Sierra Nevada ◽

Pluton Emplacement ◽

Existing Structure

<div>Age and trace chemistry for Merrimac and other plutons, recalculation of previous Merrimac ages, and examples of Merrimac pluton textures. <br></div>

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Supplemental Material: Influence of pre-existing structure on pluton emplacement and geomorphology: The Merrimac plutons, northern Sierra Nevada, California, USA

10.1130/geos.s.13315661.v1 ◽

2020 ◽

Author(s):

V.E. Langenheim ◽

et al.

Keyword(s):

Sierra Nevada ◽

Pluton Emplacement ◽

Existing Structure

<div>Age and trace chemistry for Merrimac and other plutons, recalculation of previous Merrimac ages, and examples of Merrimac pluton textures. <br></div>

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Magmatic strains and foliation triple points of the Merrimac plutons, northern Sierra Nevada, California: implications for pluton emplacement and timing of subduction

Journal of Structural Geology ◽

10.1016/0191-8141(93)90094-q ◽

1993 ◽

Vol 15 (2) ◽

pp. 177-189 ◽

Cited By ~ 14

Author(s):

Giovanni Guglielmo

Keyword(s):

Sierra Nevada ◽

Pluton Emplacement ◽

Triple Points

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Influence of pre-existing structure on pluton emplacement and geomorphology: The Merrimac plutons, northern Sierra Nevada, California, USA

Geosphere ◽

10.1130/ges02281.1 ◽

2021 ◽

Author(s):

V.E. Langenheim ◽

J.A. Vazquez ◽

K.M. Schmidt ◽

G. Guglielmo ◽

D.S. Sweetkind

Keyword(s):

Sierra Nevada ◽

Drainage Density ◽

Magnetic Data ◽

Surface Uplift ◽

Western Cordillera ◽

Gravity And Magnetic ◽

Landscape Morphology ◽

Depth Extent ◽

Gravity And Magnetic Data ◽

Existing Structure

In much of the western Cordillera of North America, the geologic framework of crustal structure generated in the Mesozoic leaves an imprint on later plutonic emplacement, subsequent structural setting, and present landscape morphology. The Merrimac plutons in the northern Sierra Nevada (California, USA) are a good example of the influence of pre-existing structure at a larger scale. This paper updates and refines earlier studies of the Merrimac plutons, with the addition of analysis of gravity and magnetic data and new 206Pb/238U zircon dates. The gravity and magnetic data not only confirm the presence of two different neighboring plutons, but also (1) support the presence of a third pluton, (2) refine the nature of the contact between the Merrimac plutons as being structurally controlled, and (3) estimate the depth extent of the plutons to be ~4–5 km. The zircon 206Pb/238U dates indicate that the two main plutons have statistically different crystallization ages nearly 4 m.y. apart. Geomorphic analyses, including estimates of relief, roughness and drainage density and generation of chi plots, indicate that the two main plutons are characterized by different elevations with large longitudinal channel knickpoints that we speculatively attribute to possible reactivation of pre-existing structure in addition to lithologic variations influencing relative erosion susceptibility in response to prior accelerated surface uplift.

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O STOCK NEFELINA-SIENÍTICO RIO PARDO, PROVÍNCIA ALCALINA DO SUL DO ESTADO DA BAHIA

Revista Geonomos ◽

10.18285/geonomos.v20i1.22 ◽

2012 ◽

Cited By ~ 1

Author(s):

Rita da Cunha Leal Menezes ◽

Herbet Conceição ◽

Maria de Lourdes da Silva Rosa ◽

Marco Antonio Galarza ◽

Débora Correia Rios ◽

...

Keyword(s):

Rare Earth ◽

Trace Element ◽

Nepheline Syenite ◽

Crystallization Process ◽

The South ◽

Trace Element Contents ◽

Single Zircon ◽

Age Range ◽

Fractional Crystallization Process ◽

Zircon Evaporation

O Stock Nefelina-Sienítico Rio Pardo se localiza na porção sul do conjunto de intrusões alcalinas que constitui a Província Alcalina do Sul do Estado da Bahia. Esse corpo aflora numa área de 46 km2, sendo constituído por sienito, sienito com nefelina, nefelina sienito e sodalita sienito. A idade Pb-Pb obtida em monocristal de zircão para esse stock foi de 725 ± 2 Ma, a qual se insere no intervalo de idades para o magmatismo da parte sul dessa província alcalina (732 Ma a 720 Ma). Os dados litoquímicos obtidos para esse stock o posicionam na suíte alcalina subsaturada em SiO2 da Província Alcalina do Sul do Estado da Bahia. Os conteúdos de elementos traços asseguram sua afinidade anorogênica. Sua evolução, controlada por cristalização fracionada, se marca por acentuado enriquecimento em Na2O (até 15%) e Al2O3 (até 25%) e marcantes decréscimos em SiO2 (63% a 45%) e Elementos Terras Raras.Palavras-chave: nefelina sienito, idade Pb-Pb, Rio Pardo, BahiaABSTRACT: THE RIO PARDO NEPHELINE-SYENITIC STOCK, SOUTH BAHIA ALKALINE PROVINCE. The Rio Pardo nepheline-syenitic intrusion is located in the southern sector of the South Bahia Alkaline Province. It crops out over an area of 46 km2 and consists of syenite, nepheline-bearing syenite, nepheline syenite and blue-sodalite syenite. The Pb-Pb single-zircon evaporation age of 725 ± 2 Ma obtained for the Rio Pardo stock is in agreement with the age range (732 Ma to 720 Ma) for the southern part of province. Lithochemical data provide evidence to consider the Rio Pardo stock as a body of the SiO2 sub-saturated alkaline suite of the South Bahia Alkaline Province. Trace element contents indicate anorogenic afinity and the stock evolution, controlled by a fractional crystallization process, resulted in an outstanding enrichment of Na2O (up to 15%) and Al2O3 (up to 25%), and an important depletion of SiO2 (63% to 45%) and Rare Earth Elements.Keywords: nepheline syenite, Pb-Pb age, Rio Pardo, Bahia State.,

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Monitoring of Sierra Nevada Caves Reveals the Potential for Stalagmites to Archive Seasonal Variability

Frontiers in Earth Science ◽

10.3389/feart.2021.781526 ◽

2021 ◽

Vol 9 ◽

Author(s):

Barbara E. Wortham ◽

Isabel P. Montañez ◽

Kimberly Bowman ◽

Daphne Kuta ◽

Nora Soto Contreras ◽

...

Keyword(s):

Trace Element ◽

Sierra Nevada ◽

Seasonal Variability ◽

Large Variability ◽

Study Region ◽

Rock Interaction ◽

Drip Water ◽

Element Concentrations ◽

Cave Drip Water ◽

Precipitation And Temperature

In the southwestern United States, California (CA) is one of the most climatically sensitive regions given its low (≤250 mm/year) seasonal precipitation and its inherently variable hydroclimate, subject to large magnitude modulation. To reconstruct past climate change in CA, cave calcite deposits (stalagmites) have been utilized as an archive for environmentally sensitive proxies, such as stable isotope compositions (δ18O, δ13C) and trace element concentrations (e.g., Mg, Ba, Sr). Monitoring the cave and associated surface environments, the chemical evolution of cave drip-water, the calcite precipitated from the drip-water, and the response of these systems to seasonal variability in precipitation and temperature is imperative for interpreting stalagmite proxies. Here we present monitored drip-water and physical parameters at Lilburn Cave, Sequoia Kings Canyon National Park (Southern Sierra Nevada), CA, and measured trace element concentrations (Mg, Sr, Ba, Cu, Fe, Mn) and stable isotopic compositions (δ18O, δ2H) of drip-water and for calcite (δ18O) precipitated on glass substrates over a two-year period (November 2018 to February 2021) to better understand how chemical variability at this site is influenced by local and regional precipitation and temperature variability. Despite large variability in surface temperatures and precipitation amount and source region (North Pacific vs. subtropical Pacific), Lilburn Cave exhibits a constant cave environment year-round. At two of the three sites within the cave, drip-water δ18O and δ2H are influenced seasonally by evaporative enrichment. At a third collection site in the cave, the drip-water δ18O responds solely to precipitation δ18O variability. The Mg/Ca, Ba/Ca, and Sr/Ca ratios are seasonally responsive to prior calcite precipitation at all sites but minimally to water-rock interaction. Lastly, we examine the potential of trace metals (e.g., Mn2+ and Cu2+as a geochemical proxy of recharge and find that variability in their concentrations has high potential to denote the onset of the rainy season in the study region. The drip-water composition is recorded in the calcite, demonstrating that stalagmites from Lilburn Cave, and potentially more regionally, could record seasonal variability in weather even during periods of substantially reduced rainfall.

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