Geochemical, petrographic, and stratigraphic analyses of the Portage Lake Volcanics of the Keweenawan CFBP: implications for the evolution of Main stage volcanism in Continental Flood Basalt Provinces

2021 ◽  
pp. SP518-2020-221
Author(s):  
W. R. Davis ◽  
M. A. Collins ◽  
T. O. Rooney ◽  
E. L. Brown ◽  
C. A. Stein ◽  
...  
Keyword(s):  
Trace Elements ◽  
Flow Analysis ◽  
Flood Basalt ◽  
Lava Flows ◽  
Rift System ◽  
Main Stage ◽  
Continental Flood Basalt ◽  
Content Type ◽  
Supplementary Material ◽  
Incompatible Trace Elements

AbstractContinental Flood Basalt Provinces (CFBPs) are large igneous features formed by the extrusion of massive amounts of lavas that require significant evolution within the lithosphere. Although sequential lava flows are effective probes of magmatic systems, CFBPs are typically poorly preserved. We focus on lava flows from the well-preserved 1.1 Ga Keweenawan CFBP that erupted within the Midcontinent Rift System. We present a new geochemical, petrographic, and stratigraphic synthesis from the Main stage Portage Lake Volcanics (PLV). Flow-by-flow analysis of the PLV reveals that major element behavior is decoupled from trace element behavior; MgO exhibits limited variability, while compatible and incompatible trace elements deviate from high to low concentrations throughout the sequence. The concentrations of incompatible trace elements slightly decrease from the base of the sequence to the top. We investigate these observations by applying a recharge, evacuation, assimilation, and fractional crystallization model to geochemical and petrographic data. Our modelling demonstrates a magmatic system experiencing increased evacuation rates while fractionation and assimilation rates decrease, indicating an increase in magmatic flux. The outcome of this modelling is a progressively more efficient magma system within the PLV. This study highlights the utility of joint petrographic and geochemical interpretation in constraining CFBP magma evolution.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5424758

Initial Cenozoic Magmatic Activity in East Africa: New Geochemical Constraints on Magma Distribution within the Eocene Continental Flood Basalt Province

2021 ◽  
pp. SP518-2020-262
Author(s):  
R. Alex Steiner ◽  
Tyrone O. Rooney ◽  
Guillaume Girard ◽  
Nick Rogers ◽  
Cynthia Ebinger ◽  
...  
Keyword(s):  
Shear Velocity ◽  
Flood Basalt ◽  
Main Phase ◽  
Large Igneous Province ◽  
Southern Ethiopia ◽  
East African ◽  
Continental Flood Basalt ◽  
Content Type ◽  
Supplementary Material ◽  
African Rift

AbstractThe initial interaction between material rising from the African Large Low Shear Velocity Province and the African lithosphere manifests as the Eocene continental large igneous province (LIP), centered on southern Ethiopia and northern Kenya. Here we present a geographically well-distributed geochemical dataset comprising the flood basalt lavas of the Eocene continental LIP to refine the regional volcano-stratigraphy into three distinct magmatic units: (1) the highly-alkaline small-volume Akobo Basalts (49.4–46.6 Ma), representing the initial phase of flood basalt volcanism derived from the melting of lithospheric-mantle metasomes, (2) the primitive and spatially restricted Amaro Basalts (45.2–39.58 Ma) representing the early main phase of flood basalt volcanism derived from the melting of the upwelling thermochemical anomaly, and (3) the spatially extensive Gamo-Makonnen magmatic unit (38-28 Ma) representing the mature main phase of flood basalt volcanism that has undergone significant processing within the lithosphere resulting in relatively homogeneous compositions. The focused intrusion of these main phase magmas over 10 m.y. preconditioned the African lithosphere for the localization of strain during subsequent episodes of lithospheric stretching. The focusing of strain into the region occupied by this continental LIP may have contributed to the initial extension in SW Ethiopia associated with the East African Rift.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5557626

Rifting in SW China: structural and sedimentary investigation of the initial crustal response to emplacement of the Permian Emeishan LIP

2018 ◽  
Vol 156 (4) ◽  
pp. 745-758 ◽  
Author(s):  
YU WANG ◽  
INGRID UKSTINS PEATE ◽  
ZHAOHUA LUO ◽  
SHUZHI WANG ◽  
LILU CHENG ◽  
...  
Keyword(s):  
Near Field ◽  
Flood Basalt ◽  
Large Igneous Province ◽  
Normal Faults ◽  
Rift System ◽  
Main Stage ◽  
Plate Motions ◽  
Sedimentary Deposits ◽  
Icp Ms ◽  
Clastic Sedimentary

AbstractDetailed structural, volcanic, and sedimentary investigations of the crustal response to the emplacement of the Middle–Late Permian Emeishan large igneous province show that a rifting system developed prior to the main stage of flood basalt eruptions, in the form of sedimentary breccias, clastic sedimentary deposits and mafic hydromagmatic units. Detrital zircon grains from sandstones yield ~750–800 Ma LA-ICP-MS 206Pb/238U age clusters, showing that material was sourced from the Yangtze crystalline basement. Gabbros and pegmatites intruded along the normal faults of the rift system yield zircon ages of 264–260 Ma, and thus constrain the timing of rifting. N–S-trending rift zones developed along the western flank of the Pan-Xi palaeo-uplift, with NE–SW- and NNE–SSW-trending rifts on the eastern side and along the western and eastern margins of the Yangtze Block. The rifting progressed in pulses, with an initial phase of normal faulting followed by rapid deposition of breccias. Later there was lower-energy deposition of sandstone, with accompanying rhyolitic eruptions. This was followed by low-energy sedimentation of mudstones and dolomites, with accompanying hydromagmatic deposits. Rift system formation was constrained by a combination of far- and near-field tectonic stresses due to plate motions and lithospheric interaction with initial Emeishan volcanism.

scholarly journals Evolution of a salt-rich transtensional rifted margin, eastern North Pyrenees, France

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2019-157 ◽  
Author(s):  
M. Ford ◽  
J. Vergés
Keyword(s):  
Sedimentary Cover ◽  
Google Earth ◽  
Rift System ◽  
Content Type ◽  
The North ◽  
Deep Faults ◽  
Supplementary Material ◽  
Uplift And Erosion ◽  
Rifted Margin ◽  
Early Late

In this field study we reinterpret the narrow eastern North Pyrenean Zone, France, as an inverted salt-rich transtensional rift system based on identification of halokinetic depositional sequences across rift platform to distal rift margin domains with a cumulative throw of >2.8 km on steep Cretaceous faults. The rift platform records extension on detached rotational faults above Triassic evaporites from Jurassic to Aptian with uplift and erosion during the Albian. Transtensional Aptian–Albian minibasins align along the salt-rich rift margin fault zone. In the Aptian–Albian main rift large en echelon synclinal minibasins developed between salt walls, although Jurassic diapiric evolution is likely. Upper Cretaceous units locally record continuing diapirism. The Boucheville and Bas Agly depocentres, altered by synrift HT metamorphism, form the distal rift domain terminating south against the North Pyrenean Fault. The narrowness of the Pyrenean rift, shape of minibasins, en echelon oblique synclinal depocentres and folds coupled with a discontinuous distribution and intensity of HT metamorphism support a transtensional regime along the Iberia–Europe plate margin during late Early and early Late Cretaceous. In this model, the distal European margin comprises deep faults limiting laterally discontinuous crustal domains and ‘hot’ pull-apart basins with mantle rocks directly beneath sedimentary cover.Supplementary material: A table summarizing the stratigraphy of the NE Pyrenees and an interpreted Google Earth view of the Quillan syncline and minibasin are available at https://doi.org/10.6084/m9.figshare.c.5100036

scholarly journals Thickness Characteristics of Pāhoehoe Lavas in the Deccan Province, Western Ghats, India, and in Continental Flood Basalt Provinces Elsewhere

2021 ◽  
Vol 8 ◽  
Author(s):  
Stephen Self ◽  
Tushar Mittal ◽  
Anne Elizabeth Jay
Keyword(s):  
Columbia River ◽  
Flood Basalt ◽  
Flow Fields ◽  
Lava Flows ◽  
Basalt Lava ◽  
Continental Flood Basalt ◽  
Quantitative Basis ◽  
Simple Flows ◽  
Lava Morphology ◽  
Central Atlantic

Constraining the eruption rates of flood basalt lava flows remains a significant challenge despite decades of work. One potential observable proxy for eruption rates is flood basalt lava-flow lobe thicknesses, a topic that we tackle here quantitatively. In this study, we provide the first global compilation of pāhoehoe lava-lobe thicknesses from various continental flood basalt provinces (∼ 3,800 measurements) to compare characteristic thicknesses within and between provinces. We refer to thin lobes (∼ ≤5 m), characteristic of “compound” lavas, as hummocky pāhoehoe lava flows or flow-fields. Conversely, we term thicker lobes, characteristic of “simple” flows, as coming from sheet-lobe-dominated flows. Data from the Deccan Traps and Columbia River flood-basalt provinces are archetypal since they have the most consistent datasets as well as established chemo- and litho-stratigraphies. Examining Deccan lobe thicknesses, we find that previously suggested (and disputed) distinct temporal and regional distributions of hummocky pāhoehoe and sheet-lobe-dominated flow fields are not strongly supported by the data and that each geochemically defined formation displays both lobe types in varying amounts. Thin flow-lobes do not appear to indicate proximity to source. The modal lobe thickness of Deccan formations with abundant “thin” lava-lobes is 8 m, while the mode for sheet-lobe-dominated formations is only 17 m. Sheet-lobes up to 75–80 m are rare in the Deccan and Columbia River Provinces, and ones >100 m are exceptional globally. For other flood basalt provinces, modal thickness plots show a prevalence toward similar lobe thicknesses to Deccan, with many provinces having some or most lobes in the 5–8 m modal range. However, median values are generally thicker, in the 8–12 m range, suggesting that sheet-lobes dominate. By contrast, lobes from non-flood basalt flow-fields (e.g., Hawai’i, Snake River Plain) show distinctly thinner modes, sub-5 m. Our results provide a quantitative basis to ascertain variations in gross lava morphology and, perhaps, this will in future be related to emplacement dynamics of different flood basalt provinces, or parts thereof. We can also systematically distinguish outlier lobes (or regions) from typical lobes in a province, e.g., North American Central Atlantic Magmatic Province lava-lobes are anomalously thick and are closely related to feeder-intrusions, thus enabling a better understanding of conditions required to produce large-volume, thick, flood basalt lava-lobes and flows.

The effects of basaltic lava flows on the petrophysical properties and diagenesis of interbedded aeolian sandstones: an example from the Cretaceous Paraná Basin, Brazil

2020 ◽  
pp. petgeo2020-036
Author(s):  
G. Bertolini ◽  
A.J. Hartley ◽  
J.C. Marques ◽  
D. Healy ◽  
J.C. Frantz
Keyword(s):  
Lava Flows ◽  
P Wave ◽  
Basaltic Lava ◽  
Petrophysical Properties ◽  
Reservoir Properties ◽  
Content Type ◽  
Paraná Basin ◽  
Supplementary Material ◽  
Parana Basin ◽  
Type 3

An analysis of the petrophysical and diagenetic effects of the emplacement of Cretaceous basaltic lava flows (Serra Geral Formation) on aeolian sandstones (Botucatu Formation) has been undertaken on core samples from the Paraná Basin, Brazil. Between 0.1 to 1 m from the contact zone, acoustic wave velocities and porosities in sandstones show a significantly wider scatter than those located >1m away from the lava contact. Higher P-wave values (av. 3759.3 ms-1) occur between 0.1 to 1 m from the lava contact in contrast to those areas > 1 m away (av. 3376.8 ms-1), whilst the average porosity is 6.5% near the contact (0.1 to 1 m), and 10.7% away from the contact (>1 m). Petrographic evaluation reveals two diagenetic pathways responsible for modification of the petrophysical properties: early hydrothermal Mg-rich authigenesis (Type 1) and early chemical dissolution (Type 2). Type 3 diagenesis occurs away from the lava-sediment contact (>1 m) with the appearance of poikilitic calcite and smectite. The sandstone samples associated with Types 1 and 2 diagenesis display a decrease in porosity and increased acoustic velocities in relation to Type 3, while Type 3 samples show little or no variation in reservoir properties. The lava-induced diagenetic effects at the sandstone-lava contacts (0.1 to 1 m) may form a baffle or seal to fluids around the margins of the sandstone bodies. Therefore, whilst diagenesis associated with lava emplacement may hinder reservoir quality around the margins, the original reservoir properties are preserved within these large sandstone bodies.Supplementary material: Petrophysical and petrographic data is available as annex files. https://doi.org/10.6084/m9.figshare.c.5244473

Rapid changes from arid to humid conditions during the onset of the Paraná-Etendeka Igneous Provinces: Can volcanic gas emissions from Continental Flood Basalts affect the precipitation regime?

2021 ◽  
pp. SP520-2020-176
Author(s):  
V. G. P. Cruz ◽  
E. F. Lima ◽  
L. M. M. Rossetti ◽  
N. G. Pasqualon
Keyword(s):  
Flood Basalt ◽  
Surface Cooling ◽  
Precipitation Regime ◽  
Volcanic Gas ◽  
Flood Basalts ◽  
Content Type ◽  
Continental Flood Basalts ◽  
Igneous Province ◽  
Volcaniclastic Rocks ◽  
Supplementary Material

AbstractDespite the intriguing correlation between Continental Flood Basalts (CFB) provinces and environmental crises, little is known about how the local/regional sedimentary systems and environment respond to flood basalt volcanism. Active sedimentary systems, and their interaction with volcanism, provides an important rock record to understand palaeoenvironments in volcanic settings. The Paraná-Etendeka Igneous Province is a well-known example of a CFB emplaced on a dry desert environment, but evidence has also shown the existence of humid conditions during the volcanic episode. This work describes and interprets non-volcanic sedimentary and volcaniclastic rocks interbedded with Paraná-Etendeka Igneous Province lavas in southernmost Brazil to better understand palaeoenvironmental process and changes during the onset of volcanism. Non-volcanic sedimentary rocks record the existence of ephemeral sheet-like flows and ponds/lakes while volcaniclastic rocks documents hydromagmatic activity, supporting a change to more humid conditions. Stratigraphic constrains indicate that this change started with the onset of volcanism and affected the whole province. We suggest that SO2 degassing from Paraná-Etendeka province may have caused a net global surface cooling resulting in precipitation redistribution and a local increase in rainfall. This hypothesis may help explaining the cooling and increased humidity observed elsewhere to be closely related with the Paraná-Etendeka emplacement.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5505710

scholarly journals Marie Byrd Land lithospheric mantle: A review of the xenolith record

2021 ◽  
pp. M56-2020-17
Author(s):  
Monica R. Handler ◽  
Richard J. Wysoczanski ◽  
John A. Gamble
Keyword(s):  
Lithospheric Mantle ◽  
Rift System ◽  
Type I ◽  
Content Type ◽  
Partial Melt ◽  
West Antarctic ◽  
Supplementary Material ◽  
Geochemical Analyses ◽  
West Antarctic Rift System ◽  
West Antarctic Rift

AbstractThe Marie Byrd Land (MBL) lithospheric mantle xenolith record comprises over 100 samples from a range of localities spanning both major crustal terranes that comprise MBL: Ross and Amundsen provinces. Coarse granular to porphyroclastic in texture, the xenoliths are predominantly Type I spinel-bearing lherzolites to harburgites, but include rare dunite and pyroxenite examples. Garnet is absent and no hydrous phases, such as amphibole or mica, have been reported to date, although traces of apatite may be present. Characterisation of the lithospheric mantle composition and its evolution however, is hampered by patchy and uneven geochemical analyses across the xenolith suite. Nonetheless, a picture emerges of a heterogeneous lithosphere beneath both Ross and Amundsen Provinces. Previously published and new data reported here are consistent with samples ranging from variably cryptically metasomatised residua from variable (10 - 25%) degrees of partial melt extraction to refertilised compositions. Limited isotopic data point to a complex history, providing evidence for both ancient Proterozoic lithospheric mantle and preservation of Ordovician events. The Sr-Nd-Pb composition of the sampled lithospheric mantle overlaps the common low-µ isotopic endmember identified in Cenozoic magmatism from MBL and the wider West Antarctic Rift System.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5309814

Volcano-sedimentary processes at Las Derrumbadas rhyolitic twin domes, Serdán-Oriental basin, Eastern Trans-Mexican Volcanic Belt

2021 ◽  
pp. SP520-2021-144
Author(s):  
Marie-Noëlle Guilbaud ◽  
Corentin Chédeville ◽  
Ángel Nahir Molina-Guadarrama ◽  
Julio Cesar Pineda-Serrano ◽  
Claus Siebe
Keyword(s):  
Volcanic Belt ◽  
Debris Avalanche ◽  
Density Currents ◽  
Content Type ◽  
Mexican Volcanic Belt ◽  
Wide Range ◽  
Eruptive Episode ◽  
Basin Floor ◽  
Supplementary Material ◽  
Trans Mexican Volcanic Belt

AbstractThe eruption of the ∼10 km3 rhyolitic Las Derrumbadas twin domes about 2000 yrs ago has generated a wide range of volcano-sedimentary deposits in the Serdán-Oriental lacustrine basin, Trans-Mexican Volcanic Belt. Some of these deposits have been quarried, creating excellent exposures. In this paper we describe the domes and related products and interpret their mode of formation, reconstructing the main phases of the eruption as well as syn-and-post eruptive erosional processes. After an initial phreatomagmatic phase that built a tuff ring, the domes grew as an upheaved plug lifting a thick sedimentary pile from the basin floor. During uplift, the domes collapsed repeatedly to form a first-generation of hetero-lithologic hummocky debris avalanche deposits. Subsequent dome growth produced a thick talus and pyroclastic density currents. Later, the hydrothermally-altered over-steepened dome peaks fell to generate 2nd generation, mono-lithologic avalanches. Subsequently, small domes grew in the collapse scars. From the end of the main eruptive episode onwards, heavy rains remobilized parts of the dome carapaces and talus, depositing lahar aprons. Las Derrumbadas domes are still an important source of sediments in the basin, and ongoing mass-wasting processes are associated with hazards that should be assessed, given their potential impact on nearby populations.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5752296

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