scholarly journals Deep Carbon and the Life Cycle of Large Igneous Provinces

Elements ◽  
2019 ◽  
Vol 15 (5) ◽  
pp. 319-324 ◽  
Author(s):  
Benjamin A. Black ◽  
Sally A. Gibson
Keyword(s):  
Life Cycle ◽  
Plate Boundary ◽  
Flood Basalts ◽  
Relative Significance ◽  
Large Igneous Provinces ◽  
Igneous Provinces ◽  
Alkaline Magmas ◽  
Low Volume ◽  
Potential Carbon

Carbon is central to the formation and environmental impact of large igneous provinces (LIPs). These vast magmatic events occur over geologically short timescales and include voluminous flood basalts, along with silicic and low-volume alkaline magmas. Surface outgassing of CO2 from flood basalts may average up to 3,000 Mt per year during LIP emplacement and is subsidized by fractionating magmas deep in the crust. The large quantities of carbon mobilized in LIPs may be sourced from the convecting mantle, lithospheric mantle and crust. The relative significance of each potential carbon source is poorly known and probably varies between LIPs. Because LIPs draw on mantle reservoirs typically untapped during plate boundary magmatism, they are integral to Earth's long-term carbon cycle.

The life cycle of large igneous provinces

2021 ◽  
Author(s):  
Benjamin A. Black ◽  
Leif Karlstrom ◽  
Tamsin A. Mather
Keyword(s):  
Life Cycle ◽  
Large Igneous Provinces ◽  
Igneous Provinces

Supercontinents: myths, mysteries, and milestones

2018 ◽  
Vol 470 (1) ◽  
pp. 39-64 ◽  
Author(s):  
Daniel Pastor-Galán ◽  
R. Damian Nance ◽  
J. Brendan Murphy ◽  
Christopher J. Spencer
Keyword(s):  
Global Climate ◽  
Outer Core ◽  
Biogeochemical Cycles ◽  
Mantle Dynamics ◽  
Large Igneous Provinces ◽  
Igneous Provinces ◽  
Core Dynamics ◽  
Tectonically Active ◽  
Supercontinent Cycle

AbstractThere is an emerging consensus that Earth's landmasses amalgamate quasi-periodically into supercontinents, interpreted to be rigid super-plates essentially lacking tectonically active inner boundaries and showing little internal lithosphere–mantle interactions. The formation and disruption of supercontinents have been linked to changes in sea-level, biogeochemical cycles, global climate change, continental margin sedimentation, large igneous provinces, deep mantle circulation, outer core dynamics and Earth's magnetic field. If these hypotheses are correct, long-term mantle dynamics and much of the geological record, including the distribution of natural resources, may be largely controlled by these cycles. Despite their potential importance, however, many of these proposed links are, to date, permissive rather than proven. Sufficient data are not yet available to verify or fully understand the implications of the supercontinent cycle. Recent advances in many fields of geoscience provide clear directions for investigating the supercontinent cycle hypothesis and its corollaries but they need to be vigorously pursued if these far-reaching ideas are to be substantiated.

scholarly journals Neoarchean large igneous provinces on the Kaapvaal Craton in southern Africa re-define the formation of the Ventersdorp Supergroup and its temporal equivalents

2020 ◽  
Vol 132 (9-10) ◽  
pp. 1829-1844 ◽  
Author(s):  
Ashley Gumsley ◽  
Joaen Stamsnijder ◽  
Emilie Larsson ◽  
Ulf Söderlund ◽  
Tomas Naeraa ◽  
...  
Keyword(s):  
Mantle Plume ◽  
Southern Africa ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Kaapvaal Craton ◽  
Ionization Mass ◽  
Flood Basalts ◽  
Large Igneous Provinces ◽  
Igneous Provinces ◽  
World Class

Abstract U-Pb geochronology on baddeleyite is a powerful technique that can be applied effectively to chronostratigraphy. In southern Africa, the Kaapvaal Craton hosts a well-preserved Mesoarchean to Paleoproterozoic geological record, including the Neoarchean Ventersdorp Supergroup. It overlies the Witwatersrand Supergroup and its world-class gold deposits. The Ventersdorp Supergroup comprises the Klipriviersberg Group, Platberg Group, and Pniel Group. However, the exact timing of formation of the Ventersdorp Supergroup is controversial. Here we present 2789 ± 4 Ma and 2787 ± 2 Ma U-Pb isotope dilution-thermal ionization mass spectrometry (ID-TIMS) baddeleyite ages and geochemistry on mafic sills intruding the Witwatersrand Supergroup, and we interpret these sills as feeders to the overlying Klipriviersberg Group flood basalts. This constrains the age of the Witwatersrand Supergroup and gold mineralization to at least ca. 2.79 Ga. We also report 2729 ± 5 Ma and 2724 ± 7 Ma U-Pb ID-TIMS baddeleyite ages and geochemistry from a mafic sill intruding the Pongola Supergroup and on an east-northeast–trending mafic dike, respectively. These new ages distinguish two of the Ventersdorp Supergroup magmatic events: the Klipriviersberg and Platberg. The Ventersdorp Supergroup can now be shown to initiate and terminate with two large igneous provinces (LIPs), the Klipriviersberg and Allanridge, which are separated by Platberg volcanism and sedimentation. The age of the Klipriviersberg LIP is 2791–2779 Ma, and Platberg volcanism occurred at 2754–2709 Ma. The Allanridge LIP occurred between 2709–2683 Ma. Klipriviersberg, Platberg, and Allanridge magmatism may be genetically related to mantle plume(s). Higher heat flow and crustal melting resulted as a mantle plume impinged below the Kaapvaal Craton lithosphere, and this was associated with rifting and the formation of LIPs.

Life-Cycle Cost Analysis of a Low-Volume Road Bridge Alternative

2000 ◽  
Vol 1696 (1) ◽  
pp. 8-13 ◽  
Author(s):  
M. E. Fagen ◽  
B. M. Phares
Keyword(s):  
Life Cycle ◽  
Cost Analysis ◽  
Life Cycle Cost ◽  
Primary Objective ◽  
Steel Beams ◽  
Steel Beam ◽  
Life Cycle Cost Analysis ◽  
Cost Models ◽  
Low Volume

Life-cycle cost models offer engineers a means to evaluate the anticipated long-term economic performance of prospective design and construction alternatives. Traditionally, only initial investment costs and past experience were used to economically evaluate possible bridge designs. A more logical approach requires that all short- and long-term costs be considered in relation to project location, purpose, and performance specifications. The primary objective of life-cycle cost analysis is to evaluate the total ownership cost of all suitable alternatives. Recent reports indicate that a significant number of the nation’s bridges are either structurally deficient or functionally obsolete. In Iowa, a large portion of these types of bridges are on the secondary road system and fall under the jurisdiction of county engineers. Typically, Iowa county engineers have limited resources. In response to this, a bridge-replacement system was developed that county engineers can design and build with limited staff. The system, which is made up of precast (PC) double T units, involves the fabrication of PC units that consist of two steel beams connected by a thin concrete deck. To illustrate that this bridge system may be an economically viable bridge-replacement alternative for use on low-volume county roads, a life-cycle cost analysis was completed for an actual replacement-repair-rehabilitation project. Various alternatives were economically analyzed and compared with the steel beam PC unit bridge alternative. This analysis indicates that, when lower-cost salvaged steel beams and county work forces are used, the steel beam PC unit bridge can be a viable low-volume road bridge alternative.

scholarly journals Volcanic controls on seawater sulfate over the past 120 million years

2020 ◽  
Vol 117 (35) ◽  
pp. 21118-21124 ◽  
Author(s):  
Thomas A. Laakso ◽  
Anna Waldeck ◽  
Francis A. Macdonald ◽  
David Johnston
Keyword(s):  
Isotope Effects ◽  
Sedimentary Basins ◽  
Sulfur Cycle ◽  
Marine Ecology ◽  
Large Igneous Provinces ◽  
Seawater Sulfate ◽  
Igneous Provinces ◽  
Abrupt Changes ◽  
Isotope Record

Changes in the geological sulfur cycle are inferred from the sulfur isotopic composition of marine barite. The structure of the34S/32S record from the Mesozoic to present, which includes ∼50- and 100-Ma stepwise increases, has been interpreted as the result of microbial isotope effects or abrupt changes to tectonics and associated pyrite burial. Untangling the physical processes that govern the marine sulfur cycle and associated isotopic change is critical to understanding how climate, atmospheric oxygenation, and marine ecology have coevolved over geologic time. Here we demonstrate that the sulfur outgassing associated with emplacement of large igneous provinces can produce the apparent stepwise jumps in the isotopic record when coupled to long-term changes in burial efficiency. The record of large igneous provinces map onto the required outgassing events in our model, with the two largest steps in the sulfur isotope record coinciding with the emplacement of large igneous provinces into volatile-rich sedimentary basins. This solution provides a quantitative picture of the last 120 My of change in the ocean’s largest oxidant reservoir.

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