Coupled supercontinent–mantle plume events evidenced by oceanic plume record

Geology ◽  
2019 ◽  
Vol 48 (2) ◽  
pp. 159-163 ◽  
Author(s):  
Luc S. Doucet ◽  
Zheng-Xiang Li ◽  
Richard E. Ernst ◽  
Uwe Kirscher ◽  
Hamed Gamal El Dien ◽  
...  
Keyword(s):  
Mantle Plume ◽  
Shear Velocity ◽  
Temporal Variations ◽  
Large Igneous Provinces ◽  
First Order ◽  
The Past ◽  
Igneous Provinces ◽  
Island Basalt ◽  
Supercontinent Cycle ◽  
Low Shear

Abstract The most dominant features in the present-day lower mantle are the two antipodal African and Pacific large low-shear-velocity provinces (LLSVPs). How and when these two structures formed, and whether they are fixed and long lived through Earth history or dynamic and linked to the supercontinent cycles, remain first-order geodynamic questions. Hotspots and large igneous provinces (LIPs) are mostly generated above LLSVPs, and it is widely accepted that the African LLSVP existed by at least ca. 200 Ma beneath the supercontinent Pangea. Whereas the continental LIP record has been used to decipher the spatial and temporal variations of plume activity under the continents, plume records of the oceanic realm before ca. 170 Ma are mostly missing due to oceanic subduction. Here, we present the first compilation of an Oceanic Large Igneous Provinces database (O-LIPdb), which represents the preserved oceanic LIP and oceanic island basalt occurrences preserved in ophiolites. Using this database, we are able to reconstruct and compare the record of mantle plume activity in both the continental and oceanic realms for the past 2 b.y., spanning three supercontinent cycles. Time-series analysis reveals hints of similar cyclicity of the plume activity in the continent and oceanic realms, both exhibiting a periodicity of ∼500 m.y. that is comparable to the supercontinent cycle, albeit with a slight phase delay. Our results argue for dynamic LLSVPs where the supercontinent cycle and global subduction geometry control the formation and locations of the plumes.

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.

How thermochemical piles initiate plumes at their edges

2020 ◽  
Author(s):  
Björn Heyn ◽  
Clinton Conrad ◽  
Reidar Trønnes
Keyword(s):  
Numerical Models ◽  
Shear Velocity ◽  
Viscous Drag ◽  
Mantle Flow ◽  
Core Mantle Boundary ◽  
The Core ◽  
Plate Velocity ◽  
Igneous Provinces ◽  
Suggested Link ◽  
Low Shear

<p>Deep-rooted mantle plumes are thought to originate from the margins of the Large Low Shear Velocity Provinces (LLSVPs) at the base of the mantle. Visible in seismic tomography, the LLSVPs are often numerically modeled as dense and viscous thermochemical piles. Although the piles force lateral mantle flow upwards at their edges, it is not clear if, and how, plumes are predominantly initiated at the pile margins. In this study, we develop numerical models that show a series of plumes periodically rising from the margin of an approximately 300 km thick dense thermochemical pile, with each plume temporarily increasing the pile’s local thickness to almost 370 km due to upward viscous drag from the rising plume. When the plume is pushed towards the pile center by the lateral mantle flow, the viscous drag on the dense material at the pile margin decreases and the pile starts to collapse back towards the core-mantle boundary (CMB). This causes the dense pile material to extend laterally along the CMB (about 150 km), locally thickening the lower thermal boundary layer on the CMB next to the pile, which initiates a new plume. The resulting plume cycle is reflected in both the thickness and lateral motion of the local pile margin within a few degrees of the pile edge, while the overall thickness of the pile is not affected. The frequency of plume generation is mainly controlled by the rate at which slab material is transported to the CMB, and thus depends on the plate velocity and the sinking rate of slabs in the lower mantle. Within Earth, this mechanism of episodic plume initiation may explain the suggested link between the positions of hotspots and Large Igneous Provinces (LIPs) and the LLSVP margins. Moreover, a collapse of the southeastern corner of the African LLSVP, and subsequent triggering of plumes around the spreading pile material, may explain the observed clustering of LIPs in that area between 95 and 155 Ma.</p>

scholarly journals Preliminary Appraisal of a Correlation Between Glaciations and Large Igneous Provinces Over the Past 720 Million Years

2020 ◽  
pp. 169-190
Author(s):  
Nasrrddine Youbi ◽  
Richard E. Ernst ◽  
Ross N. Mitchell ◽  
Moulay A. Boumehdi ◽  
Warda El Moume ◽  
...  
Keyword(s):  
Large Igneous Provinces ◽  
The Past ◽  
Igneous Provinces

Existence of the DHArwar-BAstar-SInghbhum (DHABASI) megacraton since 3.35 Ga: Constraints from the Precambrian Large Igneous Province record

2021 ◽  
pp. SP518-2021-53
Author(s):  
Rajesh K. Srivastava ◽  
Richard E. Ernst ◽  
Ulf Söderlund ◽  
Amiya K. Samal ◽  
Om Prakash Pandey ◽  
...  
Keyword(s):  
Building Block ◽  
Large Igneous Province ◽  
Indian Shield ◽  
Large Igneous Provinces ◽  
The Past ◽  
Igneous Provinces ◽  
Igneous Province ◽  
The Individual ◽  
Age Range

AbstractWe propose a Precambrian megacraton (consisting of two or more ancient cratons) ‘DHABASI’ in the Indian Shield that includes the Dharwar, Bastar and Singhbhum cratons. This interpretation is mainly based on seven large igneous provinces (LIPs) that are identified in these three cratons over the age range of ca. 3.35-1.77 Ga, a period of at least 1.6 Gyr. The absence of any subsequent breakup of ‘DHABASI’ since 1.77 Ga suggests that this megacraton has existed for the past 3.35 Gyr.In addition to their use in recognizing this megacraton, these LIP events may also provide likely targets for Cu-Ni-Cr-Co-PGE deposits. We suggest that the megacraton ‘DHABASI’ was an integral part of supercontinents/supercratons through Earth's history, and that it should be utilized as a distinct building block for paleocontinental reconstructions rather than using the individual Dharwar, Bastar and Singhbhum cratons.

scholarly journals Oceanic and super-deep continental diamonds share a transition zone origin and mantle plume transportation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Luc S. Doucet ◽  
Zheng-Xiang Li ◽  
Hamed Gamal El Dien
Keyword(s):  
Carbon Isotope ◽  
Transition Zone ◽  
Mantle Plume ◽  
Lithospheric Mantle ◽  
Mantle Plumes ◽  
Continental Lithosphere ◽  
Mantle Transition Zone ◽  
Large Igneous Provinces ◽  
Igneous Provinces ◽  
Almost All

AbstractRare oceanic diamonds are believed to have a mantle transition zone origin like super-deep continental diamonds. However, oceanic diamonds have a homogeneous and organic-like light carbon isotope signature (δ13C − 28 to − 20‰) instead of the extremely variable organic to lithospheric mantle signature of super-deep continental diamonds (δ13C − 25‰ to + 3.5‰). Here, we show that with rare exceptions, oceanic diamonds and the isotopically lighter cores of super-deep continental diamonds share a common organic δ13C composition reflecting carbon brought down to the transition zone by subduction, whereas the rims of such super-deep continental diamonds have the same δ13C as peridotitic diamonds from the lithospheric mantle. Like lithospheric continental diamonds, almost all the known occurrences of oceanic diamonds are linked to plume-induced large igneous provinces or ocean islands, suggesting a common connection to mantle plumes. We argue that mantle plumes bring the transition zone diamonds to shallower levels, where only those emplaced at the base of the continental lithosphere might grow rims with lithospheric mantle carbon isotope signatures.

Sign in / Sign up

Export Citation Format

Share Document