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.

scholarly journals Up, down, or sideways: emplacement of magmatic Fe–Ni–Cu–PGE sulfide melts in large igneous provinces

2019 ◽  
Vol 56 (7) ◽  
pp. 756-773 ◽  
Author(s):  
C.M. Lesher
Keyword(s):  
Fluid Dynamic ◽  
Experimental Studies ◽  
Natural Systems ◽  
Large Igneous Provinces ◽  
Ultimate Explanation ◽  
Preferential Localization ◽  
Igneous Provinces ◽  
Sulfide Melt ◽  
Analog Systems ◽  
Almost All

The preferential localization of Fe–Ni–Cu–PGE sulfides within the horizontal components of dike–sill–lava flow complexes in large igneous provinces (LIPs) indicates that they were fluid dynamic traps for sulfide melts. Many authors have interpreted them to have collected sulfide droplets transported upwards, often from deeper “staging chambers”. Although fine (<1–2 cm) dilute (<10%–15%) suspensions of dense (∼4–5 g/cm3) sulfide melt can be transported in ascending magmas, there are several problems with upward-transport models for almost all LIP-related deposits: (1) S isotopic data are consistent with nearby crustal sources, (2) xenoliths appear to be derived from nearby rather than deeper crustal sources, (3) lateral sheet flow or sill facies of major deposits contain few if any sulfides, (4) except where there is evidence for a local S source, sulfides or chalcophile element enrichments rarely if ever occur in the volcanic components even where there is mineralization in the subvolcanic plumbing system, and (5) some lavas are mildly to strongly depleted in PGE >>> Cu > Ni > Co, indicating that unerupted sulfides sequestered PGEs at depth. Two potential solutions to this paradox are that (i) natural systems contained surfactants that lowered sulfide–silicate interfacial tensions, permitting sulfide melts to coalesce and settle more easily than predicted from theoretical/experimental studies of artificial/analog systems, and (or) (ii) sulfides existed not as uniformly dispersed droplets, as normally assumed, but as fluid-dynamically coherent pseudoslugs or pseudolayers that were large and dense enough that they could not be transported upwards. Regardless of the ultimate explanation, it seems likely that most high-grade Ni–Cu–PGE sulfide deposits in LIPs formed at or above the same stratigraphic levels as they are found.

Introduction to special issue on Large Igneous Provinces of Asia, Mantle Plumes and Metallogeny

2010 ◽  
Vol 51 (9) ◽  
pp. 899-902 ◽  
Author(s):  
N.L. Dobretsov ◽  
F. Pirajno ◽  
A.S. Borisenko ◽  
A.E. Izokh
Keyword(s):  
Mantle Plumes ◽  
Special Issue ◽  
Large Igneous Provinces ◽  
Igneous Provinces

scholarly journals Buoyant hydrous mantle plume from the mantle transition zone

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Takeshi Kuritani ◽  
Qun-Ke Xia ◽  
Jun-Ichi Kimura ◽  
Jia Liu ◽  
Kenji Shimizu ◽  
...  
Keyword(s):  
Transition Zone ◽  
Mantle Plume ◽  
Mantle Transition Zone

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.

Regional uplift associated with continental large igneous provinces: The roles of mantle plumes and the lithosphere

2007 ◽  
Vol 241 (3-4) ◽  
pp. 282-318 ◽  
Author(s):  
A.D. Saunders ◽  
S.M. Jones ◽  
L.A. Morgan ◽  
K.L. Pierce ◽  
M. Widdowson ◽  
...  
Keyword(s):  
Mantle Plumes ◽  
Large Igneous Provinces ◽  
Igneous Provinces

scholarly journals African cratonic lithosphere carved by mantle plumes

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Nicolas Luca Celli ◽  
Sergei Lebedev ◽  
Andrew J. Schaeffer ◽  
Carmen Gaina
Keyword(s):  
Seismic Tomography ◽  
Mantle Plumes ◽  
Large Igneous Provinces ◽  
Deep Mantle ◽  
Igneous Provinces ◽  
Waveform Tomography

AbstractHow cratons, the ancient cores of continents, evolved since their formation over 2.5 Ga ago is debated. Seismic tomography can map the thick lithosphere of cratons, but its resolution is low in sparsely sampled continents. Here we show, using waveform tomography with a large, newly available dataset, that cratonic lithosphere beneath Africa is more complex and fragmented than seen previously. Most known diamondiferous kimberlites, indicative of thick lithosphere at the time of eruption, are where the lithosphere is thin today, implying surprisingly widespread lithospheric erosion over the last 200 Ma. Large igneous provinces, attributed to deep-mantle plumes, were emplaced near all lithosphere-loss locations, concurrently with or preceding the loss. This suggests that the cratonic roots foundered once modified by mantle plumes. Our results imply that the total volume of cratonic lithosphere has decreased since its Archean formation, with the fate of each craton depending on its movements relative to plumes.

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.

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