scholarly journals Longevity of the Permian Emeishan mantle plume (SW China): 1 Ma, 8 Ma or 18 Ma?

2008 ◽  
Vol 145 (3) ◽  
pp. 373-388 ◽  
Author(s):  
J. GREGORY SHELLNUTT ◽  
MEI-FU ZHOU ◽  
DAN-PING YAN ◽  
YANBIN WANG
Keyword(s):  
Trace Element ◽  
Flood Basalt ◽  
Large Igneous Province ◽  
Flood Basalts ◽  
Geological Evidence ◽  
Ocean Island Basalts ◽  
Igneous Province ◽  
Emeishan Mantle Plume ◽  
Decompressional Melting ◽  
Shrimp Zircon

AbstractAfter the formation of the ~ 260 Ma Emeishan large igneous province, there were two volumetrically minor magmatic pulses at ~ 252 Ma and ~ 242 Ma, respectively. Alkaline mafic dykes intruding both 260 Ma and 252 Ma felsic plutons in the Panxi region, southwestern China, have compositions similar to the Emeishan flood basalts. One dyke is dated using the SHRIMP zircon U–Pb technique at 242 ± 2 Ma, ~ 18 Ma younger than the start of Emeishan magmatism. The dykes have enriched light rare earth element patterns (La/YbN = 4.4–18.8) and trace element patterns similar to the Emeishan flood basalts and average ocean-island basalts. Some trace element ratios of the dykes (Zr/Nb = 3.8–8.2, La/Nb = 0.4–1.7, Ba/La = 7.5–25.6) are somewhat similar to EM1 source material, however, there are differences. Their εNd values (εNd = +2.6 and +2.7) andISr (ISr = 0.704542 and 0.704554) ratios are indicative of a mantle source. Thus Emeishan magmatism may have lasted for almost 20 Ma after the initial eruption. However, geological evidence precludes the possibility that the post-260 Ma magmatic events were directly related to Emeishan magmatism, which began at and ended shortly after 260 Ma. The 252 Ma plutons and 242 Ma dykes represent volumetrically minor melting of the fossil Emeishan plume-head beneath the Yangtze crust. The 252 Ma magmatic event was likely caused by post-flood basalt extension of the Yangtze crust, whereas the 242 Ma event was caused by decompressional melting associated with the collision between the South China and North China blocks during the Middle Triassic.

scholarly journals Geology of the Mesoproterozoic Pillar Lake Volcanics and Inspiration Sill, Armstrong, Ontario: Evidence of Early Midcontinent Rift Magmatism in the Northwestern Nipigon Embayment

2021 ◽  
Author(s):  
Pete Hollings ◽  
Mark Smyk ◽  
Wouter Bleeker ◽  
Michael A. Hamilton ◽  
Robert Cundari ◽  
...  
Keyword(s):  
North America ◽  
Direct Contact ◽  
Large Igneous Province ◽  
Rift System ◽  
Flood Basalts ◽  
Midcontinent Rift ◽  
Igneous Province ◽  
Intrusive Rocks ◽  
Midcontinent Rift System ◽  
Northern Edge

The Midcontinent Rift System of North America is a ~1.1 Ga large igneous province comprising mainly flood basalts and intrusive rocks. We present new data for the Pillar Lake Volcanics and Inspiration Sill from the northern edge of the Midcontinent Rift in the northwestern Nipigon Embayment. The Pillar Lake Volcanics comprise a ~20-40 m-thick, flat-lying sequence of mafic pillowed and massive flows, pillowed flow breccia, and hyaloclastite breccia. They are characterized by SiO2 of 52-54 wt%, TiO2 of 1.2 to 1.3 wt% and K2O of 0.9 to 1.1 wt%. They are LREE-enriched, with La/Smn of 3.0 to 4.4 with fractionated HREE (Gd/Ybn = 1.4 to 1.7). The Inspiration diabase sill is < 50 m thick and is in direct contact with the underlying Pillar Lake Volcanics. Baddeleyite and zircon data from the Inspiration Sill yield a combined U-Pb upper intercept age of 1105.6 ± 1.6 Ma. The Inspiration Sill is characterized by uniform SiO2 of 52 to 53 wt%, TiO2 of 1.1 to 1.2 and K2O of 0.9 to 1.2 wt%. Inspiration Sill samples are LREE enriched with La/Smn of 3.2 to 3.3 and fractionated HREE of (Gd/Ybn = 1.6). The Pillar Lake Volcanics are at least 1120 Ma, and perhaps as old as 1130 Ma and represent an early, thin, and restricted mafic volcanic sequence, largely preserved below the younger Inspiration Sill. The Pillar Lake Volcanics and Inspiration Sill display a marked geochemical similarity, suggesting that they may represent magmatism associated with the earliest stages of Midcontinent rifting.

Spatial variability in Karoo dolerites

2021 ◽  
Author(s):  
Arnold Kotze ◽  
R. James Roberts
Keyword(s):  
South Africa ◽  
Trace Element ◽  
Basaltic Magma ◽  
Principal Component ◽  
Large Igneous Province ◽  
Appreciable Amount ◽  
Data Set ◽  
Igneous Province ◽  
Positive Loading ◽  
Project Data

&lt;p&gt;AD Kotze and RJ Roberts&lt;/p&gt;&lt;p&gt;Department of Geology, University of Pretoria, Hatfield, Pretoria, South Africa; [email protected]&lt;/p&gt;&lt;p&gt;The Karoo Large Igneous Province (KLIP) in South Africa consists of both a spatially limited extrusive basalt suite (Drakensberg Group) and a spatially extensive dolerite suite, both generally considered to be remarkable homogenous and of a &amp;#8220;low-Ti&amp;#8221; character (Luttinen, 2018). The homogeneity of the rocks requires that statistical analysis is necessary to look for spatial and geochemical trends in the data, which may yield clues to the mantle processes producing the 60 000 km&lt;sup&gt;2&lt;/sup&gt; expanse of basaltic magma. In this project, data derived from several locations are used as proxies to check for lateral variability in the Karoo dolerites. A principal component analysis (PCA) on trace element data using a covariance matrix was performed, and comparisons based on variables that are 1) common to the Karoo dolerites and Lesotho basalts and, 2) responsible for the most amount of variation to the data set are made. Trace element modelling is then used to test different mantle melting scenarios possibly responsible for the variation seen in the dolerites.&lt;/p&gt;&lt;p&gt;Principal component analyses revealed several trace elements are responsible for most of the variability in the dolerites. Cr and Ni has the strongest positive loading on Component 1 whereas Cr and Ba has the strongest positive loading on Component 2. Ba has a strong negative loading on Component 1. Cu, Sr, V and Zr do impart an appreciable amount of variation to the data, but all four variables have weak negative loadings on both components. Interestingly, the activity of Cu and V seems to be the inverse of that of Cr and Ni.&lt;/p&gt;&lt;p&gt;Due to the nature of a PCA, this work is afforded an opportunity to place the geochemistry of the Karoo dolerites within a larger geodynamic context without bias. From the observed variation, the activity of Ba and Cr is interpreted as an assimilation-oxidation process, whereas the Ni signature reflects the mantle origin of the magmas. Further modelling of these processes will allow the testing of suggested mechanisms for the formation of the KLIP, especially whether the magmatism is plume-related or related to the foundering of crustal blocks.&lt;/p&gt;&lt;p&gt;Luttinen, A., 2018. Bilateral geochemical asymmetry in the Karoo large igneous province. Scientific Reports, 8(5223).&lt;/p&gt;

Were Karoo flood basalts derived from a LLSVP-related plume source?

2020 ◽  
Author(s):  
Arto Luttinen ◽  
Jussi Heinonen ◽  
Sanni Turunen ◽  
Richard Carlson ◽  
Mary Horan
Keyword(s):  
Oceanic Crust ◽  
Mantle Plume ◽  
Flood Basalt ◽  
Planetary Science ◽  
Large Igneous Province ◽  
Primitive Mantle ◽  
Geochemical Data ◽  
Flood Basalts ◽  
Depleted Mantle ◽  
Mantle Reservoir

&lt;p&gt;Examination of the least-contaminated rocks of the Jurassic Karoo flood basalt province indicates considerable compositional variability in the mantle source. New and previously published Sr, Nd, and Pb isotopic data are suggestive of two main categories of mantle reservoirs: one coincides with the field of depleted mantle (DM) -affinity oceanic crust and the other has low initial eNd (+3.3 to 0.3) and high &lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr (0.7039 to 0.7057) and &amp;#916;8/4 (92 to 138) typical of enriched mantle 1 (EM1) -affinity oceanic crust. Previous studies have proposed the DM type reservoir included domains affected by subduction-related fluids and recycled oceanic components (e.g. Heinonen et al., 2014). The EM1 type reservoir probably also contained subducted crustal components, but the geochemical data are suggestive of an additional primitive mantle (PM) type component (Turunen et al., 2019).&lt;/p&gt;&lt;p&gt;Importantly, the two reservoirs can be geochemically linked to a recently identified bilateral compositional asymmetry in the volumious Karoo flood basalts (Luttinen, 2018): The DM type&amp;#160; reservoir is the most likely source of Nb-depleted flood basalts in the southeastern Karoo subprovince (Lebombo rifted margin and Antarctica), whereas the EM1-PM type reservoir has been identified as the principal source of the Nb-undepleted flood basalts in the northwestern subprovince (Karoo-Kalahari-Zambezi basins). The boundary between the flood basalt subprovinces and the occurrences of the DM-affinity and EM1-PM-affinity rocks overlie the Jurassic location of the margin of the Jurassic sub-African LLSVP. Magmas derived from the EM1-PM type reservoir were largely emplaced above the deep mantle anomaly, whereas those derived from the DM type reservoir were emplaced outside the footprint of the LLSVP.&lt;/p&gt;&lt;p&gt;Based on isotopic similarity, the EM1-PM type reservoir of the Karoo province may record the same overall LLSVP material as the Gough component in the zoned Tristan da Cunha plume (e.g. Hoernle et al., 2015). Furthermore, it is possible that the DM type reservoir of the Karoo province, which has been interpreted to represent depleted upper mantle heated by mantle plume, could also represent a plume component and that the bilateral Karoo flood basalt province as a whole could thus register melting of a large zoned plume source associated with the margin of the sub-African LLSVP.&lt;/p&gt;&lt;p&gt;References&lt;/p&gt;&lt;p&gt;Heinonen, J.S., Carlson, R.W., Riley, T.R., Luttinen, A.V., Horan, M.F. (2014). Subduction-modi&amp;#64257;ed oceanic crust mixed with a depleted mantle reservoir in the sources of the Karoo continental &amp;#64258;ood basalt province. Earth and Planetary Science Letters 394, 229&amp;#8211;241. http://dx.doi.org/10.1016/j.epsl.2014.03.012&lt;/p&gt;&lt;p&gt;Hoernl, K., Ronde, J., Hauff, F., Garbe-Sch&amp;#246;nberg, D., Homrighausen, S., Werner, W., Morgan, J.P. (2015). &amp;#160;How and when plume zonation appeared during the 132 Myr evolution of the Tristan Hotspot. Nature Communications 6:7799. doi: 10.1038/ncomms8799&lt;/p&gt;&lt;p&gt;Luttinen, A.V. (2018). Bilateral geochemical asymmetry in the Karoo large igneous province. Scientific Reports 8:5223. doi:10.1038/s41598-018-23661-3&lt;/p&gt;&lt;p&gt;Turunen, S.T., Luttinen, A.V., Heinonen, J.S., Jamal, D.L. (2019). Luenha picrites, Central Mozambique &amp;#8211; Messengers from a mantle plume source of Karoo continental &amp;#64258;ood basalts? Lithos 346&amp;#8211;347. https://doi.org/10.1016/j.lithos.2019.105152&lt;/p&gt;

Erratum to “Flood basalt-related Fe–Ti oxide deposits in the Emeishan large igneous province, SW China” [Lithos 119 (2010) 123–136]

Lithos ◽  
2013 ◽  
Vol 162-163 ◽  
pp. 331
Author(s):  
Kwan-Nang Pang ◽  
Mei-Fu Zhou ◽  
Liang Qi ◽  
Gregory Shellnutt ◽  
Christina Yan Wang ◽  
...  
Keyword(s):  
Flood Basalt ◽  
Large Igneous Province ◽  
Sw China ◽  
Emeishan Large Igneous Province ◽  
Igneous Province

scholarly journals Simultaneous Quantification of Forsterite Content and Minor–Trace Elements in Olivine by LA–ICP–MS and Geological Applications in Emeishan Large Igneous Province

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 634
Author(s):  
Shitou Wu ◽  
Yadong Wu ◽  
Yueheng Yang ◽  
Hao Wang ◽  
Chao Huang ◽  
...  
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Inductively Coupled Plasma ◽  
Large Igneous Province ◽  
Emeishan Large Igneous Province ◽  
Inductively Coupled ◽  
Minor Elements ◽  
Icp Ms ◽  
Igneous Province ◽  
Peridotitic Mantle

Olivine forsterite contents [Fo = 100 × Mg/(Mg + Fe) in mol%] and minor–trace element concentrations can aid our understanding of the Earth’s mantle. Traditionally, these data are obtained by electron probe microanalysis for Fo contents and minor elements, and then by laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) for trace elements. In this study, we demonstrate that LA–ICP–MS, with a simplified 100% quantification approach, allows the calculation of Fo contents simultaneously with minor–trace elements. The approach proceeds as follows: (1) calculation of Fo contents from measured Fe/Mg ratios; (2) according to the olivine stoichiometric formula [(Mg, Fe)2SiO4] and known Fo contents, contents of Mg, Fe and Si can be computed, which are used as internal standards for minor–trace element quantification. The Fo content of the MongOLSh 11-2 olivine reference material is 89.55 ± 0.15 (2 s; N = 120), which agrees with the recommended values of 89.53 ± 0.05 (2 s). For minor–trace elements, the results matched well with the recommended values, apart from P and Zn data. This technique was applied to olivine phenocrysts in the Lijiang picrites from the Emeishan large igneous province. The olivine compositions suggest that the Lijiang picrites have a peridotitic mantle source.

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