Os, Pb, and Nd isotope geochemistry of the Permian Emeishan continental flood basalts: Insights into the source of a large igneous province

2007 ◽  
Vol 71 (8) ◽  
pp. 2104-2119 ◽  
Author(s):  
Ji-Feng Xu ◽  
Katsuhiko Suzuki ◽  
Yi-Gang Xu ◽  
Hou-Jun Mei ◽  
Jie Li
Keyword(s):  
Isotope Geochemistry ◽  
Large Igneous Province ◽  
Flood Basalts ◽  
Nd Isotope ◽  
Continental Flood Basalts ◽  
Igneous Province

scholarly journals Late Permian High-Ti Basalt in Western Guangxi, SW China and Its Link With the Emeishan Large Igneous Province: Geochronological and Geochemical Perspectives

2021 ◽  
Vol 9 ◽  
Author(s):  
Chenguang Zhang ◽  
Renyu Zeng ◽  
Changming Li ◽  
Jian Jiang ◽  
Tianguo Wang ◽  
...  
Keyword(s):  
Weighted Average ◽  
Large Igneous Province ◽  
Late Permian ◽  
Flood Basalts ◽  
Sw China ◽  
Continental Flood Basalts ◽  
Emeishan Large Igneous Province ◽  
Igneous Province ◽  
The Difference ◽  
Emeishan Lip

High-Ti (Ti/Y) flood basalts are widely distributed in the Late Permian Emeishan large igneous province (LIP), SW China, and their spatial distribution and genetic mechanism are important to reveal the role of plume-lithosphere interactions in the LIP origin. Western Guangxi is located on the eastern edge of Emeishan LIP. To explore the genesis of the high-Ti basalt in western Guangxi and any genetic link with the Emeishan LIP, we performed whole-rock geochemical and Sr-Nd isotope and zircon U-Pb-Hf isotope analyses on the Longlin basalts from western Guangxi. The results indicate that the Longlin basalt from Tongdeng area has relatively high SiO2 but low MgO and TFe2O3 contents. The rocks have zircon εHf(t) = −0.42 to 6.41, whole-rock (87Sr/86Sr)i = 0.707167–0.707345, and εNd(t) = −2.5 to −2.14. In contrast, the Longlin basalt from Zhoudong area has relatively low SiO2 but high MgO and TFe2O3 contents. The rocks have whole-rock (87Sr/86Sr)i = 0.706181–0.706191 and εNd(t) = −0.57 to 0.69. Four Longlin basalt samples display LREE enrichments and HREE depletions, and with indistinct δEu and δCe anomalies. LA-ICP-MS zircon U-Pb dating on three Longlin basalt samples (from different localities) yielded consistent weighted average age of 257.9 ± 2.6 Ma (MSWD = 0.55), 259.5 ± 0.75 Ma (MSWD = 3.0), and 256.7 ± 2.0 Ma (MSWD = 0.68), indicating a Late Permian emplacement. Considering the similar age and geochemical features between the Longlin basalt and Emeishan flood basalts, we interpret that the former is spatially, and temporally associated with the Emeishan LIP. Geochemical features show that the high-Ti basalts in western Guangxi resemble Deccan-type continental flood basalts (CFBs), which were derived by decompression melting of the mantle plume. Combined with previous geochemical studies, we suggest that the difference in Ti content and Ti/Y ratio in CFBs are related to the depth and melting degree of mantle source, in which high-Ti features may have been linked to low degree of partial melting in the deep mantle.

scholarly journals Rapid eruption of the Emeishan continental flood basalts: New paleomagnetic and geochronologic constraints

2021 ◽  
Author(s):  
Yingchao Xu ◽  
Liandi Zheng ◽  
Zhenyu Yang ◽  
Ya-Bo Tong ◽  
Bin Wang ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Total Duration ◽  
Central Zone ◽  
Large Igneous Province ◽  
Reverse Polarity ◽  
Flood Basalts ◽  
Continental Flood Basalts ◽  
Emeishan Large Igneous Province ◽  
Igneous Province ◽  
Normal Polarity

The duration of the eruption of the Emeishan large igneous province is hotly debated. We conducted a magnetostratigraphic and geochronological study of the core area of the large igneous province in the Binchuan area of Yunnan Province, southwestern China, in order to constrain the duration of the eruption. The results of detailed thermal demagnetization experiments revealed two remanent magnetic components from the volcanic rocks of 11 composite sections. A low-temperature component separated below 300 °C is interpreted as a recent viscous remanence. Additionally, reliable characteristic remanent magnetizations were revealed above 400 °C, with unblocking temperatures up to 580−680 °C, which passed the fold test and record three magnetozones. Zircons from the felsic ignimbrites exposed in the final stage of the mafic volcanism are dated to 258.2 ± 0.7 Ma (n = 15; mean square of weighted deviates = 1.3) by sensitive high-resolution ion microprobe. Stratigraphic and magnetostratigraphic correlations of the Emeishan basalts in the Binchuan sections indicate that the eruption of the mafic rocks of the Emeishan large igneous province can be clearly divided into early (reverse polarity subzone), middle (normal polarity subzone), and late (reverse polarity subzone) stages, with a total duration of less than 1.7 m.y. (260.8−259.1 Ma). However, by combining this chronology with previously reported conodont biostratigraphic results from locations around the Emeishan large igneous province, and comparing the dominant normal-reverse polarity sequence in the Emeishan large igneous province with the geomagnetic polarity time scale, we obtain a much shorter duration of the main eruptive stage of <0.8 m.y. (260.4−259.6 Ma). About three quarters of the basalts of the Emeishan large igneous province record have a normal polarity and erupted within 0.4 m.y., while the other quarter, mainly distributed in the central zone, shows a reverse polarity and much shorter duration. Given the short duration of the eruption, gas volatiles would have been released into the atmosphere at high rates, which might provide a causal link between the rapid eruption and the end-Guadalupian mass extinction. Before the mantle plume eruption, localized eruptions probably occurred. After eruption of the mafic Emeishan flood basalts, an acid volcanic eruption occurred in the early Wuchiapingian, which was sporadically distributed in the Emeishan large igneous province.

scholarly journals Low titanium magmatism in northwest region of Paraná continental flood basalts (Brazil): volcanological aspects

2014 ◽  
Vol 6 (2) ◽  
pp. 2215-2259 ◽  
Author(s):  
F. B. Machado ◽  
E. R. Viana Rocha-Júnior ◽  
A. J. Ranalli Nardy ◽  
L. Soares Marques
Keyword(s):  
Basaltic Magma ◽  
Large Igneous Province ◽  
Flood Basalts ◽  
Continental Flood Basalts ◽  
Geological Unit ◽  
Igneous Province ◽  
Different Types ◽  
Compound Type ◽  
Incompatible Trace Elements ◽  
Northwest Region

Abstract. The early Cretaceous Paraná Continental Flood Basalts (PCFB) is considered as one of the largest volcanic provinces in the world. In Brazil, it completes the last sequence of the sedimentary Paraná Basin (Serra Geral Fm.). The geological unit is contemporary to desert sandstones of Botucatu Fm. and precedes the continental sediments of the Bauru Basin. This Large Igneous Province (LIP) is divided into different types of geochemical magmas which basically are based on TiO2 content (higher – HTi or lower LTi than 2 wt.% in TiO2) and incompatible trace elements ratio. Therefore, we studied the magma LTi (TiO2 < 2.0 wt.%), denominated Ribeira which occurs in the northwestern portion of PCFP which is poorly researched mainly in volcanological and geochemical aspects. This basaltic magma, a short expression in PCFB, occurs in the form of multiple pahoehoe flows with thicknesses ranging from 1.5 to 30 m in compound type flows under low surface slope. Peperites zones are common when associated with the first flows, and sand-filled cracks in the lower and upper edges at all pahoehoe levels when in contact with the sediment. Upward these first sequences of interactions with sediment, on the inside direction basin, simple pahoehoe flows occur being associated with Pitanga magma type (HTi, with TiO2 > 2.0 wt.%). Based on rheology data considering anhydrous environment and the composition of plagioclase (An(42–67)) and clinopyroxene (Wo(30–40)En(34–46)Fs(17–32)) showed that the LTi magma is hotter than HTi, with temperatures that range from 1069 °C to 1248 °C while for the second range from 1020 °C to 1201 °C.

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.

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