scholarly journals Magma Plumbing System of Emeishan Large Igneous Province at the End-Permian: Insights from Clinopyroxene Compositional Zoning and Thermobarometry

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 979
Author(s):  
Jun-Hao Hu ◽  
Jing-Wen Liu ◽  
Tao Song ◽  
Bai-Shun Shi
Keyword(s):  
Tectonic Setting ◽  
Large Igneous Province ◽  
Magma Ascent ◽  
Magma Chambers ◽  
Flood Basalts ◽  
Compositional Zoning ◽  
Magma Plumbing System ◽  
Emeishan Large Igneous Province ◽  
Mafic Intrusions ◽  
Igneous Province

The end-Permian Emeishan Large Igneous Province (ELIP) in SW China is widely accepted to have formed by mantle plume activities, forming voluminous flood basalts and rare picrites. Although many studies were performed on the petrogenesis and tectonic setting, the detailed conditions and processes within the magma chamber(s) remain unsolved. In this study, we studied the sector-/oscillatory-zoned clinopyroxene (Cpx) phenocrysts and performed Cpx-liquid thermobarometric calculation to constrain the physicochemical processes within the magma chambers. The results show that Cpx phenocrysts from the high-Mg basalts were crystallized at 4–27 (average 17) km, whilst those from the low-Mg basalt were crystallized at 0–23 (average 9) km depth. The sector and oscillatory Cpx zoning in the high-Mg basalts show that the magma had experienced undercooling and multistage recharge events in the deep-staging chamber(s). The magma replenishments may have eventually led to the eruption of high-Mg basalts, and magma ascent to the upper crust for further fractionation to form the low-Mg basalts and mafic intrusions.

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 A lower crust origin of some flood basalts of the Emeishan large igneous province, SW China

2015 ◽  
Vol 109 ◽  
pp. 74-85 ◽  
Author(s):  
J. Gregory Shellnutt ◽  
Tadashi Usuki ◽  
Allen K. Kennedy ◽  
Han-Yi Chiu
Keyword(s):  
Lower Crust ◽  
Large Igneous Province ◽  
Flood Basalts ◽  
Sw China ◽  
Emeishan Large Igneous Province ◽  
Igneous Province

Origin of K-feldspar megacrysts in rhyolites from the Emeishan large igneous province, southwest China

Lithos ◽  
2017 ◽  
Vol 294-295 ◽  
pp. 397-411 ◽  
Author(s):  
Li-Lu Cheng ◽  
Yu Wang ◽  
Jason S. Herrin ◽  
Zhong-Yuan Ren ◽  
Zong-Feng Yang
Keyword(s):  
Southwest China ◽  
Large Igneous Province ◽  
Emeishan Large Igneous Province ◽  
Igneous Province
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