Origin and Evolution of the Late Middle Pleistocene Trachytes in the Changbaishan Tianchi Volcano (China/North Korea): Insights from Mineralogy, Geochronology and Geochemistry
Journal
ACTA GEOLOGICA SINICA
ISSN
1000-9515
1755-6724
Date Issued
2025-05-19
Author(s)
Xiqing YE
Xu, Zhitao
Sun, Liying
Li, Zhongwei
DOI
10.1111/1755-6724.15301
Abstract
Cenozoic trachytes are characteristic of some active volcanic fields in China. In particular, the origin and
mechanisms of the evolution of trachytes from the Tianchi (Changbaishan) volcano (TV, China/North Korea) are poorly
known. Here, we present new geochronological, geochemical and isotopic data on two trachytic suites outcropping on the
northern and southern upper slopes of TV. Detailed zircon laser ablation-multicollector-inductively coupled plasma-mass
spectrometry (LA-MC-ICP-MS) U-Pb dating, Rb-Sr isochron dating of plagioclase and hornblende, 40Ar/39Ar chronology
with mineral chemistry, whole-rock element and Sr-Nd-Pb isotope data are used to explore their origins and evolutionary
mechanisms during the late Middle Pleistocene. Our data indicate that the trachytes mainly consist of sanidine, orthoclase
and plagioclase, with minor albite, quartz and hornblende. They formed at 0.353–0.346 Ma (lava flow from the northern
slope) and 0.383–0.311 Ma (lava flow from the southern slope), respectively. The TV trachytes are characterized by high
K2O/Na2O and AR values, with low A/CNK and Mg# values. They are enriched in rare earth elements (REEs; except Eu),
depleted in Sr and Ba, crystallizing at 742–858°C. The TV trachytes have high (87Sr/86Sr)i values (0.70776–0.71195),
positive εNd(t) values (0.61–2.93) and radiogenic 206Pb/204Pb values (17.515–17.806). These values are similar to those of
the Pleistocene and Holocene TV trachytes. Geochemical data indicate that they were formed by fractional crystallization
from a basaltic melt and assimilated upper crust material. The trace element pattern of the studied trachytes is consistent
with an evolution from basaltic melts representative of an enriched mantle source. The vent from which the trachytic
magma was erupted probably collapsed inside the caldera during the TV ‘Millennium’ eruption (ME) in 946 AD. The
contemporaneous emission of basaltic and trachytic magma during the Middle–Late Pleistocene suggests the coexistence of
fissural basaltic volcanism and central-type trachytic volcanism, the latter of which was associated with a magma chamber
in the upper crust during the TV cone-construction stage
mechanisms of the evolution of trachytes from the Tianchi (Changbaishan) volcano (TV, China/North Korea) are poorly
known. Here, we present new geochronological, geochemical and isotopic data on two trachytic suites outcropping on the
northern and southern upper slopes of TV. Detailed zircon laser ablation-multicollector-inductively coupled plasma-mass
spectrometry (LA-MC-ICP-MS) U-Pb dating, Rb-Sr isochron dating of plagioclase and hornblende, 40Ar/39Ar chronology
with mineral chemistry, whole-rock element and Sr-Nd-Pb isotope data are used to explore their origins and evolutionary
mechanisms during the late Middle Pleistocene. Our data indicate that the trachytes mainly consist of sanidine, orthoclase
and plagioclase, with minor albite, quartz and hornblende. They formed at 0.353–0.346 Ma (lava flow from the northern
slope) and 0.383–0.311 Ma (lava flow from the southern slope), respectively. The TV trachytes are characterized by high
K2O/Na2O and AR values, with low A/CNK and Mg# values. They are enriched in rare earth elements (REEs; except Eu),
depleted in Sr and Ba, crystallizing at 742–858°C. The TV trachytes have high (87Sr/86Sr)i values (0.70776–0.71195),
positive εNd(t) values (0.61–2.93) and radiogenic 206Pb/204Pb values (17.515–17.806). These values are similar to those of
the Pleistocene and Holocene TV trachytes. Geochemical data indicate that they were formed by fractional crystallization
from a basaltic melt and assimilated upper crust material. The trace element pattern of the studied trachytes is consistent
with an evolution from basaltic melts representative of an enriched mantle source. The vent from which the trachytic
magma was erupted probably collapsed inside the caldera during the TV ‘Millennium’ eruption (ME) in 946 AD. The
contemporaneous emission of basaltic and trachytic magma during the Middle–Late Pleistocene suggests the coexistence of
fissural basaltic volcanism and central-type trachytic volcanism, the latter of which was associated with a magma chamber
in the upper crust during the TV cone-construction stage