Data Management Center

Institute of Earth Sciences, Academia Sinica

Geomorphological mapping, 40Ar/39Ar geochronology, and geochemistry of the Huangzuei complex (Tatun Volcanic Group, Taiwan): Implications for volcanic architecture and magma generation

Alex Wei-Che Li1,2*, Kerry Sieh1,2, Kwan-Nang Pang2, Brian Jicha3, Yu Wang1, Yoshiyuki Iizuka2
1. Department of Geosciences, Naional Taiwan University, Taipei, Taiwan
2. Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan
3. Department of Geoscience, University of Wisconsin-Madison, Madison, Wisconsin, USA
citation:
Li et al.(2026) to be submitted
DOI:

Abstract

The Huangzuei complex is a volcanic complex within the 25 km-wide Tatun Volcanic Group (TVG), which is situated on the northern tip of Taiwan and poses significant potential hazards to the Taipei metropolitan area. The Huangzuei complex comprises three groups of lava flows with well-preserved landforms, radiating northwestward (HZW), northeastward (HZE) and southeastward (HZS) up to several kilometers from cratered summit of the complex. High-resolution topography from a LiDAR-based bare-earth DEM enables detailed demarcation, characterization, and volume calculation of individual flows of the Huangzuei complex. Detailed geomorphological mapping and thirteen newly obtained 40Ar/39Ar ages reveal that the Huangzuei complex undergoes four eruptive stages, with the earliest one beginning at ~140 ka, followed by the most vigorous one from ~129 ka to ~133 ka. Eruption resumed at ~117 ka after an ~10 kyr quiescence. A volcaniclastic deposit atop the HZS1 flow, which might result from edifice collapse, contains blocks that are ~85 ka. It is thus likely that the Huangzuei volcanism ended in the formation of domes and a summit crater at 85 ka or later. Samples from the Huangzuei complex are mostly olivine-bearing andesite with arc-like geochemical features. Wide compositional ranges of phenocrysts, including plagioclase (An52-95), clinopyroxene (Mg#72-91), orthopyroxene (Mg#62-77), and olivine (Fo74-88), imply a complicated magma assembly in the formation of the Huangzuei complex. Disequilibrium textures, including oscillatory zoning, reverse zoning, partial resorption, and development of reaction rims, are common in the major phenocrysts, including plagioclase, pyroxenes and olivine. These wide ranges of differentiation indices, together with abundant disequilibrium textures, indicate that the transcrustal magmatic system beneath the Huangzuei complex might comprise three predominant magmatic reservoirs with distinct evolved extents. Intense magma hybridization prior to eruptions, involving periodic replenishment by more primitive magmas and mush disruption and disaggregation, is the main mechanism to trigger an eruption. Based on the detailed geomorphological map, robust 40Ar/39Ar ages and exhaustive mineral chemistry data, this study establishes comprehensive evolution of the Huangzuei complex and highlights potential hazards that might occur around a young volcanic complex in the TVG.

Downloads

Table C.1a. Olivine compositions obtained from cores of selected grains (in wt.% oxides)
Table C.1b. Olivine compositions obtained from traverses of selected grains (in wt.% oxides)
Table C.2a. Orthopyroxene compositions obtained from cores of selected grains (in wt.% oxides)
Table C.2b. Orthopyroxene compositions obtained from traverses of selected grains (in wt.% oxides)
Table C.3a. Clinopyroxene compositions obtained from cores of selected grains (in wt.% oxides)
Table C.3b. Clinopyroxene compositions obtained from traverses of selected grains (in wt.% oxides)
Table C.4a. Plagioclase compositions obtained from cores and rims of selected grains (in wt.% oxides)
Table C.4b. Plagioclase compositions obtained from traverses of selected grains (in wt.% oxides)
Table C.5a. Amphibole compositions obtained from cores of selected grains (in wt.% oxides)
Table C.6. Chromite compositions obtained from cores of selected grains (in wt.% oxides)