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Fig. 4.35 a, b, c Geological setting and, b digital elevation model (DEM) for Ulleung Island
(950 m above sea level). Stars in (a) represent sites of Quarternary intraplate volcanic activity and
cross-hatching indicates volcanic arcs. UB, YB and JB are the Ulleung, Yamato and Japan Basins.
The JB is the only part of the East Sea/Sea of Japan to have experienced new oceanic crust
formation, the rest being variously stretched continental bloks (Tamaki et al. 1992). The numbers
in (b) indicates locations of UL series whole-rock samples. The tephra samples and associated
accidental lithics were collected within the dotted region inside the Nari caiidera. c Schematic
stratigraphic column (not to scale) and nomenclature with sample groupings; simplified after Kim
et al. (1999), Brenna et al. (2014)
Fig.
4.35
a and b, whereas stratigraphic succession of various tephras and trachytic
dykes and basalts are Fig.
4.35
c. The youngest eruptions, post 20 ka BP, were
explosive, generating thick tephra sequences of phonolitic composition (Stage 4),
which also entrained phaneritic, porphyritic and accidental cumulate-bearing rock
types. Major element chemistry of the evolved products show a continuous spec-
trum of trachyte to phonolite compositions, but these have discordant trace element
trends and distinct isotopic characteristics, excluding a direct genetic relationship
between the two end-members. Despite this, the Stage 3 trachytes and some por-
phyritic accidental lithics have chemical characteristics transitional between Stage 2
trachytes and Stage 4 phonolites. Within the phonolitic Stage 4 tephras three
subgroups can be distinguished. The oldest, Tephra 5, is considerably enriched in
incompatible elements and chondrite-normalized rare earth element (REE) patterns,
which display negative Eu anomalies. The later tephras, have compositions inter-
mediate between the early units and the trachyte samples, and their REE pattern do
not have signi
cant Eu anomalies. The last erupted, Tephra 1, from a small intra-
caldera structure, has a distinct tephriphonolite composition. Trace element and
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