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| Titel |
Geochemical Characteristics of Metavolcanics in the Area from Slate Formations of Southern Central Range, Taiwan |
| VerfasserIn |
W.-S. Lyu, W. Lo, S.-R. Song |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250064497
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| Zusammenfassung |
| The Central Range of Taiwan located at the convergent boundary of the Eurasia Plate and the
Philippine Sea Plate accounts for 60% of total area of Taiwan. The rock types of
Central Range include slates, phyllites, schists, gneisses, amphibolites, marbles, and
some metaigneous rocks. In recent years, much attention has been given to the
tectonic history in the Central Range of Taiwan. This notwithstanding, before the
arc-continent collision began tectonic evolution that either passive continental margin of the
South China Sea or active continental margin of the East China Sea has been a
subject of much debate. Therefore, the petrogenesis of the metavolcanic rocks has
the inseparable relation with the tectonic evolution of the Taiwan. According to
previous studies, these metavolcanic rocks are exposed at widely scattered places in
the Central Range of Taiwan. The purpose of this study is to present petrological,
geochemical data (major and trace elements) and Sr-Nd isotopic analyses of the
metavolcanic rocks of Shinkangshan area and the nearby associated Hsiangyangshan
area.
According to the chemical compositions, the metavolcanic rocks from the Shinkangshan
area have SiO2 contents in the range of 48.29-51.35 wt.%. On the other hand, the
metavolcanic rocks from the Hsiangyangshan area are characterized by SiO2 contents from
49.79 to 65.93 wt.%. On the Chondrite-normalized REE patterns, the Shinkangshan
metavolcanic rocks show (La/Sm)N =1.88-2.87 and (La/Yb)N =3.41-5.89 and minor positive
to non-existent Eu anomalies (Eu/Eu*=0.89-1.00), similar to the oceanic island
basalts. The Hsiangyangshan metavolcanic rocks show fractionated REE patterns
with (La/Sm)N=1.23-2.07, (La/Yb)N=1.42-2.68 slightly negative Eu anomalies
(Eu/Eu*=0.59-1.18).
Primitive mantle-normalized abundance patterns and Sr-Nd isotopic compositions show
that the Shinkangshan metavolcanic rocks have geochemical patterns characterized by
enrichment in HFSE and LREE relative to HREE, as well as depletion in LILE. Sr–Nd
isotopic compositions of samples from the Shinkangshan metavolcanic rocks were analyzed
and fall in a range of 0.70364 to 0.70372 for 87Sr/86Sr and of +5.93 to +8.0 for ÉNd. These
data indicate that the metavolcanic rocks of the Shinkangshan area are tholeiitic basalts
in composition and exhibit a range of intra-plate environments. By contrast, the
Hsiangyangshan metavolcanic rocks are volcanic arc basalts and chemical composition
exhibit the depletion of Nb, Ta and Ti with remarkable enrichment in Th concentrations, the
enriched Sr-isotopic (87Sr/86Sr ratios from 0.70510 to 0.70571) and slightly depleted
Nd-isotopic (ÉNd values from +2.95 to +3.08). These geochemical characteristics and
isotopic compositions suggest significant contributions of subduction zone-related source
rocks. |
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