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Introduction
The pre-Tertiary metamorphic complex is exposed mainly in the eastern part of the Central Range and
constitutes the eastern subprovince of the Central Range geologic province. It forms the oldest geologic
element of Taiwan. The metamorphic belt is exposed over a north-south length of 250 kilometers and maximum
width of 30 kilometers in the north. The width, of the belt diminishes to 20 kilometers in the middle part
and to 10 kilometers in the south at Taitung. This belt covers approximately 4,600 square kilometers and
underlies about 14 percent of the land area of Taiwan. The metamorphic rocks in the complex are represented
by an assemblage of metasedimentary and metavolcanic rocks composed largely of schists and metamorphosed
limestone. Subordinate amounts of gneisses, migmatite, amphibolite, serpentinite, and mafic to ultramafic
igneous rocks are also found in the metamorphic rocks. Various kinds of dikes and quartz veins are scattered
in the schistose, gneissic and other rocks. All these rocks are grouped on the legend under the general
stratigraphic term "Tananao Schist." Three varieties, black or pelitic schist, greenschist, and siliceous
schist, are by far the dominant rock types in this belt (Yen, 1954a). The metamorphic terrain is heavily
forested, and marked by precipitous mountains and rugged topography. The whole area is scarcely populated
and accessibility is difficult. Detailed geologic mapping is extremely laborious if not impossible.
Most parts of this metamorphic province have been studied only in reconnaissance, with very little
systematic detailed mapping. Critical geologic information is still lacking for much of this province,
except locally accessible areas that are close to the coast, or to main highways, or to the Longitudinal
Valley. In areas where mining or logging are taking place, more detailed geologic study has been undertaken
to evaluate mining and development potentials. These areas include the Suao-Nanao area in northeastern
Taiwan, the Tailuko drainage near Hualien, the Fengtien-Wangyung-Juisui area south of Hualien, and Yuli in
Hualien-hsien. In addition, the metamorphic rocks exposed along the three main cross-island highways have
been studied in considerable detail for engineering and economic purposes. However, all these well-studied
areas make up only a small portion of the immense metamorphic belt. More efforts to conduct extensive
studies in other remote areas are required before we will be able to delineate the complex geologic and
tectonic history of the entire metamorphic complex.
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:::© CENTRAL GEOLOGICAL SURVEY, MOEA
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