Detrital zircon U-Pb dating of the Tananao Schist in the Nanao region, eastern Taiwan
Date Issued
2016
Date
2016
Author(s)
Lin, Hong-Chih
Abstract
The Tananao Schist exposed from Dongao to Nanao region is located in the northern part of the eastern limb of Central Range. The lithological characters include quartz-mica schist, metachert, black schist, thin layer of marble, green schist, amphibolite, and gneiss. The Tananao Schist experienced the Nanao Orogeny and Penglai Orogenies. It is difficult to identify the relationships between various schists due to the above-mentioned two orogenies buy reginal metamorphism. In addition, previous studies provided insufficient information of fossil records and dating in the Tananao schist; therefore, it is very difficult to diseriminal the stratigraphic sequerence of these schists. Accordingly, zircon U-Pb dating was used to analyze the quartz-mic schist, green schist, metachert, and gnesiss in this study and determine the stratigraphic age. This study can help us to unravel the tectonic environment of the Tananao schist in Dongao and Nanao region. We analyzed 24 samples and obtain the results of the detrital zircons U-Pb youngest age. In assumption, we could discover the youngest age of detrital zircon of the sedimentary rock in oringal, as if we could find simultaneously igneous rocks that eroded and replaced in the same age. The schists from Dongao Schist, Nanaoling Schist, and Wuta Schist all have some common features such as the sedimentary rocks from the late Cretaceous as well as some other aged. The youngest depositional age is 75±2 Ma among various layer ages. The age may be presented a tectonic mélange in origen. During the late Mesozoic, the Paleo-Pacific Plate subducted beneth to the Cathaysia Bolck. The Paleo-Pacific oceanic plate has been squeezed and ruptured, withing the subduction zone, all different layers from different ages then have been mixed together such as amphibolite, marble, metamorphic rock, meta-volcaniclastic rock, quartz-mica schist, and green schist. Hence, it is suggested that the schists was situated in a tectonic mélange until 75 Ma at least.
Subjects
detrital zircon
U-Pb dating
the Tananan Schist
Creataceous
melange
Type
thesis