CREATE III: 東亞地函動力及板塊互動研究─藏東與鄰近地區斷層帶剪切作用研究(1/3)
Date Issued
2004
Date
2004
Author(s)
DOI
922116M002006
Abstract
The Song Ma belt, a suture zone located in between the South China and Indochina
blocks, was offset by the Dien Bien Phu Fault (DBF) in northern Vietnam. Previous studies
2
suggested that the Dien Bien Phu Fault is one of the Tertiary shear zones, resulted from the
Cenozoic extrusion tectonics due to the India-Eurasia collision. However, the timing of the
movement along DBF is remained unknown due to lacking of age constraints. In order to
reveal the movement age of DBF, schist samples from DBF and granites from the granite belt
along the northern margin of the Indochina block, were dated by 40Ar-39Ar method in the
present study.
K-feldspar, hornblende, and biotite samples form granite plutons yield very different
age ranges between the opposite sides of DBF. Hornblende separates from an undeformed
granite, on the west side, exhibit plateau dates at around 277Ma. This age appears to be
older than the early Triassic collision age (~245Ma) registered in the Song Ma suture zone
(Lepvrier et al., 1997), indicating that arc magmatism may have actively occurred on the
northern margin of the Indochina block, before the early Triassic collision. On the other
hand, deformed granitic samples from the east side of DBF exhibit plateau ages of 218-230
Ma which are younger than the collision age, which are close to the age range previously
reported for the Truong Son belt (a shear belt formed during or after the early Triassic
Indochina-South China collision event). Surprisingly, biotites and muscovites extracted
from the schists collected from DBF, also show similar 40Ar/39Ar ages ranging form 192Ma
to 211Ma, which are close to the deformation age of the Truong Son belt. This indicates
that the Dien Bien Phu Fault and the Truong Son Fault may have formed a conjugate fault
system, activated by the early Triassic collision event during the Indosinian Orogeny.
Whether the Dien Bien Phu Fault has once been reactivated by the Tertiary India-Eurasia
collision, or not? This question is still waiting for answer.
Subjects
40Ar/39Ar
Dien Bien Phu Fault
Vietnam
Publisher
臺北市：國立臺灣大學地質科學系暨研究所
Type
report
File(s)![Thumbnail Image]()
Loading...
Name
922116M002006.pdf
Size
90.03 KB
Format
Adobe PDF
Checksum
(MD5):c73b82cffa0339ca17eb0e57b7a22f9a