In this Space shuttle photograph, southwest is
towards the top. The picture shows the Tsaidam Basin (bottom
right), Kunlun Mountains (snow-capped peaks diagonally across
center) and part of the Tibetan Plateau (southern upper half).
The Kunlun Mountains consist of Permian batholithic rocks and
Paleozoic metasediments into which they were intruded. On the
north, the mountains are bounded by a thrust fault buried beneath
the alluvial fans and young sediments of the Tsaidam Basin.
Golmud is located at the mouth of the major valley cutting across
the Kunlun range.
Two major left-lateral strike-slip faults are revealed in this
picture. The prominent Xidatan-Tuosuohu-Maqu Fault runs along the
south edge of the western part of the range (upper right) and
branches cuts in the left-center of the photograph. The XTM fault
continues straight, whereas the Kunlun Pass Fault curves along
the southern margin and heads southeast (straight towards the
edge of the photograph). The XTM Fault has reoccupied the
Kunlun-Qinling Suture.
Our route steps through the mountains, taking advantance
of the major E-W valleys by following the Golmud River as it cuts
across the ranges. The road emerges on the Plateau near where the
XTM fault branches. Uplift of the mountains has produced valleys
with multiple stranded terraces, as the Golmud River cuts rapidly
downward (right). NASA's on-line geomorphology book describes the
strike-slip faults of western China, including the Kunlun
Fault.
We stop at Naij Tal, which is at about 4000 m (c.
13,000') elevation, to view the Kunlun Mountains. We are in the
Xidatan-Dongdatan valley, which follows the XTM Fault. Professor
Lin tells us that the fault displays some thrust movement, but is
dominantly strike-slip. Its trace is indicated by triangular
facets and scarps at the base of the mountains.
Spectacular glaciers descend from the Kunlun
Mountains. One particularly fine example descends from
snow-capped Yuzhu Peak that is 6177 m (20,260') high. Lateral
moraines embrace its long tongue of ice.
The final stretch of road up to Kunlun Pass follows a steep
stream. Along it, gold miners are working the placer deposits.
Their equipment consists of a few water pumps and hoses, many
shovels and some sluice boxes. Judging from the places that they
are concentrating their efforts, the gold is concentrated at the
base of the alluvial fans along the stream.
Kunlun Pass at 4772 m (15,656') is marked by a plaque
flanked by two brightly painted statues of a snowlion and an
eagle. Colorful prayer flags hang in long strings from a pole
behind the marble monument. The strike-slip Kunlun Pass Fault,
which runs beneath the Neogene cover near the pass, marks the
boundary between the Kunlun Terrane and the Songban-Ganzi
Terrane. Ophiolitic material has been faulted out in this area,
but it does occur to the east along the extension of the fault.
The ocean between the Kunlun and Songban-Ganzi terranes closed in
the Permian. Rocks of the Kunlun block include Ordovician,
Devonian and Carboniferous sediments; the granites are probably
Permo-Triassic. The Songban-Ganzi rocks are predominantly
Triassic sediments.
