The purpose of this thesis is to describe the
preliminary results from the investigation of
shallow (<20m) hydrothermal vents with a total
venting area of about 0.5 km2 off the eastern tip
of Kueishantao Island. The chemical compositions
of hot fluids, sediments and rocks as well as a
continuous record of fluid temperature of a
fumarole were measured in order to understand the
venting process of hydrothermal fluids. The
continuous temperature records show that the
attainment of the maximum temperature of the hot
fluids is related to the tidal cycle. The
temperature variation seems to be associated with
changes in the boiling point of seawater, which
is affected by changes in water pressure. Such a
correlation has not been reported in the
literature. The hydrothermal fluids reach their
highest temperature about 3.5 hours after each
high tide, which is indicative of a shallow
infiltration of seawater since the time it takes
the boiling seawater to exit is so short. The
hottest temperature recorded in our study area is
116¢J, while the lowest pH is 1.75, both a record
in the world amid shallow hydrothermal systems.
And, 1.75 is the lowest pH been reported on
hydrothermal systems in the literature. At one
point, the temperature recorder was covered with
sand as a result of an encroaching typhoon. This
suggests that the topography of the study area is
susceptible to external forces.
Based on salinity, the source of the hot
fluids is taken to be ambient seawater, with no
meteoric water from the islet involved.
Concentrations of major ions in the hydrothermal
fluids are almost the same as those in the
ambient seawater. Mg is slightly enriched,
however, which is unlike other hydrothermal
fluids where, as reported elsewhere, Mg is
generally lower because it replaces Ca in the
bedrock. Low concentrations of Si in the studied
fluids make for another distinct feature.
Compared with other hydrothermal fluids in the
world, the concentrations of Si in our study area
are much lower, possibly on account of there
being insufficient time for the rock to dissolve
in the infiltrated seawater.
Black and white smokers have widely been
reported in the literature, but here are found
heretofore unheard of yellow smokers as high as 6
meters. Other than one vent which emits liquid
sulfur and forms a sulfur chimney, some vent
sulfur from sulfur mounds. Still others are low-
temperature vents which do not emit sulfur
whatsoever. The most active venting activities
are off the eastern tip of the islet. There are
no other large reliefs associated with the
hydrothermal activity, except for the chimney and
a depression down to 35m deep.
the chimney and a depression down to 35m deep.
The composition of gravel on the seafloor is
andesite, which is the same as the rock on the
islet. The major composition of the sediments
collected from the seafloor is sulfur, which is
different from the sediments of the hydrothermal
systems in the Okinawa Trough. The sulfur
particles observed in this study originate from
the fumaroles. Besides, sulfur balls the size of
softballs and with distinct growth rings are
found near some vents. The formation mechanism
of these rings at this time, however, remains
unclear. The bubbles from the vents are mostly
made up of CO2, which is different from the
composition of the shallow hot springs on the
beach of Green islet. The 3He/4He of the emitted
gas is high, this indicates that the gas may have
originated from the mantle.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0913101-095709 |
| Date | 13 September 2001 |
| Creators | Kuo, Fu-Wen |
| Contributors | Hsueh-Wen Yeh, Jung-Fu Hwang, Chen-Tung Chen, Chao-Shing Lee, Tsan-Yao Yang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0913101-095709 |
| Rights | unrestricted, Copyright information available at source archive |
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