GSW: 2000
MEETING MINUTES
Geological Society of
Minutes of the
1323rd Meeting, Wednesday, January 12, 2000,
Powell
Auditorium, Cosmos Club.
President Hammarstrom called the meeting to
order at 8:01 PM. The minutes of the
1322nd meeting were accepted as read.
Visitors
consisted of Ward Sanford and Kurt Hinaman of the USGS Water Resources
Division; Stan Mroczowski, USGS geochemist,
A guest book was started to record the names
of visitors.
There were no new members.
Cy Galvin invited members to a meeting of the
Potomac Geophysical Society on January 20, at which he will give a presentation
on “The Extreme Coastal Storm Affecting New York in December, 1992: Physical
Damage, Social Response, and a Seismic Event.”
President Hammarstrom introduced the new
committees for the upcoming year. There
were no informal communications.
Spatial Patterns Of Diagenesis
During Geothermal Circulation In Carbonate Platforms, Alicia Wilson,
Dolomitization can affect the hydraulic
properties of carbonate rocks and may play an important role in the geochemical
evolution of basin pore fluids, but the origin of massive dolomite is not well
understood. Laboratory and field
observations indicate that dolomitization is limited severely by kinetic
processes at low temperatures, and researchers have suggested that geothermal
convection of seawater deep in carbonate platforms could provide the necessary
supply of magnesium for dolomitization at temperatures high enough to overcome
kinetic limitations. Quantitative
reactive-transport simulations were presented that allow prediction of the
rates and spatial patterns of dolomitization during geothermal convection. Complete dolomitization in warm areas of a
platform is predicted over 10 to 50 My, depending on the flow system. Simulations suggest that dolomitization
during geothermal convection could create calcium-rich fluids, and results are
consistent with field observations of calcium-rich warm springs on the west
coast of
Questions by Cy Galvin, Steve Shirey, Jane
Hammarstrom,. Chris Neuzil, Nathalie Marchildon, and two unidentified.
Electron Microprobe Dating Of Monazite, John
M. Hanchar, Dept. of Geology, The
There have been many advances over the past ten
years using the electron microprobe to date geologic events using the mineral
monazite [(Ce,La,Nd,Th)PO4]. Determining and improving the
analytical precision of monazite analyses can be achieved by using long
counting times per analysis, increasing the number of analyses, or both.
Determining the accuracy of such measurements, however, is more problematic due
to the fact that small inaccuracies in the Pb content measured with the
electron microprobe can lead to large variations in the calculated age. In the
speaker’s experience, the calculated ages are usually significantly older than
ages determined using isotopic dating techniques on the same monazite
grains. He and co-workers have dated
several monazite grains that are used as standards for the Sensitive
High-Resolution Ion Microprobe II (SHRIMP II) geochronology laboratory at the
Geological Survey of Canada with the electron microprobe, and monazite grains
from a placer deposit from western
Questions by Steve Shirey, Jane Hammarstrom,
Mike Braun,
The 1999 Mid-Atlantic Drought: Lessons Learned And Looking Ahead,
Robert Hirsch,
Droughts represent an interface between
science and public policy. A drought is
defined by its societal effects, not strictly in scientific terms. It is not simply a climatic phenomenon. The effect of a drought depends on the effect
considered, its duration, and the area affected. There are various types of drought: climatic
droughts, agricultural droughts, ecological droughts, hydrologic droughts,
water supply droughts, and political droughts.
The 1999 Mid-Atlantic drought was illustrated by the discharge of the
Questions by E-an Zen (2), Jane Hammarstrom,
Dallas Peck, Steve Shirey (2), Mark Anderson, and one unidentified.
Attendance was 65. President Hammarstrom adjourned the meeting
at 9:39 PM.
Respectfully submitted,
Mark McBride,
Meeting Secretary
Geological Society of
Minutes of the 1325th (and 1324th) Meetings, Wednesday, February 9, 2000, Powell Auditorium,
Cosmos Club.
President
Hammarstrom called the meeting to order at 8:00 PM.
The
1324th meeting was originally scheduled for January 26, but the
meeting on that date was cancelled because of a severe snowstorm. A pre-meeting poll of various older and wiser
members reached the consensus that today’s
meeting was the 1324th meeting, only delayed. However, by presidential fiat, it was
declared to be the 1325th meeting.
Therefore, there was no 1324th
meeting.
The
minutes of the previous, or 1323rd, meeting were accepted as read.
Visitors
consisted of Terry Green, of the
New
members were announced, after having been approved at the board meeting this
afternoon. They were:
Chip Groat – USGS
Amitava Gangopadhyay
–
Kevin Marvel – American Astronomical Society
Tim Cohn – USGS
Four
announcements were made:
The deaths of Howard Evans and Lou Walter
were announced, and a moment of silence was observed.
Brett Leslie announced the Annual Meeting of
the Geological Engineering Society. Dan
Goldin, the administrator of NASA, has been invited to speak.
Mark Zerniak asked members to inspect copies
of the draft Chesapeake Bay Agreement, which are available at the back
table.
…and a happy birthday was wished to Pete Stiefel.
There were no informal communications.
The meeting was a special Video Night, making
use of the new video projection equipment in the Powell Auditorium. Two formal presentations were made, the first
using video for much of the presentation, the second consisting almost entirely
of a video:
Biogeochemical Influences on Methane Hydrate Formation and
Stability, Richard Coffin, Naval Research Laboratory.
Over
the past fifteen years, methane hydrates have become recognized as an abundant
energy reserve in the world coastal margin.
Methane hydrates form when methane becomes trapped within an ice
crystalline structure under high pressure and low temperature. In appearance, they are waxy white or yellow
solids. One m3 of gas hydrate
can contain 164 m3 of methane.
They are very common in coastal areas.
The
presence of the hydrates has initiated investigations of alternate energy,
coastal stability, ocean carbon cycling, and global economy. The Naval Research
Laboratory (NRL) has initiated a 5-year research program designed to study
methane hydrates in the coastal ocean floor.
The Navy is interested in methane hydrates because of how their release
affects the acoustical properties of sediments, and because of their effects on
the geotechnical properties of sediments, which may endanger the stability of
structures in or on the ocean floor.
Research at NRL integrates the Navy priorities with these international
scientific and economic topics.
This work
was initiated, at NRL, with research cruises in the Gulf of Mexico and the
A
video, taken on submarine dives in the Gulf of Mexico, showed three diverse
sites; 1) a region with a large abundance of tube worms, 2) a brine pool that
supports an active chemosynthetic mussel community, and 3) a sediment surface
methane hydrate, at a temperature of 6° C, that is surrounded with an active
biological community. Data presented
included preliminary carbon isotope analyses of carbon pools which suggest that
the methane hydrates reflect a significant source of old (isotopically light)
carbon from considerable depths.
Questions
were by Steve Shirey, Steve Huebner, and Pete Stifel, an eastern shore
farmer.
Geology Goes
In
the words of the presenter:
Geology Goes Hollywood arose out of a symposium at GSA Boston in
1993 examining "How the General Public Perceives Geology". Various modes of access to geology by the
general public were discussed during the session. Speakers included Sorena Sorensen on Museums,
Chet Raymo of the Boston Globe on newspapers, Don Hyndman of "Roadside Geology"
books, etc. All were in honor of John Shelton and his contributions to
visualization in geology.
My
youngest daughter, Deborah Steller, is a TV producer. We combined to present how the general public
perceives geology through the movies by using clips from some 50
Over
the subsequent years we have had many requests to duplicate the video, but
since copyright laws preclude that step, and because we are within the three
minutes limit for extracted footage and not making a profit, we simply show the
25 minute video for educational purposes when asked.
Since
in the last few years
There
was one question by Nathalie Marchildon.
Attendance was 62. President Hammarstrom adjourned the meeting
at 9:27 PM.
Respectfully Submitted,
Mark McBride, Meeting Secretary
Geological
Society of
Minutes
of the 1326th Meeting, Wednesday,
March 8, 2000
Powell
Auditorium, Cosmos Club.
President
Hammarstrom called the meeting to order at 8:01 PM. The minutes of the 1325th meeting
were accepted as read.
Visitors
consisted of Fred Block, Office of Surface Mining; Pingwa Chow, China Institute
of Mining Technology; Perle Dorr; and Bill Althoff, Air and Space Museum.
Five
announcements were made:
Gordon
Nord requested judges for a number of science fairs.
Bill
Minarik pointed out that a large bedrock excavation was taking place in
Jeff
Grossman announced that he has the last 20 years of GSW minutes on the web
site.
We
can have 6 more delegates to AAPG: Who wants to be a delegate?
Don’t
park in the Cosmos Club lot and say that you are here for GSW!
There were no informal communications.
Active
geothermal systems in the Taupo Volcanic Zone provide invaluable analogues to help
us understand the processes that form epithermal deposits. The zone lies along the boundary between the
Pacific and Australian Plates, which cuts through
The
Golden Cross mine is a classic low sulfidation epithermal ore deposit in the
Hauraki goldfield of
Detailed
underground mapping has revealed that Golden Cross contains over eight
generations of veins. Most of the gold
recovered from the underground workings was extracted from colloform banded
quartz veins, which formed relatively early.
Structural analysis indicates that barren and mineralized veins formed
in an extensional regime, and that the deposit underwent significant rotation
after the underground veins formed.
Discovery of bedding dipping near 45 degrees now indicates that
extension occurred when the present high-angle veins were close to
vertical.
Questions: Jane Hammarstrom (2), Paul Barton,
Mark Fratke, Amelia Logan.
Recent
legislation has given the US Army Corps of Engineers a role in the restoration
of abandoned mine lands. Issues include
safety – eg entry to tunnels; abandoned hazardous wastes; tailings; acid mine
drainage; and “scam” mining on public lands.
The nature of this role in presently evolving both through the
development of internal Corps policy as well as through the legislative and appropriation
processes in Congress. A consortium of
Corps district offices in the Western states has formed a group called RAMS
(Remediation of Abandoned Mine Sites) to facilitate the use of Corps resources
by other Federal and State agencies.
Major policy issues being resolved include: (1) proposals
for a number of partnered demonstration projects; (2) development of an AML
technology database; (3) developing partnerships with non-governmental
organizations; (4) sharing responsibilities and costs with other Federal
agencies, (5) reducing potential liability by focusing on ecosystem restoration
of the entire watershed; (6) remediation of safety & health hazards; (7)
streamlining the Corps planning process.
The Corps Headquarters' staff is presently preparing a position paper on
an AML program for approval by Senior Management.
Questions: Pete Toulmin,
Moto Sato.
Geochemistry of Acid Mine Drainage from the Abandoned
The
USGS, in cooperation with a local citizens group (the Elizabeth Mine Study
Group), is characterizing acid mine drainage from the abandoned Elizabeth mine
site to serve as the basis for potential future reclamation. This site is close to being listed as a National
Priorities List (Superfund) site.
pH SO4 Fe Cu Zn
mg/L mg/L mg/L mg/L
South Pit 3.7
- 4.5 92 0.043 0.011 0.005
Draining Mine Workings
5.1
- 6.0 550-560 45.7 0.040 -
Ground Water Seeps
6.1
- 6.9 50-3,600 11.0-560 0.001-0.013 0.0006-17.0
Surface Waters
2.1 - 3.2 330-1,700 32.0-200 8.8-55.0 2.5 - 17.0
The
pH of the seep waters rapidly decreases downstream due to the oxidation and
hydrolysis of iron species, such that Copperas Brook has a pH of ~2.7 prior to
emptying into the river. In the dry
season, the acidity and heavy-metal content of surface waters can be
dramatically increased through the dissolution of efflorescent salts such as
melanterite and rozenite during storm events.
Of the heavy metals, only Cu, Zn, and Cd exceed U.S.E.P.A. guidelines
for acute toxicity in freshwater aquatic ecosystems, consistent with the geochemical
characteristics of the deposit.
Studies
at the mine reflect the USGS’s general shift from classical economic geology to
mineral remediation studies.
Technically, this involves a shift of emphasis from high to low
temperature geochemistry, and from equilibrium to disequilibrium
condition. There is now a greater need
to intertact with numerous different groups with different agendas.
Questions:
Hal Gluskotter, Dan Milton, Pete Toulmin, Doug Rankin, and John Slack.
President
Hammarstrom announced that next week would be Federal Science Night.
Attendance
was 68. President Hammarstrom adjourned
the meeting at 9:46 PM.
Respectfully Submitted,
Mark McBride, Meeting Secretary
Geological
Society of
Minutes
of the 1327th Meeting, Wednesday,
March 22, 2000, Powell Auditorium, Cosmos Club
President
Hammarstrom called the meeting to order at 7:59 PM.
The
minutes of the 1326th meeting were accepted as read.
Visitors
consisted of John Brice, State Geologist of Nevada; Gretchen Onstad,
Two
announcements were made:
On
May 13, Michael Wise of the Smithsonian will lead a field trip to the Moorfield
Pegmatite in
We
still need to elect five delegates to the AAPG; interested persons please see
President Hammarstrom after the meeting.
There were no informal communications.
The meeting was significant in that all three
speakers ran significantly over the customary 20 minutes. Because of their eminence, no action was
taken.
Digital Earth: the Web-Wide-World
(26 minutes), Alan Gaines, National Science Foundation:
The “Digital Earth” is a concept for a
worldwide database that provides a browseable 3D representation of the earth.
“Digital Earth will be a virtual representation of our planet that enables a
person to explore and interact with the vast amounts of natural and cultural
information gathered about the Earth.” (Consensus definition adopted at the
Second Interagency Digital Earth Workshop [IDEW2], held 1999 September 22-23 at
University of Maryland.)
Conceptually, it is a distributed geolibrary
of “metadata” – data about sources and archives of data – implemented through
the internet and related technologies.
Its aim, to combine data for beneficial use, is broadly shared within
the geoscience community. A convergence
of science and technologies, including the internet, satellite imagery, and the
global positioning system, now makes such a system thinkable. A prototype is now available through the
World Wide Web at http://www.digitalearth.gov/.
Earth is an integrated system of parts and
interfaces. We have tended to confine
ourselves to one part, such as the lithosphere, but we need now to combine our
perspectives and look at interactions among the parts. The challenge, then, is to combine widely dispersed
data, in various forms, to generate information, and from this, knowledge.
The hardest part is integrating the
components of such a data system so they can interoperate. These components include computer systems and
software of many kinds. But besides
these narrowly technical problems, there is also the problem of finding where
all the data is, that could become part of such a system. Not enough attention has been paid to this issue.
Implementation of the Digital Earth is
starting with an interagency group led by NOAA and includes also
nongovernmental organizations such as the National Geographic Society. A series of workshops is being planned to
create guidelines for data integration, engage the earth sciences community,
and identify and address technical and cultural barriers.
Questions: Mack Ross, Rama Kotra, and Jane
Hammarstrom.
Strategic Change at the USGS: What's In It
for Science? (23 minutes), Chip Groat, U.S. Geological Survey, Reston:
The USGS’s new director sees specific needs
for the organization, in particular for the USGS to see itself as one
organization, not four; and for the organization to have a single set of
operating procedures. In this vein, he
has reorganized the Director’s office, given the Regions more responsibility,
and added headquarters responsibilities to division (or more properly,
discipline) chiefs. The USGS is trying
now to ask users what they need, and to focus its activities accordingly. The focus is on raising the profile of the
USGS with the public and the larger scientific community.
But where is the science in all this? Because of its organizational position, it is
relatively hard for the USGS to become visible; it is not too well known on
Capital Hill outside its “own” congressional committee. The USGS does not have a customer base
outside, e.g. in the universities (as is the case with the National Institutes
of Health, for example), since so much of its work is done in-house. Funding tends to be related to
attention-getting issues such as floods and earthquakes. Discipline-based studies will remain significant,
but he sees the growth areas for USGS science in the areas of complex systems
and the interfaces between systems.,
Where is the USGS going in a strategic
sense? We can ask, where are the
problems we will need to address? To
help identify these, he is giving the Associate Directors more responsibilities
in identifying research focuses.
Dimensions that need to be added to the USGS’s vision include: How do we
measure increased understanding of important elements? How do we improve predictive abilities? We need to think hard about where the USGS’s
understanding and abilities should be focused.
Strategic
change along these lines must pay off in enabling USGS personnel to do science
better, and to better apply their discoveries.
Questions:
Moto Sato, Rosalind Helz, Mack Ross, Brett Leslie, and Bruce Lipin.
The Role of science in SCIENCE in the Voxellated 21st Century (21.5 minutes), Nicholas B. Woodward,
Department of Energy:
An essential question today is what are the
roles of scientific investigations and scientific data in developing and using large
scale computational models for performance prediction and assessment in the
coming century. This is particularly
important in the context of governmental bodies using these predictive models
as the basis for policy formulations. The evolution of modeling in structural
geology over the last century is taken as one way to understand the evolution
of approaches and some of the pitfalls in the modeling business. It also
suggests an answer to the question of roles.
Although computational models are outstanding new tools, and they enable
us to do things we have never done before, they are never better than the
quality of the questions asked of them, nor can they substitute for wise
decision making using them as one, but not the only input.
Attendance was 68. President Hammarstrom adjourned the meeting
at 9:57 PM.
Respectfully Submitted,
Mark McBride, Meeting Secretary
Geological
Society of
Minutes
of the 1328th Meeting, Wednesday,
April 5, 2000
Powell
Auditorium, Cosmos Club.
President
Hammarstrom called the meeting to order at 8:00 PM.
The
minutes of the 1327th meeting were accepted as read.
Visitors
consisted of Darrell Simms, SWRI.
Four
announcements were made:
A
moment of silence was observed for two persons deceased. Hal James, a former member, was formerly the
Chief Geologist of the USGS. Dr. I.
Gregory Sohn was a member since 1947. He
spoke in 1966 and gave many informal communications.
According
to Gordon Nord, judging of three science fairs has been carried out successfully,
and one more will take place on April 8.
The
field trip to the Moorfield Pegmatite Mine,
Four
new AAPG delegates have been selected.
They are Hal Gluskoter, Cy Galvin, Bob Burruss, and Suzanne
Weedman.
There
were no informal communications.
The
Global Circulation Models (GCMs) predict that
the
The past decade has seen a significant
warming globally but more so in the
In order to improve GCM and other model
simulations and predictions of Arctic climate and the environmental response,
NSF and ONR are supporting the Surface Heat Budget of the Arctic (SHEBA) Ocean
project.
One of the unexpected results was the
discovery in October, 1997 that a major melt season the previous summer had
resulted in a normally three meter thick ice cover being reduced by 40%. The loss of the ice nearly imperiled the
selection of a site for the experiment.
While ice grew back during winter, a longer-than-normal melt season in
1998 left the ice pack thickness at only one meter at the end of the field
experiment. Considering the site had
drifted over 100 miles further north during the year, which would have been
expected to produce thicker ice near the site, could this be an important
symptom leading to the canary's cough?
Researchers also have determined that some of the "standard"
values used in GCMs varied significantly during the year so that an annual
"average" is not representative of much of the year.
Questions: Cy Galvin, Mack Ross, and E-an
Zen.
Evidence of multiple asteroid impacts from Late Archean to
Paleoproterozoic successions in
A number of spherule layers have been found
near the Archean-Protoerzoic boundary (ca. 2.5 Ga) in
The spherulite layers are on the order of 1
cm thick, and occur at exactly the same stratigraphic position over distances
of approximately 300 km. This is the
right geometry for a strewn field. An
iridium anomaly was observed with the spherules from the
The spherule layers appear to be thicker and
to represent more basaltic material than similar layers in the
Phanerozoic. These may result form
larger impactors, less extensive continental crust, or a generally shallower
world ocean.
Questions: George Helz, Jane Hammarstrom, Joe
Smoot, Bill Burton, Dan Milton, Nita Sahai.
How Algae Grow Shells of Glass: Silica
Biomineralization by Diatoms, Nita Sahai , Department of Chemistry and Biochemistry,
The study of
biomineralization brings together geochemistry and biochemistry.
Biologically formed minerals are uniquely strong, among other things, so
there is much interest in the processes by which they are formed. Diatoms are a good example. They are algae that secrete silica shells,
and, in the process, help control geochemical cycling of silica, carbon, and
phosphorus. Biological components within
the silica shells tend to be enriched in proteins and polysaccharides. Silica may be polymerized to various degrees;
NMR is a useful technique for studying this polymerization. Issues being studied include: How is silica
transported? What kinds of bonds exist
between silica and organic components?
Are proteins and polysaccharides involved in nucleation of silica? Is nucleation catalyzed by enzymes? What is the role of pentacoordinated
silica?
Questions: Mack Ross, Bruce Simonson.
Attendance was 45. President Hammarstrom adjourned the meeting
at 9:56 PM.
Respectfully Submitted,
Mark McBride, Meeting Secretary
Geological
Society of
Minutes
of the 1329th Meeting, Wednesday,
April 19, 2000
Powell
Auditorium, Cosmos Club
President
Hammarstrom called the meeting to order at 8:01 PM.
The
minutes of the 1328th meeting were accepted as read.
Visitors
consisted of Henry Shaw, Lawrence Livermore Laboratory.
Five
announcements were made:
There were three new members: Fred Block, of
the Office of Surface Mining; Anthony DeSouza, of the National Research
Council; and Sandra Herbert, of the History Department of the
The field trip to the Moorfield Pegmatite is
still scheduled for May 13.
The Council has been discussing the
possibility of a summer social cruise. A
show of hands showed about 15 people showing interest. Watch the GSW web site for further details.
Chip Groat, Director of the USGS, will be
speaking tomorrow at the meeting of the Potomac Geophysical Society.
Don’t park in the Cosmos Club parking lot and
say that you are attending GSW! The
Cosmos Club will try to charge the parking to GSW if you do!
There were no informal communications. The recent lack of informal communications
was officially noted, and President Hammarstrom asked members to get busy.
There were,
as usual, three talks:
The aging of great escarpments - cosmic rays and
geomorphology. Paul Bierman,
Our research addresses the erosional retreat
of escarpments, for which there are several competing theories. Examination of small-scale worldwide maps
shows there are two kinds: arched (i.e. rounded) and shouldered (i.e.
asymmetrical with a sharp crest). Sinuousity
of shouldered escarpments increases regularly with age, possibly because of
restricted drainage areas. Sinuousity of
arched escarpments increases faster but less regularly with age.
To shed more light on these processes, the
speaker visited the hyperarid Namib Desert, the Great Namibian escarpment, and
the adjacent Namibian highlands of southwestern
Fifty-seven paired analyses of 10Be
and 26Al in samples of bedrock primarily from inselbergs, of
sediment from dry river and stream channels, and of quartz clasts from desert
pavements reveal large inventories of these cosmogenic nuclides. This implies significant landscape stability
over the past million years. Fission
track data extend the erosion rate estimates back in time, suggest similarly
low rates of landscape change, and imply that in general erosion rates have not
changed significantly over >107 years.
Thirty-nine bedrock samples collected in
three transects from the coast, across the escarpment, and into the highlands,
show no spatial pattern in nuclide abundance despite a difference in mean
annual precipitation between sample sites at the coast (<25 mm/year) and
those in the highlands (>200 mm/year).
Average model erosion rates above the escarpment (3.4±1.7, n=6) are
indistinguishable from average rates below the escarpment (3.6±1.9, n =33).
Sediment samples (n=3) from small streams give similar results and suggest that
a basin in the steep escarpment zone is eroding several times faster (16 m/My)
than either a basin in the highlands (5 m/My) or a basin in the coastal plain
(8 m/My). Data from large rivers (n=3)
constrain erosion rates, averaged over 105 years and 104
km2, between 7 and 9 m/My, consistent with rates estimated by
fission track analysis. Small quartz
clasts (n=12) collected from four desert pavements record extraordinarily long,
variable, and in some cases complex exposure histories. Simple 10Be model ages are as high
as 1.8 My; minimum total histories, considering both 10Be and 26Al
and including both burial and exposure, exceed 2.7 My. The pavement on which clasts have the highest
nuclide abundance is located just at the base of the escarpment. The pavement within the escarpment zone is
least stable; all three clasts have indistinguishable exposure histories and
isotopic data are consistent with steady erosion of the pavement at about 2
m/My.
The similarity of erosion rates calculated
from 10Be analysis of fluvial sediments and fission track analysis
of rock suggests that steady state is a reasonable description of the Namibian
landscape over large spatial and temporal scales. At a smaller scale, it appears that the
northern boundary of the massive
Earlier, King had proposed a classic model
that the escarpment had retreated steadily and rapidly. Data from this study do
not support this model; rather, the cosmogenic and fission track data suggest
that the escarpment is retreating very slowly, if at all.
Questions:
Chip Walker, Bill Jennings, E-an Zen, Moto Sato, and George Selden.
Focused ion beam microscopy (FIBM) is a new
tool for examination of geological materials that has been derived from the
microelectronics industry. It has many
features in common with scanning electron microscopy, but, instead of using
electrons, uses a focused beam of gallium ions emitted by a tungsten
filament. Electrostatic rather than
magnetic lenses are used because of the heavier ions, about 186,000 times
heavier than electrons. Each gallium ion
has momentum about 356 times as great as that of an electron. The beam can be used to excavate surface
materials by “sputtering”, or else can deposit materials on the surface, for
example metals used to dissipate local charges.
One application is cutting holes in specimens
so we can look inside. For example, we
can cut a trench in surface and then polish its surfaces for examination. We can also cut thin wafers, down to a
thickness of about 100 nm, and remove them for examination by transmission
electron microscopy. The process is very
controlled and observable, so wafers can be cut from precisely known geological
contexts. X-ray diffraction studies show
minimal surface damage from this process.
The process is very fast; for example, transmission electron microscopy
specimens of diamond can be obtained in about 2 hours rather than 2 weeks as
required for other methods.
FIBM has so far been found to be excellent
for framework silicates, diamonds, single-chain silicates, and it is probably
good for most other minerals. Also, we
can do localized microprobe analyses. It
is not as good as other methods for trace elements, but appears to work well
for the major elements. It provides rich
compositional information at very fine resolution.
Questions: Rhonda Stuart, Naval Research Lab
The geometry of
One of the most important components of the
magmatic plumbing system of Kilauea Volcano is the shallow (2-4 km deep) magma
storage reservoir that underlies the volcano’s summit region and supplies magma
to the East Rift Zone where recent eruptions have occurred.
Nevertheless, the geometry (shape and size)
of
Temporal variations of Pb, Sr, and Nd isotope
and incompatible trace element (e.g., La/Yb and Nb/Y) ratios of
The systematic temporal variations in lava
chemistry at
This discrepancy can be explained if the
volume calculated from lava chemistry represents the hotter, molten core of the
reservoir in which magma mixing occurs, whereas the volumes estimated from
geophysical data also include portions of the reservoir¹s outer crystal-mush
zone and a hot, ductile region that surrounds the reservoir. Although the volume estimate is small, the
amount of magma stored within
Questions:
Bill Melson, Dick Fiske, George Helz
Attendance was 57. President Hammarstrom adjourned the meeting
at 9:55 PM.
Respectfully Submitted,
Mark McBride, Meeting Secretary
Geological
Society of
Minutes
of the 1330th Meeting, Wednesday, May
10, 2000
Powell
Auditorium, Cosmos Club
President
Hammarstrom called the meeting to order at 8:00 PM.
The
minutes of the 1329th meeting were accepted as read.
Visitors
consisted of Sue Webb,
Four
announcements were made:
One new member, Edith Alison, was announced.
A special AGU session was announced by
Katherine Johnson.
The spring field trip will be this Saturday.
A moment of silence was observed in
recognition of the death of Dave Gottfried.
He was a member of GSW from 1952 into the 1970s.
There were no informal communications.
There were, as usual, three talks:
Squeezed out or sucked in?
Characterizing melt flow in the anatectic zone. Nathalie Marchildon,
Ms. Marchildon addressed the basic question
of segregation and migration in partly melted crust; in other words, how is a
felsic melt exported upward from zones of melting deep in the crust?
She presented field and petrological
observations on the nature of layer-parallel leucosomes [the light-colored patches, in other words] in late-tectonic
migmatites in the contact aureole of the Onawa pluton, central
Based on these observations, she proposes a
model for layer-parallel leucosome formation by differential stress-driven melt
segregation from less competent, mica-rich layers, to more competent
quartzo-felspathic layers, leading to layer inflation by melt inflow, rather
than segregation of melt in shear or tensile structures. [This seems to mean that the soft stuff gets squeezed out of the weak
parts of the melted rock and into the stronger parts.] Syn-anatectic contractional folds in part
controlled the patterns of melt migration to the leucosomes. Variable proportions of unmelted material
initially present in the leucosome layers, of melt added to these layers and
minerals crystallized from this melt, and of melt lost from the layers to
external sinks explain the variability in layer-parallel leucosome compositions
in these rocks.
Questions by Jane Hammarstrom, Bill Burton,
and Cy Galvin.
The effects of recharge, geologic setting, and regional water use
on groundwater flow: A case study at
Dover Air Force Base,
Hydrogeological investigations at Dover Air
Force Base,
Continuous recorders on wells and surface
water bodies show the effects of irrigation and of off-Base mining of sands and
gravels. In the southern part of the base, hydrographs of water levels in the
Frederica aquifer show that irrigation south of the base lowers the
potentiometric surface in this aquifer to about 1.5 m below sea level. West of the base, the sediments of the
surficial aquifer are mined for sand and gravel. A dredge mines from one pond a slurry of
water, sand, and gravel. This slurry is
sent to a processing plant, where the sand and gravel are separated from the
slurry and the water is discharged into a different pond. Dredging can produce differences in level of
as much as 4 m between nearby ponds.
Hydrographs of the water levels of the ponds and of water levels in
adjacent wells show that a 3 meter change in the surface-water level results in
about a 2 meter change in the water table at wells about 100 meters from the
pond. Numerical simulations of this
mining shows that near the boundary of Dover Air Force Base, this mining can
reverse the water-table gradient.
Additional problems being investigated
include chlorinated solvents and fuels in groundwater..
Questions by Bill Burton, E-an Zen, and
Dallas Peck.
Hotspots, earthquakes, and the evolution of
the
The
Earlier activity associated with the hotspot
was formerly to the northeast of
Energy and magma from the hotspot drives
Societally, we must consider the odds of
future earthquakes and volcanic eruptions and manage these lands based on
realistic scenarios of such disasters.
Questions by Moto Sato, Jamie Allen, Bill
Burton, and George Helz.
Attendance was 64. President Hammarstrom adjourned the meeting
at 9:50 PM.
Respectfully Submitted,
Mark McBride, Meeting Secretary
Geological
Society of
Minutes
of the 1331st Meeting, Wednesday,
September 6, 2000, Powell Auditorium, Cosmos Club
President
Hammarstrom called the meeting to order at 8:00 PM.
The
minutes of the 1330th meeting were accepted as read.
Visitors
consisted of: Andrea Johnson, Joint Oceanographic Institutions; Roberta
Rudnick, University of Maryland; Bruce Campbell, Air and Space Museum; Forrest
Pike, Bureau of Energy and Minerals, Jeffry Burns, National Research Council;
Ione Taylor, USGS Reston; and Al Taylor, independent oil and gas
explorationist.
Five
announcements were made:
We would like members to help recruit new
members – particularly focusing on students and members of AAPG.
Thanks to Mike Wise and Bill Burton for the
excellent field trip to the Moorfield Pegmatite last spring. Photos of this trip are at the back of the
room and on GSW’s web site.
The fall field trip will be Saturday, October
21st. It will be in the DC
area (exact location not yet set), and is intended as a memorial to Jim
O’Connor.
Teachers at
Earth Science week is coming up.
There was one informal communication by Jane
Hammarstrom. She described her summer
field work on the Salmon River,
There were three formal presentations:
A Quaternary history of aeolian sediment mobilization in the
The
Swezey’s
research investigated these issues. He
worked in the area of the Chott Rharsa, a playa located in western
Thermoluminescence
dating of quartz grains showed that a thick sedimentary section in the area,
which included interbedded lacustrine deposits as well as aeolian sands, had
been deposited within the last 15,000 years.
The Chott Rharsa record and earlier aeolian strata fit fairly well with
previously established Saharan stratigraphy, and show millennial-scale
responses to climatic influences
Questions: Dan Milton, Jan Hammarstrom, Moto Sato, and
Suzanne Weidman.
Experimental evidence on the behavior of gold in magmatic-hydrothermal
systems. Mark Frank,
Frank’s research centers on simulating
conditions within hydrothermal systems that contribute to gold transport and
deposition. He began by looking at
conditions inferred from the Ginzberg Complex, a very large and rich porphyry
gold deposit in
The experimental brine was 70% concentration,
and consisted of NaCl + KCl + HCl + H20. The melt was granitic in composition. Experiments were conducted at a temperature
of 800 degrees C and a pressure of 100 MPA.
The materials were enclosed in a gold capsule, which also served as the
source of dissolved gold. Each
experimental run included two capsules, one brine-rich and one brine-poor. The resulting glass was analyzed using neutron
irradiation analysis for Au and Cl, and electron microprobe for major elements.
Results showed that inclusion-rich glasses
were elevated in Au and Cl. Au was much
enriched when Cl was greater than 10,000 ppm in the brine. It was concluded that gold was transported in
the brine as chloride complexes, as AuCl at chloride concentrations less than
10,000 ppm, and AuCl2 at greater concentrations.
Questions: Jane Hammarstrom, one
unidentified, Moto Sato, and Pete Toulmin.
From Boundaries to Barrels - Sequence Stratigraphy and Oil
Potential,
Sequence stratigraphy is being applied
successfully to oil exploration on the North Slope of Alaska. Sequence stratigraphy is based on the
recognition of packages of sediments that are enclosed within boundary
surfaces, which are unconformities and their correlative conformities.