>On Thursday 20th February, Glenn Morton wrote:
>
>"Those who might think that water flow through an overlying rock
>is rapid should realize that water flows about half as rapidly
>through rock as does oil ( Chris Clayton, Differential Flow
>Rates of Petroleum and Water in fine-grained sediments, AAPG,
>sept. 1993, p. 1613) The authors attribute this to the lack of
>unbound water in rocks."
>
>The neocatastrophist scenario opens many avenues for tectonic
>disturbance of rocks, creating channels where none existed
>before. Even without catastrophism, I do not consider that a
>batholith can be emplaced without considerable disruption to the
>country rocks.
>
While this is true, the high temperatures of the water allow them to carry
lots of minerals in solution. As these hot waters rise, they deposit some
of these minerals along the pathways, effectively sealing these passages off
by means of mineralization. Lots of mines chase such mineral veins which
may be only 3 inches wide for a long way. The Molly kathleen Mine in
Cripple Creek Colorado followed one such vein and produced much gold from it.
>GM: "While I can not find a reference, I would be willing to bet
>that groundwater flow in a hydrothermal region, cooling a
>batholith, would still take longer than a global flood could
>accommodate, because water does not travel rapidly through
>shale. Shales have permeabilities of the order of a few
>millidarcies."
>
>Tectonically disturbed shales present a rather different picture:
>the permeabilities will be larger. Furthermore, when people
>start to look for evidences of convection, they are likely to
>find them. Parmentier and Schedl (1981) have considered the
>thermal aureoles of the Mull intrusive complex, the Skye Cuillin
>gabbro, and the El Salvador porphyry copper deposits. The shapes
>of the metamorphic aureoles were inconsistent with purely
>convective heat loss, and yet could be explained by invoking
>convective activity.
I think you mean "inconsistent with conductive heat loss". But once again
as the batholith center betins to cool it is not in convective communication
with the surface and is only in conductive communication with a convective
system.
--------------------------
region of water convection
----------------------
region of conduction
------------------
molten lava
>First, I am not defending the idea that batholiths are all cooled
>within one year: I am promoting neocatastrophism. Second, I
>have already indicated that a variety of mechanisms may be
>relevant: convective cooling and alternative models of granite
>emplacement. In addition, I am sympathetic with the expanding
>earth concept - which has thermodynamic implications which favour
>rapid cooling.
I know I used to advocate that view but measurements by large base-line
radiointerferometry have destroyed the concept of earth expansion. For
those that don't know what we are talking about. the fellow who initially
suggested continental drift in the modern form, S.W. Carey, ended up
rejecting continental drift in favor of earth expansion about the time that
all geologists were accepting continental drift. He wrote an excellent
book, published by Elsevier in their Developments in Geotectonics series.
Now back towhy expansion is false. See "Studying the Earth by Very long
Baseline Interferometry," Scientific American November 1986, p. 46
>Again, it is not my intention to fit all the cooling into "a
>single year". But are your points about crystal sizes
>substantive? I accept that this is an area where quantitative
>measurements are needed. Sure there are time implications - but
>how much time? Dowty (1980) cites maximum rates of crystal
>growth in a granite melt with 3.5% water as:
>quartz 1.0 x 10^-8 cm/s
>alkali feldspar 1.0 x 10^-7 cm/s
>plagioclase 1.0 x 10^-6 cm/s
>(Note: dry granites have higher growth rates).
>The number of seconds in 1 year is 3.15 x 10^7. When compared
>with the maximum growth rate parameters for wet granitic melts,
>there are implications for time: large crystals need not imply
>time intervals much greater than a single year. Luth (1976)
>comments:
> "It is frequently assumed that the presence of large
>crystals in these phases implies slow growth over long periods
>of time. Although this may be the case, the intent here is to
>demonstrate that it does not necessarily hold" (p.405).
>
If I can remember, let me talk to a couple if igneous experts at work and
see what they say about this. I hate mineralogy and probably can't go much
further on crystal size on my limited mineralogical knowledge.
>Regarding the Oceanic Ridge systems:
>DT:
>>... I cited the oceanic ridge systems:
>>buried several kilometres down, but with enormous water
>>convection cells cooling them. The amount of water moving
>>through the oceanic crust is enormous. Conductive heat loss is
>>negligible compared with convective loss.
>GM: "Can you give me a source for how much water flows through
>these systems? I just looked and couldn't find one. What does
>enormous mean?"
>
>Edmond et al (1982) suggest that "a volume of water equivalent
>to the whole ocean must circulate through the high temperature
>intrusion zone in the ridge axis ... every 8-10 Myr".
Do you know how much sodium is removed by these circulations? I know that
lots of the elements deposited in the oceans by rivers are removed by
chemical reactions in the MORBs but I can't find a good number on sodium.
An extraneous question. Do you know how many kilometers are in the trench
system? I have been looking for this value for about 6 months and can't find
it. Even the USGS didn't know, which amazed me. Ineed this value.
>
>Macdonald et al (1980) estimate that a single vent provides a
>hydrothermal heat loss of (6+-2) x 10^7 cal/s. This is compared
>with the conductive heat loss over a 60 square kilometre area of
>0.23 x 10^7 cal/s. The heat flows are so high that the authors
>estimate the vents are active for less than 10 years. This study
>"emphasises the importance of hydrothermal activity in the global
>heat budget".
>
>Cann and Stiens (1982) argue that the heat source for black
>smokers must be magma chambers - nothing else will satisfy the
>modelling constraints. Large sulphide deposits require the
>crystallisation of large volumes of magma. If larger deposits
>have to be formed, more black smokers can be invoked and there
>can also be replenishment of the magma chamber. Thus, three
>black smokers could produce a 1 million ton ore deposit in 320
>years, solidifying 7 cubic kilometres of magma in this time. One
>black smoker is said to have a mass flow rate of 160 kg/s.
>
>[Note: even though these timescales are geologically short, I am
>of the opinion that they are unrealistically long. I say this
>after visiting some of the Cyprus sulphide deposits and comparing
>them with what we know of the present day deposition of
>sulphides. The latter are quite minuscule in comparison: there
>are no adequate modern analogues for producing 1 million ton
>deposits. We need catastrophist mechanisms and models.]
>
>Anderson et al (1979) say "By carefully measuring the
>nonlinearity of temperature profiles, we have calculated both the
>conductive and convective components of the total heat flow at
>the sea floor. Significant convective heat transfer is occurring
>through the crustal and sedimentary layers even at the oldest (55
>x 10^6 years) experimental site".
>
>For a popular overview, see Macdonald and Luyendyk (1981).
>
>Regarding models of batholith formation
>DT:
>> ... Large magma
>>bodies moving upwards through the crust of the earth have the
>>problem of "What creates the space into which they move?"
>GM: "melting and incorporation of the rock into the magma. as
>well as uplift. Mt. St. Helen underwent an uplift and even an
>expansion of the mountain prior to its eruption."
>
>Are you serious?
Yes I am serious, In 1980 I was in charge of hiring and training
geophysicists for Atlantic Richfield Oil Co. I tried to hire a summer
student who was doing a Ph.D. at the University of Washington, Seattle. I
have forgotten his name. Mt. St. Helens began shaking in March this guy was
supposed to report to work on June 1. On Friday, May 16, 1980 this fellow
called me a told me he could not come to work for me because he was doing
his work on the volcano and it was a once in a lifetime opportunity. As we
chatted, he told me that he needed to go up to the mountain and replace his
film in the cameras he had set out. His project was time-lapse photography
of the mountain. He had a camera which took pictures of the dome every few
hours. On Sunday morning, when the volcano blew up, I heard that a couple
of guys had died on the mountain, I was afraid it had been that fellow
because of our conversation. On Monday I called him to see if he was alive.
He was. He had gone to the mountain on Saturday, less than 24 hours before
it blew, and retrieved his film. He said that the mountain was shaking like
a leaf that Saturday. He said, he changed his film and got back into the
helicopter as rapidly as he could. He admitted that he had been very scared.
When I wnet to Seattle the next Fall for recruiting, i went to his office.
he showed me the photos he had taken from March to May 17. I couldn't see
a differece and told him so. He then put the march picture under the May
picture and placed them on a light table so that you could compare them.
Like a balloon, the mountain had expanded several meters horizontally. So
yes I am serious.
>How much country rock do you think a magma body
>can ingest before it becomes too cool to melt it? Remember that
>granitic magmas are far cooler than basic magmas. Stoping will
>not get you very far! And where is the physical evidence for
>extensive stoping? We do see xenoliths - but they are hardly a
>major component of batholiths. Regarding Mt St Helens: how much
>uplift are you prepared to defend? A few metres? If you want
>much more, you are moving into the domain of tectonic emplacement
>- which will disrupt the surrounding rocks and create channels
>for water flow.
I have no doubt that water could flow through the cracks that must have
existed in the rocks of St. Helens. But you have still not dealt with the
conductive zone which grows as the magma chamber cools. The solid lava rind
will not have cracks through which water can flow. On a mile wide
batholith, as it cools, the water will not be able to flow to the actual
lava chamber.
>It may be apparent by now that my references all date from 15
>years ago (the last time I set out to research this area). I've
>retained an interest in the subject - and nothing I've seen in
>the intervening years has suggested to me that I'm on the wrong
>track. Perhaps it is now appropriate to look at the topic area
>again - but I would want to build on the kind of thinking I've
>expressed in this post and not on the old orthodoxies.
It has been a while for me also since I have delved into this issue.
thanks for the very interesting discussion.
regards,
glenn
Foundation, Fall and Flood
http://www.isource.net/~grmorton/dmd.htm