End of Ice Age

[IceAgeCivilizations]

Laika admitted that granite can cool quickly, as water is involved, as I cited, so no great depth is necessary, next.

 

[Laika]

Laika admitted that granite can cool quickly, as water is involved, as I cited, so no great depth is necessary, next.

I cannot recall doing such. Perhaps you could use the quote funtion to show me.

 

[IceAgeCivilizations]

Poor Laika.

 

[Laika]

Sure. Poor me. And yet still no elaboration is forthcoming.

 

[IceAgeCivilizations]

Laika, go read the posts, skin man pointed the issue out, and/but I did provide evidence to the contrary, which you agreed with, now go figure that bad boy out.

 

[Laika]

Ok, I've re-read the posts. I'll summarize the issue here. If you have any intellectual integrity I imagine you will point out where I've erred. If not, I expect you to continue to dodge my questions.

I brought the presence of granites in the Himalayas into this thread because I believe that their necessarily long crystallization time contradicts your claim that the mountain range formed within the last 4000 years. When I asked about the granite, you said:

So what that granites take time to cool?

I explained that...

the fact that granite crystallizes slowly means that it forms deep underground. If it was extruded, or intruded at shallower depth, it wouldn't be granite. Therefore, the granite which is today exposed in the Himalayas cooled slowly, at depth. This inescapable fact appears to contradict your claim that the Himalayas formed within human history.

To which you replied:

Granitic plutons cooled with much associated water, from country rock and from below, so the cooled edges of the plutons cracked, allowing water penetration into the pluton for deeper cooling, and the heated country rock with water caused steam pressure to crack the country rock, hence the rapid emplacement and cooling of granites.

I think that this is the crux of the matter. My position is that if infiltration of water had allowed the felsic magma to cool rapidly, then the resultant rock would not be granite. It would be more fine grained and, as such, would be rhyolite or something intermediate (the felsic equivalent of dolerite escapes me right now - if indeed there is a term for it).

When I explained my position, you said:

Laika, you said that "the fact that granite crystallizes slowly means it must have been at great depth."

Etna, Santorini, Turkish acccouts of volcanically active Caucasus when Sargon was there.

I'm not sure if the latter part pertains to this subject or to my request for evidence of massive volcanism 3500 years ago. Anyway, the former part didn't add much.

You then added:

Hey Laika, you're wrong about granites, but let's see how you do on pillow basalts, were they extruded into water or onto dry land?

You didn't explain how I was wrong about granites, but I answered that...

Pillow basalts form when lava is chilled rapidly. This usually happens when the molten material is quenched in water.

So far I have not contradicted myself, as you would later claim I did. Basalt is a mafic equivalent of rhyolite. It is finely crystalline because it cools quickly. When the same source melt cools slowly (deep underground), it forms gabbro. Gabbro is the mafic equivalent of granite. Granite also cools very slowly, deep underground.

This is the situation as it stands. Subsequent dialogue has revealed nothing except my befuddlement and your unwillingness to provide a straight answer. If you think I've misrepresented your argument, please let me know. Otherwise, please explain where I've contradicted myself.

 

[IceAgeCivilizations]

Magma injected into wet country (sediments) rock cools to granite, not necessarily at great depth, and if depth continues to be your issue, then how deep do you think those granites must have been in the Himalayas?

 

[Laika]

Magma injected into wet country (sediments) rock cools to granite, not necessarily at great depth, and if depth continues to be your issue, then how deep do you think those granites must have been in the Himalayas?

You still seem to be missing the point. Felsic magma only forms granite if it cools slowly. If it cools quicky, large crystals do not form, and the resultant rock is not granite. The great depth is only an issue in so far as it allows slow crystallization. As a rule, deep intrusions cool slowly and form coarsely crystalline rocks (granite, diorite, gabbro, peridotite). Rocks which crystallize at shallow depths or on the surface (rapidly) are finely crystalline (rhyolite, andesite, basalt). The fact that rocks in the Himalayas have large crystals (they are granitic) means that they cooled very slowly (at depth).

 

[IceAgeCivilizations]

Water in magma lowers the crystallization temp, and small crystals are found around big ones, so no slow cooling there, and it's the rate of crystal nucleation in the magma, rather than rate of cooling, which determines the eventual size of crystals, so great depth was not needed, and you still haven't answered how deep the Himalaya granites must have been emplaced, according to your position.

 

[SkinWalker]

There's a simple way to end this debate. Ice claims granite can cool fast. He need only supply a citation to geological report that discusses it.

Otherwise, he appears to not have a leg to stand on since the grain size of granite is dependent upon the rate of cooling, a very established and well understood process in geology. Magma that cools fast becomes rock other than granite (Pitcher 1997: 218-219).

Pitcher, W.S. (1997). The Nature and Origin of Granite. New York: Chapman & Hall

 

[Laika]

Water in magma lowers the crystallization temp,

Yes, water lowers the melting point of rock. All magma contains volatiles. Are you saying that the granites in the Himalayas formed from magma that had more, and that stayed liquid at a lower temperature than other granitic magma? Are you actually making this specific claim?

and small crystals are found around big ones, so no slow cooling there,

I don't understand. Could you please explain specifically? Do Himalayan granites show a different crystal texture to other granites, or are you making a point about intrusive rock textures in general?

and it's the rate of crystal nucleation in the magma, rather than rate of cooling, which determines the eventual size of crystals, so great depth was not needed,

I'm not an expert on this, but I'm sure you're wrong. Crystals grow as long as the ions in the magma are mobile. When the rock freezes, crystal growth ceases. Therefore, rocks which cooled gradually display large crystals - like granite and gabbro. Dolerite, for example, isn't finer grained because of a lack of crystal nucleation sites, but because the existing crystals didn't have as long to grow.

and you still haven't answered how deep the Himalaya granites must have been emplaced, according to your position.

Well granites generally form deeper than about 2 km. I imagine the maximum depth is limited by the availability of felsic material rather than by physical conditions, so in continental crust it could be many tens of kilometres. A brief internet search suggests a value at least 10 km for Himalayan granites.

 

[IceAgeCivilizations]

As I said previously, the fact that small crystals are found right next to large ones belies your crystal vision.

 

[IceAgeCivilizations]

Emplacement into wet sediments did result in the geology we see, hydrothermal cooling through cracking enhanced the "rapid" cooling of the granite.

 

[Laika]

As I said previously, the fact that small crystals are found right next to large ones belies your crystal vision.

That's it? You're overturning the whole field of igneous geology with a single, evidence-free sentence?

If you don't provide specifics, then I can't give a proper answer, but I'll give my immediate thoughts.
The crystals in an igneous rock do not come off a production line; there will be some size variation.
Different minerals have different melting points, so form at different rates.
As the rock moves through different pressure/temperature regimes after formation, various alteration minerals can form, which do not necessarily share the texture of the original structure. Perhaps the crystals you are referring to could be explained this way. As long as you continue to avoid giving any details, I can't really say any more.

 

[Laika]

Emplacement into wet sediments did result in the geology we see, hydrothermal cooling through cracking enhanced the "rapid" cooling of the granite.

Clearly I have not been emphatic enough. Granite forms when felsic magma cools slowly. The phrase 'rapid cooling of the granite' contains a contradiction.
If the magma cooled rapidly, it would not have formed form granite.
Now, your cause would be helped if you supplied some evidence for what you say. And I am still keen to know how unconsolidated sediments became lithified over 3500 years of exposure.

When I asked you some time ago about the structures we might expect to see if the rocks were soft when the Himalayas formed, you said:

"Slump and flow structures" are often the foothills of the ranges.

I would still love to hear details of these formations.

 

[IceAgeCivilizations]

This thread is about the End of the Ice Age, so why don't you start a new thread about magmatic emplacements?

 

[Prince_James]

IceAgeCivilizations:

So you can not cite your sources again?

 

[IceAgeCivilizations]

Sure, but it's a topic for another thread.

 

[invert_nexus]

How is it a topic for another thread? Seems to be crucial to your argument about when the ice ages ended.

You're just squirming.
Squirm away little puppet boy.

 

[IceAgeCivilizations]

No bearing whatsover, go back to sleep, butt boy.