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View Full Version : Question for geologists about flysch

12-29-2012, 04:43 PM
Been spending an inordinate amount of time studying and going through a box of old geology books to dispose of and the question of flysch entered my head.

Figured I better ask this before the forum pumpkin date/time group happened.

It appears that intrusions in flysch is a good thing, but intrusions into melange is dependent on what part of the melange the intrusion comes in contact with.

I ask this because SC Alaska has the Chugach terrane (flysch) and part of this is the McHugh Complex (melange).

Is my general understanding of intrusions in flysch and melange essentially correct?

The book that started this is "Ophiolitic and Related Melanges", G.J.H. McCall, 1983, Hutchinson Ross Publishing.

12-29-2012, 06:17 PM
I thought "flysch" was short for the tiny specks of gold in my pan. Happy New Year, Eric!

12-29-2012, 10:29 PM
Well after blowing a mouth full of hot tang through my nose Kurt, figured I'd wish one and all a happy new year also.

12-30-2012, 06:40 AM

Thanks for asking such good questions! and... Happy New Year to all!

Because of your question and a personal need learn more about geology, I scurried off into cyberspace on the quest for an answer...

I found that because of continental drift, that Asian geology is similar if not the same as Alaskan geology. We all new that but have probably not studied Asian geology. Asian philosophers also tried to answer the question of:

"What is good?"

When you ask the question with reference to a "good" intrusion, or goodness in flysch vs melange, the qualities that one might look at will vary.

Because of your question, and my search on the topic, I found a couple of very "good" references on the Chugach. i.e. a study of the potential number of different types of mineral deposits that could possibly be contained there-in. The second reference, a paper written by a Canadian (BC) source on the geology of gold deposits in southern Oregon and Northern California with a section on the geology and formation of gold deposits in and around Juneau, Alaska.



These regions have fascinating geology with millions of ounces of gold production. When I view geophysics from all parts of Alaska, I see hundreds of intrusives. I see intrusives with mineralization. I also see many intrusives with no mineralization. Some are extrusives. Many of these are buried intrusives. In my opinion, it really doesn't matter what the surrounding rock types are. Gold has been found in almost every type of environment. Understanding the environment may have academic value. Whether a tectonic process or sedimentary process, oceanic or continental crust was obducted or subducted may have value on a macro geologic scale.

- Geowizard

12-31-2012, 12:05 PM
Excellent point about goodness. What was I thinking? Is good an absolute, kinda like rocky road ice cream - good, setting your hair on fire - not good. Or is it a comparative thingy: 2dwt a day panning - not bad versus 2 ounces a day panning - real good.

I should have framed the question better. Does flysch present a higher probability of hosting minerals that can be economically recoverable compared to a melange when both have comparable igneous intrusions?

And thanks geowizard for the links over the years. How you keep track of so many is beyond me (well really it's laziness on my part)? I contend that once you quit learning, you start dying and that comes soon enough on its own.

Learning process + open mind = synthesis of new ideas. New idea + scientific method → adding to the body of knowledge → increased profit potential.

Knowledge is tested by application. If it is knowledge, the results are predictable. Incomplete or faulty knowledge can result in your hair catching on fire - not good. So remember, a rocky road is good because it holds back the crowd from our favorite haunts.

Bill Bohan
01-17-2013, 02:30 PM

A flyche melange sequence forms from a wedge of grind between a ocean subduction zone of greater proportion. The scarrier "wedge" of deep marine sediment and skinned basalt travel down the suduction zone to compact into rock of its own nature.
Flyche is probably the non permiable non porous of the two rock types
Melange probably has more of a brecco composition and may be less porous and permiable and jumbled and non stratified .
The more sand than silt in your sequence would probably over all determine your porosity and permiability. If the flyshe melange reached metamorphic depths.....less porous less permiable.

The graywacke in the sequence may have the potential for being metal bearing.