Evidences Of Diverging Processes Within Tibet Mountain System.

  Navigate to "Lhunze" using a map tool, set it to "Terrain" mode. The valley spans approx 20km from West to East (and slightly from North to South). The width of the valley is approx 3km. Northern "shoreline" (so to say) of the valley reflects the southern "shoreline" quite nicely. The diverging process, I think, took place.

   The diverging process was rather local.  On further examination of Tibet mountain system we could find many other instances of a diverging processes. Could the pattern had been caused by the global process of the collision between two continents? I am not sure it could. 

   Rather, as I suggested in "Formation Of Mountain Ridges by Broken Process Of Subduction Of A Tectonic Plate." ( http://divergent-boundaries.blogspot.com/2011/05/mountain-ridges-formation-keeping-it.html ) and "Flood basalt" ( http://divergent-boundaries.blogspot.com/2011/07/flood-basalt.html ) the assembly of loosely coupled chunks of crust would react on local extension forces by performing local "forced diverging processes". Also a divergent boundary (even local one) could develop the spreading force if deformations and temperature gradient were present.

   If rifts are found along the center-line of a valley, then, I'd like to think, the diverging process was not smooth, the diverging force was partially of fully developed by the boundary itself as it was described in my previous posts. If the floor of a valley is smooth, then I'd like to think the diverging process was caused mostly by external forces.

   Talking about Lhunze, I'd like to conclude, that the position of the inclined chunks of crust within the local assembly is that, they look East (and slightly South). That is, the vector perpendicular to the plain of the piece of crust would point to East (slightly South) and to somewhat bottom due to the inclination. Recall "Reshaping Pangaea" ( http://divergent-boundaries.blogspot.com/2011/07/reshaping-pangaea.html ), the crust here went from South-East. One or two chunks (whatever fit 20km) due to local extensional forces got broken and diverged off the break-line. Neighbouring chunks, as the chunks within the assembly are loosely coupled, did not broke and did not diverge, that's why the valley developed locally. If it were the global force of the collision between two continents to form the mountain system, I don't see how the local divergent boundaries could had developed.
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Flood basalt.

1. Old crust breaks into pieces, new crust subducts under it. Magma gets locked.
   Once the subduction of the oceanic crust started, the newly spread crust is easier to get subducted compared to the crust that was developed by spreading against non-subduction borders. Current Atlantic ocean crust is not as smooth and thin as most of Pacific ocean crust. That's why when The Ring OF Fire had shrunk and the continents decided on getting back through Atlantic, the current Atlantic crust would not get subducted, it would rather be getting broken into chunks, and the chunks would take inclined position. The newly spread crust being smooth and thin would be able to get bent and dive under the chunks of old crust. The magma below the broken chunks of older crust is getting locked by the subducting plate.
2. Overlapped subducting plates uplift the locked volume of magma. 
   The Ring Of Fire is shrinking. Subducting plates are getting overlapped. One plate's performing shallow subduction, the other's doing steep subduction. The resulting deep structure is less dense than surrounding magma, thus the locked volume of magma is getting uplifted.
3. The diverging process squeezes the locked magma out.
   The uplifted ridge is getting broken by gravitation assisted diverging process due to the boundary deformations between the two plates. The diverging process squeezes the locked magma out and down from the volume. Probably The Snake River Plain could be a good example of the process. The overlapping plates had locked magma under it and had uplifted it. The thick structure of overlapped plates did not melt for quite long time and had reached as far as Yellowstone. The diverging process naturally squeezed out the magma down on both sides - Columbia river and Great Basin flood basalt. The process on the tip of the overlapped plates would cause a stream of magma and thus would be forming calderas from time to time.
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Porphyry Copper. More On Reshaping Pangaea (Gondwana).

Today's documents are:
- U.S. Geological Survey, Open-File Report 2005-1060, Version 1.0. "Porphyry Copper Deposits of the World: Database, Map, and Grade and Tonnage Models" By Donald A. Singer, Vladimir I. Berger, and Barry C. Moring, 2005. ( http://pubs.usgs.gov/of/2005/1060/ ) [Accessed Jul-22, 2011}

- NASA, Earth Observatory, "Alfred Wegener (1880-1930)" by Patrick Hughes, map on Wegener's fossil and geological evidence that the continents were previously connected ( http://earthobservatory.nasa.gov/Features/Wegener/wegener_4.php ) [accessed on Jul-22, 2011]

- "Some General Concepts underlying the Science of Geology", primary author Nicholas M. Short, Sr. , section 2, "The Rock Cycle" ( http://rst.gsfc.nasa.gov/Sect2/Sect2_1b.html ), image showing the positions of the continents from early Pangaean breakup to the Present. [accessed on Jul-22, 2011]

Only Eastern Australia is rich of porphyry copper deposits.
   On the image showing the positions of the continents from early Pangaean breakup to the present there is no porphyry copper deposits for:
- southern part of South America;
- Africa (3 deposits in Africa are too old to fit the discussed time frame);
- Antarctica;
- India;
   Only Eastern Australia (New South Wales and Queensland) are rich of the deposits. The deposits are dated according to mentioned "The tab-delineated text file containing the porphyry copper database", if I understand it correctly:
- 220-300 Mya for Queensland deposits (approx 16 items);
- 440-460 Mya for New South Wales deposits (approx 8 items);
   Also half dozen of deposits are scattered between Western Australia, Victoria, South Australia, the deposits seem to be too old to fit the discussed time frame.
   How did all items of the image managed not to develop porphyry copper and only Queensland and New South Wales got the copper during 220-300 Mya and 440-460 Mya accordingly?

Comparing the shorelines.
   Let's look a bit closer at Queensland/New South Wales shoreline using a map tool. Compare the shoreline to the Chile's shoreline corresponding to Atacama desert. Compare the Australia's fragment between Byron Bay and down to south of Port Macquarie to the Chile's fragment between Arica and down to Tocopilla. Please keep in mind, Australia may had rotated slightly since then. I can be wrong, that's just a suggestion that Australia once was connected to South America. Besides the fragment of Chile's shoreline seems to be complimentary to the mentioned Australia's fragment, Chile, as everyone know, features porphyry copper deposits not even worse than East Australia.

 The porphyry copper pattern as an evidence of the layout of Pangaea.
   I'll check Chile's deposits ages later, the discrepancy in the age can be explained by the fact that the subduction process on the western and eastern sides between diverging Australia and Chile may had initiated at different times (porphyry copper development seems to be related to the subduction process). The porphyry copper development seems to be taking time of steady subduction of the oceanic crust. The suggested by Wegener Australia's post-Pangaea trajectory seems not to fit the  picture of steady subduction process against the East Australia. The suggested in "Reshaping Pangaea" ( http://divergent-boundaries.blogspot.com/2011/07/reshaping-pangaea.html ) the Australia's post-Pangaea path seems to fit porphyry copper pattern better. 

India's almost "porphyry copper"-less status.
   Regarding India's almost "porphyry copper"-less status, India seemed to start off the Australia's North-West, that is too far from the subduction zone, and thus had had no chance developing porphyry copper.

Summing things up.
   Well, this was an attempt to prove that Australia was connected to South America at Pangaea times. Then Australia was diverged out to its current position. The diverging was accompanied with the subduction of oceanic crust under the Eastern Australia, thus porphyry copper deposits were developed. The 440-460 Mya age of New South Wales deposits was, probably, because the deposits were developed on the previous "Ring Of Fire" cycle.

Next stop - nothofagus-less Africa.
   Next attempt to prove "new" Pangaea layout will probably be to talk on nothofagus-less Africa. On Wegener's layout of Pangaea, nothofagus was found on the left from Africa in South America, on the right in Australia, and even on the bottom in Antarctica, but not in Africa. The suggested in "Reshaping Pangaea" ( http://divergent-boundaries.blogspot.com/2011/07/reshaping-pangaea.html ) "new" Pangaea layout takes care of Africa.
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Reshaping Pangaea.

   Last weeks I've been trying to approach "Basalt Flows" theme. I think, I need to step back and reshape some aspects of the big picture. The idea of this post is to rethink the separation of Pangaea into the continents and how the continents drifted to their current positions.

The documentss/tools used:
- NASA, Earth Observatory, "Alfred Wegener (1880-1930)" by Patrick Hughes, map on Wegener's fossil and geological evidence that the continents were previously connected ( http://earthobservatory.nasa.gov/Features/Wegener/wegener_4.php ) [accessed on Jul-12, 2011]

- "Some General Concepts underlying the Science of Geology", primary author Nicholas M. Short, Sr. , section 2, "The Rock Cycle" ( http://rst.gsfc.nasa.gov/Sect2/Sect2_1b.html ), image showing the positions of the continents from early Pangaean breakup to the Present. [accessed on Jul-12, 2011]

- your favourite map tool, set it to accommodate the whole World, the mode is "satellite".

Optimizing Pangaea initial layout.
    Let's have a look at the mentioned image showing the positions of the continents from early Pangaean breakup to the Present. While the Wegener's reason behind the layout is clear, we need to keep in mind that the Earth is spherical, and therefore the layout can be optimized to keep the color paths shorter and a bit more logically consistent - to minimize flora/fauna needs to overcome the high mountain systems. Just position initially on the mentioned image:
- Australia at the West of South America, the place that roughly corresponds to the current Atakama desert location, Chile.
- New Zealand - again, western border of South America, below Australia.
- India - place its cratons to western Australia.
- Antarctica - place it more North-East up on the Equator.
I am absolutely sure I am not the first who suggested the layout. I'd like to credit the first person who suggested the layout, as soon as I find the info.

Continents drift paths.
    In our approach North and South America motions remain the same to the traditional ones.
    Regarding India, Australia, New Zealand - let's have a look at Google map. Let's take a closer look at the shapes of eastern and western subduction zones. Do not the eastern and western shapes resemble each other? If the oceanic floor on the map between the shapes were cut off the map, would not the shapes fit each other? Had not the shapes been diverged out? Clearly, yes, judging by the East-West rifts on the floor.
Wait, some would say, we can see how South America could cast off India, Australia, New Zealand, but how did it manage to cast off the "forward-running subduction zone"? Well, that's the theme for another posting.
    Now we see how the tremendous amount of the assorted stuff had been pushed towards the location now known as Tibet/Himalaya. The stuff eventually was locked by India's deep-rooted cratons, and the incoming and subducting plates had had no choice to escape the location when getting semi-molten and therefore, the choice other than to be pushing up the gigantic cluster of mountain systems.
    Antarctica and later, the divergent Indian ocean floor blocked the mentioned above stream of the assorted stuff from propagating westward to Africa.
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edited Aug-17, 2011.

Static volume of hotter magma under the crust is likely to be the effect of the process in the above crust.

   One of the next posts will be on Basalt Flows. The post is expected to be somewhat lengthy. To make it shorter let one concept to occupy separate (this) post. The concept relates to the previous post "Ridge Push, Or Bridge Over Troubled Magma." ( http://divergent-boundaries.blogspot.com/2011/05/ridge-push-or-bridge-over-troubled.html ). Basically it's about what's the cause and what's the effect - static hotspot or the processes in the crust.

   Traditional Plate Tectonics tells us that basalt flows are the products of the mantle plumes (hot spots). As for me, there are some issues with the concept. Should some hot (and therefore less dense) plume occur in the mantle depth, it wont be upwelling by shortest path. Instead, as the Earth is rotating, the Coriolis effect would make the path to be very curvy, and as the velocity within the stream varies greatly, the stream would get "blurred", that is, it would have to get mixed with the magma it penetrates through.

   In other words the plume stream (should it occur) has to mix with magma it gets through, and the length of the affected area has to be comparable to the distance the stream had made, that is it has to stretch by thousands kilometers. The temperature within the volume will be only slightly higher than the temperature of the neighboring magma. And, instead of trying to penetrate the crust, the volume would rather keep on its movement.

   In other words, if the volume is not moving, then the hot spot's nature has nothing to do with magma depths. Its nature belongs to processes that are taking place right in its ceiling - oceanic crust. Again, in other words, static volume of hotter magma is unlikely to be the cause of what's happening with crust, rather the static volume of hotter magma is likely to be the effect of the process in the above crust.

   I think, more practical research should be held on the hot spots. The articles below, as for me, cast some doubts on Hawaiian volcanoes to be the effect of a mantle hotspot.
MIT News, "Hotspot in the hot seat. New seismic imaging alters the picture beneath Hawaii" by Jennifer Chu, MIT News Office, May 27, 2011.  ( http://web.mit.edu/newsoffice/2011/hawaii-hotspot-0527.html )
Science, "Another Look Beneath Hawaii Knocks Islands Off Their Riser Pipe" by Richard A. Kerr, 26 May 2011. ( http://news.sciencemag.org/sciencenow/2011/05/another-look-beneath-hawaii-knoc.html )
   The assumption that "static volume of hotter magma under the crust is likely to be the effect of the process in the above crust" is crucial in many Plate Tectonics topics, to name a few: the mechanism behind the diverging boundaries, intraplate diverging processes, basalt flows, some types of calderas (Yellowstone), etc.
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edited: Aug-17, 2011

Diverging Processes Within Las Vegas Valley.

   Let's navigate to Las Vegas. Set the map to "Terrain" mode. See the part of Las Vegas Valley between North-West of Las Vegas and Indian Springs which is further North-West approx 50km. Would not north-eastern mountains of this part of the valley fit south-western mountains if the part of the valley were cut off the map? I'd say, yes. If the depths of the mountains were found of different stuff and age than the depths of the valley floor, then the mountains were diverging. The valley's floor, I'd expect to be of magmatic nature that a divergent boundary usually consist of. The mountains I'd expect to be gathered of chunks of older oceanic crust and therefore even at the depths they should show all the usual oceanic floor features.
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