I directed you to a paper arguing for a strike-slip subduction transition, you must provide me a paper arguing for a subduction reversal at the Puysegur trench. That's how science works. Oh yes you do. You make the vague claim that the rotations around Euler poles for the Pacific plate and the Australian-Indian plate explain the variability of the tectonic boundary across New-Zealand (eastward subduction, strike-slip, westward subduction), you support your claim with data or papers. The rest is blah-blah. Buoyancy. This comment is irrelevant to my statement. I was referring to the orthodox view of plate tectonics: knowing that the density of the oceanic crust is dependent on its age, then it was thought that the dip of a slab would be related to its age, the oldest, the densest, the steepest. This is not the case as shown by Serge Lallemand. The dip is more dependent on other parameters, especially the global subsurface mantle flow (See Carlo Doglioni). Indeed, you're nowhere to be found in the scientific bibliography databases. You have a master degree but what makes you believe that you have more credentials than professional researchers?
You're welcome, but obviously, you're much more knowledgeable than me for this particular subject. Please Register or Log in to view the hidden image! The two-stage emplacement history for Arizona kimberlites is very interesting. Thank you for citing it.
No, and no - I've already told you where the data is, look at any reconstruction, the evidence is right there. I'm well aware of the standard view, thankyou very much, seemingly more so than you. You seem to fail to grasp how bouyancy is important. You're at least aware that Bouyancy is tied to denisty, right? What do you think is going to happen when a piece of oceanic crust with bouyant continental crust riding on it (or with it) encounters a subduction zone hmm? Orthodoxy preaches that it depends on the relative net densities of the two pieces of oceanic crust. If the over riding crust is young enough, the continental crust will be emplaced on it. However, if the over riding crust is old enough, then the net density of the subducting plate will be reduced sufficiently to cause a reversal in polarity of the subduction zone. For a start off, I'm discussing subjects in a field which I actually crosstrained in. Secondly, I at least can say that I understand the role that relative crustal bouyancy has to play in plate tectonics.
No you did not provide any scientific paper supporting your claim of subduction reversal at the Puysegur trench. By contrast, I provided a scientific paper supporting a strike-slip subduction transition : Lebrun et al (2010) Tectonics 19, p688 I provide an accurate reference, you only make vague statements. That makes all the difference. So you are pretentious enough to teach me what is buoyancy when you can't even spell it right? Please Register or Log in to view the hidden image! You know that whatever its age, oceanic crust is always denser than continental crust do you? Over riding oceanic crust? For the reader, could you please explain how a subduction reversal happens in a clearer way? For example You could make a step by step description of the scheme I provided earlier :http://www.gly.uga.edu/railsback/DPT/SubductionReversal02.pdf You do truly believe that you are more experienced than professional researchers like Mazumber, and even enough to accuse him of "cherry picking". You definitively lack of humility.
Don't need to - the proof of reversal and migration is all right there, in any reconstruction of the (appropriate part of) the east Gondwana margin. Meh. A typo. That's the best you can come up with? And yes, I'm teaching you it's use, even if I might have misplet it. Please Register or Log in to view the hidden image! You have nothing better to do than proofread another's arguments? Are your scientific arguments so weak that the best that you can come up with is to nitpick the spelling? This contradicts nothing I have said - remember, I talked about the net (or average) buoyancy (or density) You do know that subduction zones occur where oceanic crust meets oceanic crust, right? According to that schema the plate on the right (the subducting plate) is subducted under the plate on the left (the over-riding plate) until the net density of the subducting plate is less than the net density of the over-riding plate, at which point a reversal occurs. Now it's your turn - do you understand how having less dense crust incorporated in, or on top of the subducting plate at the point marked 4 might result in either a polarity reversal, or the crust becoming welded onto the over-riding plate, depending on the relative densities? Are your arguments so weak that the best you can hope for is to appeal to the authority of others? Seriously. The point you fail to realize is that I don't neccessarily need to be more experienced than them to be able to critically assess their work, and recognize logical fallacies for what they are. I understand the principles of critical reading and critical thinking, and how to apply to them to work such as that done by Mazumder. That you would even consider posting this is so mindboggling I'm literally... Gobsmacked doesn't even come close to covering it. It's an ad hominem argument. It's an appeal to authority. It's a strawman hypothesis. It's a bait and switch. And it's up starts like me, capable of critically reviewing what they're presented that lead to breakthroughs.
Here's proof that half of what I said is true. Of course, it requires the realization that mainstream theory assumed that margins are dynamic (as opposed to the static assumption you seem to be assigning to it). http://www.utdallas.edu/~rjstern/pdfs/SternEPSL04.pdf Stern argues that the subduction observed in the Puysegur trench is an example of induced nucleation of a subduction zone - he argues that because of how close the pole of rotation is to australian-pacific boundary in that area, that small changes in the location of the euler pole can (or will) result in large changes in the nature of the boundary. He argues that a shift in the Euler pole caused by the reorginaztion of the plate boundary resulted in the nucleation of a new subduction in what was a transform fault. This: Please Register or Log in to view the hidden image! Is the WBZ that he is referring to (or part of it anyway). EG: Note the moment-tensor solution here is predominantly thrust. So the second part of my assertion is proven, and verified by a peer review paper. -That subduction occurs in the Puysegur trench. -That the Polarity of the subduction is opposed to that occuring in the Hikurangi trench. Are we clear on that? Your assertion: Is that the strike-slip subduction is there instead of a reversal, my assertion is that it is there because of the reversal I mentioned, and the paper I linked to suggests that it is a neccessary step in the induced nucleation of a new subduction zone. That leaves me to demonstrate the first part of my claim, that prior to this, and in response to some event a subduction zone existed at a different location, and that at that location, the polarity was reversed - IE the pacific plate (or some other plate) was being subducted. However, this involves delving into the causes of the reorganization that Stern alluded to, and my recollection is that it is due to a combination of factors such as the subduction of the Phoenix plate under Eastern Gondwana (which proves the first point I made) and the collision of India with Eurasia (note - I'm not claiming these events were simultaneously, they don't need to be to change the way these plates move in relation to each other). More when I have time (maybe).
Trippy: . . . thanks for the jpeg (your post #66) . . . confirms (to my satisfaction) my earlier discussions on lamproite activity . . . wlminex
And here's the proof of the first part of what I said. Please Register or Log in to view the hidden image! From this website, discussing the cruistal evolution of Fiordland: http://www.lithosphere.co.nz/crustal/index.html Note that the reconstruction (fig. a) has the Pacific and Phoenix plates subducting under Eastern Gondwana, exactly as I maintained it did in reconstructions of the paleo margin. So I have precisely proven my original claims that subduction is occuring in the Puysegur trench, that the polarity of that subduction is opposed to that in the Hikurangi Trench, and that a reversal of the polarity of that subduction (with associated migration) has occured - probably all caused by a combination of the subduction of the Phoenix plate (the spreading ridge stalled outboard of the subduction zone, resulting, I believe in the switch from compressional tectonics to extensional tectonics eg Luyendyk 1995). I'm not sure of the significance, but I do find it interesting to note that there is some overlap between the youngest estimates of when the collision between India and Eurasia occured, and some of the older dates obtained for the alpine fault - but I'm not aware of any researchers currently pursuing that direction. As was alluded to in my previous post, a reorganization of the plate boundaries in this area is ongoing, and it's initial causes seem to be a combination of factors.
Always need to. So far you did not provide any evidence supporting that the strike-slip subduction transition supported by Lebrun et al (2010) Tectonics 19, p688 is incorrect and must be replaced by a subduction reversal. Give me a break! You insinuate repeatedly that I'm too stupid too understand buoyancy and its implications whereas you can't even spell it right, nor describe correctly how buoyancy plays a role in subduction reversal. You are so vague and confusing in your explanation that, for the reader, I have to ask you to use more accurate term like "Over riding oceanic crust" instead of the vaguer "Over riding crust". The funny part is that you don't even realise how vague you are. You should thank me for providing an appropriate scheme to help you formulate a better description of what is a true subduction reversal. But despite of that help, showing the clear change in subduction polarity at the same spot that is required for a subduction reversal, you still persist in your personal erronated interpretation of the Puysegur trench as a subduction reversal rather than a strike-slip/subduction transition as proved in Lebrun et al (2010). Trippy the new Galilea… or not. Come on, you failed at the first level of critical thinking by lacking to address the arguments piled up by Carey (1) , all supporting the Expanding Earth theory in the most clear cut way. see S. Warren Carey 1983 "The Necessity for Earth Expansion" pp375-393 in Carey, SW (ed): Expanding Earth Symposium, Sydney, 1981. Just half? What could be half true in your claim that there is a subduction reversal at the Puysegur trench? that there is subduction but nor a reversal of polarity? Oh, and in case of you miss it again, yes, I'm ironic. I see that you still don't understand that mantle flows induce much more dynamics interactions than simple 2D plates motions. So he's arguing that the proximity of the Euler pole is a good argument for a transition from a transform fault to a subduction zone if the kinematic change, but it the kinematic did not change for 40 Ma according to the Hawaii hotspot track . But wait a minute… he discuss a "transition from a transform fault to a subduction zone" isn't it the same as the strike-slip to subduction transition I'm advocating since the start? OF COURSE IT IS. Thank you for burying yourself! Give me a break! This peer-reviewed paper prove that you were plain wrong with the subduction reversal as it supports a strike-slip to subduction transition. Obviously, if this is a strike-slip to subduction transition, there must be some subduction Who cares about the polarity of Hikurangi trench!!!! We are discussing what happens at the Puysegur trench! And there, there was no reversal of polarity. Bottom line: You faint to not understand what is a subduction reversal. A reversal of subduction at the Puysegur trench would mean that a slab was dipping North-Westward in the past at the Puysegur trench, and that the polarity reverted so that there is now a slab dipping South-Eastward (as shown by your figure). Check back the figure I posted to get it once and for all.(http://www.gly.uga.edu/railsback/DPT/SubductionReversal02.pdf) Sorry, but an hypothetic subduction that would have occurred 100 Ma ago and before a major extension extension episode that involved the whole margin does not count. If you believe you would save your face like that, you were deeply mistaken. But that is yet another illustration that you just can't admit to be wrong. You would just have to say: "OK, I was wrong, there is not a subduction reversal at the Puysegur trench, but a transition from strike-slip to subduction". Errare humanum est, perseverare diabolicum. And all the arguments are similarly biased, showing your inaptitude to sustain an objective scientific discussion. The most ironic part is that you suggest that I'm the one who don't understand what happens! Even suggesting me to go back to the basics like buoyancy effects. That is ludicrous. You won't make any progress as long as you consider me as an idiot and you as a superior mind.
You demonstrate that you don't understand what I actually said. I didn't say that a transition zone was wrong, I said that your assertion that it occurs in place of subduction is wrong. Learn the difference. I didn't say there was no transition, only that subduction is occuring - which I have proven. I care, because it was part of my original assertion. I understand fully what subduction reversal is. The failure is in your ability to comprehend the evidence I have presented you. Incidentally, your own figure contradicts you, because it shows the trench migrating, meanwhile I've provided you with sources that explicitly call the history of the Puysegur trench a subduction reversal, so I really don't know where you're coming from with this. The bottom line is I have proven each of the elements of my original assertion. Again, I find myself repeating: The transition zone exists because the reversal of polarity is leading to the nucleation of a new subduction zone. Yes, it does count. because it was what I was referring to in the first place. What, did you think that I actually meant that subduction had always occured in that location? Give me a break. I'm sick of your trolling. I'm sick of your ad hominem arguments. I'm sick of your assinine attempts at character assasination. Any reasoning, thinking human being can see that I have adequately proven my assertions. We're done here.
You lie. In this post (http://www.sciforums.com/showpost.php?p=2773441&postcount=39), you replied "no it doesn't" to my statement that "The Puysegur trench illustrates a strike-slip-subduction transition, not a reversal of subduction" as shown by Lebrun et al (2010) Tectonics 19, p688. This is a clear attempt to evade the issue. Your sources do not show any subduction reversal at the Puysegur trench which is southwest of New Zealand. It shows a subduction zone 100 Ma ago to the east of New Zealand, that existed before an intensive episode of rifting. So it actually illustrates a subduction to rifting transition (very clear in the paper you cite in reference). You have proven nothing as shown above, quite the apposite. You misspelled "proven your assertions". The reader of this discussion had certainly already corrected. Finally something we can agree on.
Yes, as I have said repeatedly, it was your assertion that it was occuring instead of, rather than because of, that I was objecting to. Just a quick tip: If you're going to put this much vehemence into rebuking someone over a typo, it's generally a good idea to make sure that your own spelling and such is accurate. Otherwise you just look foolish. Now we're done.
Please Register or Log in to view the hidden image! My statement was clear as was your reply. You denied the actual transition at the Puysegur trench in favour of a mythic reversal. A typo that appears 4 times in a row, then in a different post is a bit more than a typo. Could be dyslexia if not misspelling. The point is that your attempt to teach me what is buoyancy and not spelling it correctly was quite amusing and striking. So I don't pretend to give lessons to others, especially in english spelling (you know that english is not my native language). Don't lie. You won't resist to post a reply.
