1 00:00:04,000 --> 00:00:07,040 This is Geology Bites with Oliver Strimpel. 2 00:00:08,600 --> 00:00:12,160 If you were to name the world's greatest mountain range, it 3 00:00:12,160 --> 00:00:17,160 would probably be the Himalaya. It has the world's highest peaks 4 00:00:17,400 --> 00:00:22,720 and stretches uninterruptedly for over 2500 kilometres from 5 00:00:22,720 --> 00:00:27,560 Afghanistan in the West to Burma and even Indonesia in the east. 6 00:00:28,600 --> 00:00:32,600 And it gives its name to the Alpine Himalayan Orogeny, the 7 00:00:32,600 --> 00:00:36,520 giant orogenic belt associated with the gradual closure of the 8 00:00:36,520 --> 00:00:41,800 Tethys Ocean that extends for over 15,000 kilometers from the 9 00:00:41,800 --> 00:00:46,320 Atlas Mountains and the Alps in the West to the Caucasus that 10 00:00:46,320 --> 00:00:50,320 border Europe and Asia to the Himalaya and even further E to 11 00:00:50,320 --> 00:00:54,520 Southeast Asia. But just north of the Himalaya, 12 00:00:54,520 --> 00:00:57,760 like several other great mountain ranges, we hear a lot 13 00:00:57,760 --> 00:01:03,560 less about the Karakoram, the Hindu Kush, the Pamir, the 14 00:01:03,560 --> 00:01:07,240 Gangdizi, the Kunlun Shan and the Tianshan. 15 00:01:08,400 --> 00:01:11,760 How can we explain the existence and geological makeup of these 16 00:01:11,760 --> 00:01:14,600 mountains? And are they part of the same 17 00:01:14,600 --> 00:01:17,400 geological circumstances that created the Himalaya? 18 00:01:19,360 --> 00:01:23,000 Mike Sahl has studied the Himalayan, Karakorum and Pamir 19 00:01:23,000 --> 00:01:27,200 mountain ranges for about 45 years, probably logging more 20 00:01:27,200 --> 00:01:29,800 hours in the field there than any other geologist. 21 00:01:30,480 --> 00:01:33,160 He has published hundreds of papers on the region and is 22 00:01:33,160 --> 00:01:36,080 perhaps best known for suggesting and documenting the 23 00:01:36,080 --> 00:01:40,600 evidence for a process called channel flow in the Himalaya, in 24 00:01:40,600 --> 00:01:45,360 which metamorphose crustal rocks are extruded towards the South, 25 00:01:45,880 --> 00:01:49,880 sandwiched between a thrust fault below and low angle normal 26 00:01:49,880 --> 00:01:53,400 faults above. He is emeritus professor of 27 00:01:53,400 --> 00:01:55,760 Wealth Sciences at the University of Oxford. 28 00:01:56,760 --> 00:01:59,880 Mike has been a keen advocate and advisor for the podcast 29 00:01:59,880 --> 00:02:04,080 since it's launch in 2020. He was my guest in the inaugural 30 00:02:04,080 --> 00:02:07,520 and the 50th episodes. Mike, I'm really happy to 31 00:02:07,520 --> 00:02:10,680 welcome you back to Geology Bites for this, the 100th 32 00:02:10,680 --> 00:02:12,680 episode. Well, thank you very much, 33 00:02:12,680 --> 00:02:14,600 Oliver. It's great to be back on Geology 34 00:02:14,600 --> 00:02:16,880 Bytes and thanks for inviting me again. 35 00:02:17,440 --> 00:02:20,480 Where exactly are these Central Asian mountains? 36 00:02:20,880 --> 00:02:24,440 And let me just point out for listeners that the supporting 37 00:02:24,440 --> 00:02:29,760 web page on geologybytes.com includes maps and the glossary, 38 00:02:29,840 --> 00:02:32,240 which might be especially useful for this episode. 39 00:02:32,720 --> 00:02:36,080 The geography of Central Asia is a little bit complicated, but as 40 00:02:36,080 --> 00:02:39,720 you said, the Himalayas are approximately 2 1/2 thousand 41 00:02:39,720 --> 00:02:42,680 kilometers long, running along the northern borders of 42 00:02:42,680 --> 00:02:46,240 Pakistan, India, Bhutan, Nepal and Tibet. 43 00:02:46,720 --> 00:02:50,240 And we're going to talk about the mountain ranges to the north 44 00:02:50,240 --> 00:02:53,960 of the Himalaya. So this group includes mountain 45 00:02:53,960 --> 00:02:58,480 ranges like the Pamir, which is almost entirely in Tajikistan, 46 00:02:59,240 --> 00:03:02,520 the Hindu Kush, which is the mountain range along the 47 00:03:02,600 --> 00:03:07,040 Pakistan Afghanistan border, the Karakorum, which is in 48 00:03:07,040 --> 00:03:09,240 northernmost Pakistan and Ladakh. 49 00:03:10,040 --> 00:03:12,880 And then there's a bunch of mountain ranges around Tibet. 50 00:03:12,880 --> 00:03:17,360 So the Gangesi range is about 2000 kilometres long, stretching 51 00:03:17,360 --> 00:03:20,520 from Kohistan in the West all the way along the southern 52 00:03:20,520 --> 00:03:23,440 margin of the Asian place in South Tibet. 53 00:03:24,360 --> 00:03:27,520 The Kunlun runs along the northern margin of the Tibetan 54 00:03:27,520 --> 00:03:31,880 Plateau in China, and the mountain ranges to the north of 55 00:03:31,880 --> 00:03:37,120 this are all in Outer Mongolia. So the Tianshan runs from the 56 00:03:37,120 --> 00:03:42,600 Pamirs in the southwest for about 3000 kilometres along the 57 00:03:42,880 --> 00:03:47,200 borders of Xinjiang province in China with Kazakhstan, 58 00:03:47,400 --> 00:03:51,720 Kyrgyzstan and Uzbekistan. By world standards, these are 59 00:03:51,720 --> 00:03:54,800 massive ranges. The Karakoram boasts 4 of the 60 00:03:54,800 --> 00:03:59,200 world's 8000 metre peaks, and the Hindu Kush, the Pamir, the 61 00:03:59,200 --> 00:04:03,160 Kunlunshan and the Tianshan each have many peaks above 7000 62 00:04:03,160 --> 00:04:06,080 meters. No mountain ranges outside this 63 00:04:06,080 --> 00:04:10,160 region have such high mountains. Yet we seldom hear much about 64 00:04:10,160 --> 00:04:12,840 these ranges. Do you think that is because 65 00:04:12,840 --> 00:04:14,560 they're overshadowed by the Himalaya? 66 00:04:15,160 --> 00:04:17,959 Well, quite possibly, yes. The Himalaya are actually 67 00:04:17,959 --> 00:04:22,600 readily accessible from the plains of India and Pakistan and 68 00:04:22,600 --> 00:04:26,040 are inhabited, so there are access roads, lots of villages 69 00:04:26,040 --> 00:04:28,560 up there and lots of trekking routes. 70 00:04:28,880 --> 00:04:32,480 So the access in the Karakoram is almost entirely by trekking 71 00:04:33,040 --> 00:04:35,640 or else mountain climbing at higher elevations. 72 00:04:36,240 --> 00:04:40,720 The Pamir, Tian Shan, and Kunlun are all extremely remote, but 73 00:04:40,720 --> 00:04:44,400 they're high, so they're on the plateau or around the plateau, 74 00:04:44,400 --> 00:04:47,440 and they do have Rd. access into their margins. 75 00:04:47,600 --> 00:04:51,560 Before we delve into the geology of some of these individual 76 00:04:51,560 --> 00:04:55,280 mountain ranges, can you give us a high level overview of the 77 00:04:55,280 --> 00:04:57,520 origin of these mountains? Yes. 78 00:04:57,680 --> 00:05:01,080 Overall, these mountain ranges are all part of the present day 79 00:05:01,080 --> 00:05:05,240 Eurasian plate, in contrast to the Himalayas which remember are 80 00:05:05,240 --> 00:05:08,760 all Indian plates. So the suture zone dividing the 81 00:05:08,760 --> 00:05:12,960 Himalayas from Southern Tibet, which runs right the way through 82 00:05:12,960 --> 00:05:16,600 Ladakh and S Tibet, that's the boundary between the collision 83 00:05:16,600 --> 00:05:19,440 zone between India and Central Asia. 84 00:05:20,400 --> 00:05:24,480 So these mountain ranges to the north of the Himalayas, in a 85 00:05:24,480 --> 00:05:29,280 nutshell, are all related to the progressive accretion or the 86 00:05:29,280 --> 00:05:33,520 collision of continental blocks onto the stable pre Cambrian 87 00:05:33,520 --> 00:05:37,120 shield areas of Siberia and Mongolia. 88 00:05:37,680 --> 00:05:41,520 So these continental terrains cause collisions dating way back 89 00:05:41,520 --> 00:05:46,400 into Paleozoic times. So that's more than 304 hundred 90 00:05:46,400 --> 00:05:49,920 million years ago. And the accretions of these 91 00:05:49,920 --> 00:05:53,120 terrains becomes younger as you go towards the South. 92 00:05:53,760 --> 00:05:58,880 So the oldest suture zones like the Mongol Altai suture zones in 93 00:05:58,880 --> 00:06:02,760 Mongolia are Paleozoic. The Kunlun is Triassic getting 94 00:06:02,880 --> 00:06:06,480 on for 300 to 250 million years ago. 95 00:06:07,320 --> 00:06:11,760 Central Tibet is a Jurassic Lower Cretaceous collision zone 96 00:06:11,760 --> 00:06:16,560 along the Bangong Suture. And the Indus Suture is the 97 00:06:16,560 --> 00:06:19,680 youngest of all of them, which is the one that caused the 98 00:06:19,680 --> 00:06:23,400 Himalayan collision. So this accretion of suture zans 99 00:06:23,400 --> 00:06:27,000 onto the main pre Cambrian blocks of Siberia and Mongolia 100 00:06:27,720 --> 00:06:31,280 could be the beginnings of formation of a giant crayon like 101 00:06:31,280 --> 00:06:35,000 we see in many of the old pre Cambrian belts, like the Cap Val 102 00:06:35,000 --> 00:06:38,680 Zimbabwe crayon in South Africa, where you have a bunch of 103 00:06:38,680 --> 00:06:43,320 Proterozoic terrains all accreted around the core of old 104 00:06:43,320 --> 00:06:46,160 Archaean rocks, some of the oldest rocks on the world. 105 00:06:47,400 --> 00:06:50,960 So the southern margin of Eurasia was this active plate 106 00:06:50,960 --> 00:06:55,120 margin right up through the Mesozoic as Tethys was forming 107 00:06:55,120 --> 00:06:59,920 to the South after the break up of Gondwana, you had active 108 00:06:59,920 --> 00:07:04,440 subduction underneath southern Tibet with this 2000 kilometre 109 00:07:04,440 --> 00:07:07,880 long granite baffa lifts of the Gangesi and that was all 110 00:07:07,880 --> 00:07:12,200 associated with this northward dipping subduction zone which 111 00:07:12,200 --> 00:07:16,320 consumed the oceanic lithosphere of Tethys to the South. 112 00:07:17,320 --> 00:07:20,520 So the Indian plate margin, the Himalayas was a long lasting 113 00:07:20,520 --> 00:07:24,680 passive continental margin with over 200 million years of stable 114 00:07:25,240 --> 00:07:28,880 shallow marine sedimentation. But the southern margin of Asia 115 00:07:28,880 --> 00:07:31,240 was an active Andean type margin. 116 00:07:31,600 --> 00:07:35,440 So it could actually have been relatively high and thick crust 117 00:07:35,600 --> 00:07:38,480 prior to the collision of India. Wow, that's fascinating. 118 00:07:38,640 --> 00:07:41,760 So I said in the introduction that you logged more hours in 119 00:07:41,760 --> 00:07:46,160 the area than any other gorges. Have you been to all these 120 00:07:46,160 --> 00:07:48,640 mountain ranges yourself and studied their geology? 121 00:07:49,280 --> 00:07:53,160 Well, yes, I have. I've worked for over 15 years 122 00:07:53,160 --> 00:07:57,360 along the Karakoram Ranges in North Pakistan, mostly in the 123 00:07:57,360 --> 00:08:01,440 Baltoro Glacier region. I published a big geological map 124 00:08:01,440 --> 00:08:05,080 of the central Karakoram in my book The Geology and Tectonics 125 00:08:05,080 --> 00:08:08,360 of the Karakoram Mountains. At least six of these 126 00:08:08,360 --> 00:08:12,400 expeditions to the high peaks were all on mountaineering 127 00:08:12,400 --> 00:08:14,680 expeditions. I soon figured out that the only 128 00:08:14,680 --> 00:08:17,120 way you could get up to this terrain was to have the 129 00:08:17,120 --> 00:08:21,040 logistics of a major Himalayan mountaineering expedition, and I 130 00:08:21,040 --> 00:08:25,120 usually invited 3 or 4 of my climbing mates along so that we 131 00:08:25,120 --> 00:08:29,240 could actually get high. So we had expeditions to K2, 132 00:08:29,240 --> 00:08:34,840 Mashibram, Trango Towers, Bialy and Hushay all during the late 133 00:08:34,840 --> 00:08:37,640 80s. And I've been to the Hindu Kush 134 00:08:37,679 --> 00:08:40,919 several times along the Pakistan Afghanistan border. 135 00:08:41,600 --> 00:08:44,560 It's always a bit dangerous crossing into Afghanistan. 136 00:08:44,560 --> 00:08:47,760 That's where the Panchaya Valley fighting was going on with the 137 00:08:47,760 --> 00:08:50,920 Mujahideen in those days. And I've also worked around 138 00:08:50,920 --> 00:08:55,120 Tibetan, the Tibetan Plateau for six or seven field seasons. 139 00:08:55,280 --> 00:08:59,120 We're going to talk in a moment about 3 of the ranges that you 140 00:08:59,120 --> 00:09:01,920 studied in a little bit more detail than the other ones. 141 00:09:02,400 --> 00:09:06,520 But first, I wonder if you could just briefly put into context 142 00:09:06,520 --> 00:09:10,280 the origin and the nature of the ranges that we will not be 143 00:09:10,280 --> 00:09:14,200 talking about in detail, which are the Tian Shan, the Kunlun 144 00:09:14,200 --> 00:09:17,640 Shan and the Gangdizi ranges. Yes, sure. 145 00:09:17,720 --> 00:09:20,920 Well, the Tian Shan and the Kunlun are older mountain 146 00:09:20,920 --> 00:09:23,720 ranges. They were formed during the 147 00:09:23,720 --> 00:09:26,680 middle or late Paleozoic. So we're looking at somewhere 148 00:09:26,680 --> 00:09:29,120 around 304 hundred million years ago. 149 00:09:29,840 --> 00:09:33,560 But their recent uplift has been attributed to the far field 150 00:09:33,560 --> 00:09:37,080 effects of the India Asia collision within the last 4030 151 00:09:37,080 --> 00:09:39,480 million years. Like all of the mountain ranges 152 00:09:39,480 --> 00:09:42,760 of Asia, the Gangesi range is different. 153 00:09:42,760 --> 00:09:47,920 This is a huge Andean type range that runs right the way across 154 00:09:47,920 --> 00:09:51,280 southern Tibet and it's almost entirely made-up of seduction 155 00:09:51,280 --> 00:09:56,160 related I type granite. So horn blend biotype bearing 156 00:09:56,160 --> 00:10:00,560 granites, granite diorites and andesitic volcanics as well, 157 00:10:00,560 --> 00:10:05,360 which span a long time, over 150 million years and these were 158 00:10:05,360 --> 00:10:08,560 formed above the northward dipping subduction zone that was 159 00:10:08,560 --> 00:10:12,720 consuming Teethis. So it was a geological setting 160 00:10:12,720 --> 00:10:14,800 very much like the Andes are today. 161 00:10:15,320 --> 00:10:19,240 Could you explain what I type granites are and andesitic 162 00:10:19,320 --> 00:10:23,360 volcanics? Yes, I type granites are ones 163 00:10:23,360 --> 00:10:26,680 that are derived from melting and igneous protolith. 164 00:10:27,320 --> 00:10:31,520 So they have a very distinct mineralogy and geochemistry from 165 00:10:31,840 --> 00:10:35,200 granites that are formed by continental crustal thickening 166 00:10:35,200 --> 00:10:38,840 like the Himalayas. The andocytic volcanics are very 167 00:10:38,840 --> 00:10:42,760 much like the volcanoes you see today in Washington state and 168 00:10:42,760 --> 00:10:44,560 Oregon. You know, Manson Helens is a 169 00:10:44,560 --> 00:10:49,280 classic andocytic volcanic and that is sitting above the Sierra 170 00:10:49,280 --> 00:10:52,400 Nevada baffilith, which is very similar geochemically to the 171 00:10:52,400 --> 00:10:56,600 Gangesi baffilith. So we can say with a fair degree 172 00:10:56,600 --> 00:11:01,240 of certainty what the geological setting of the Gangesi range 173 00:11:01,240 --> 00:11:03,920 was, and it would have been something very similar to what 174 00:11:03,920 --> 00:11:08,480 we see in the Andes or even the stretch from California up to 175 00:11:08,800 --> 00:11:12,480 British Columbia. OK, let's talk about the 176 00:11:12,480 --> 00:11:17,000 mountain ranges that you have studied in some detail, starting 177 00:11:17,000 --> 00:11:20,720 with the Karakorum. What are it's salient geological 178 00:11:20,720 --> 00:11:24,440 features and how do you compare these to the Himalaya? 179 00:11:25,320 --> 00:11:29,440 The Karakorum are relatively complicated compared to the 180 00:11:29,440 --> 00:11:32,960 Himalayas. The Karakorum have three major 181 00:11:32,960 --> 00:11:35,680 terrains. The northern Karakorum are 182 00:11:35,680 --> 00:11:39,480 composed dominantly of Paleozoic, early Mesozoic 183 00:11:39,480 --> 00:11:42,280 sedimentary rocks. So these are rocks that span 184 00:11:42,960 --> 00:11:48,560 from about 350 million years up to around 200 million years. 185 00:11:48,960 --> 00:11:53,120 They are intruded by some older diarritic plutons. 186 00:11:53,120 --> 00:11:56,240 For example, the most spectacular 1 you see on the 187 00:11:56,840 --> 00:12:00,160 West face of Gashebrum 4, this spectacular mountain that you 188 00:12:00,160 --> 00:12:02,360 see as you track up the Balsoro Glacier. 189 00:12:03,040 --> 00:12:06,400 The central Caracorum is all composed of this amazing 190 00:12:06,400 --> 00:12:08,440 backbone of the granite baphilith. 191 00:12:09,240 --> 00:12:12,160 And the southern Caracorum is all a high grade metamorphic 192 00:12:12,160 --> 00:12:15,720 terrain. These have classic Borovian 193 00:12:15,720 --> 00:12:18,240 fascies. Cyanite, Solomonite, nices, 194 00:12:18,720 --> 00:12:21,840 quinite, silimonite, and anderleucites are all aluminium 195 00:12:21,840 --> 00:12:26,240 silicates, and they're all the products of crustal thickening 196 00:12:26,600 --> 00:12:29,240 and regional metamorphism. Why is it? 197 00:12:29,240 --> 00:12:32,880 Called Borovian. That's named after George 198 00:12:32,880 --> 00:12:36,680 Barrow, who was one of the first geologists who traipsed over the 199 00:12:36,680 --> 00:12:40,520 Scottish Highlands and first came up with the Borovian 200 00:12:40,520 --> 00:12:44,760 sequence of metamorphism. This was over 120 years ago. 201 00:12:44,760 --> 00:12:49,000 At least he was the first person to really say there was this 202 00:12:49,240 --> 00:12:53,200 distinct mineralogy. As you increase pressure and 203 00:12:53,200 --> 00:12:57,120 temperature that you get a distinct sequence of rock. 204 00:12:57,120 --> 00:13:01,000 As you go from low pressure temperature green shish fascies, 205 00:13:01,000 --> 00:13:04,960 you'll get to higher pressure temperature amphibolite fascies. 206 00:13:04,960 --> 00:13:09,200 You go through a series of metamorphic isograds and Isograd 207 00:13:09,200 --> 00:13:13,800 is where the first incoming mineral formed and that terrain. 208 00:13:13,800 --> 00:13:17,680 So you go through from chloride to biotite to garnet, that's all 209 00:13:17,880 --> 00:13:22,040 greenish fascies. And then storilite, kainite, 210 00:13:22,040 --> 00:13:24,520 solomonite, which is the amphibolite fascies. 211 00:13:25,160 --> 00:13:27,240 And at the top of the amphibolite fascies, when you're 212 00:13:27,240 --> 00:13:32,600 getting up to temperatures in excess of about 700°C, you start 213 00:13:32,600 --> 00:13:36,600 melting the rock to produce a migmatite, and that's the first 214 00:13:36,720 --> 00:13:40,200 incoming melt that forms in that sequence when temperatures 215 00:13:40,200 --> 00:13:41,960 become high enough to melt the rock. 216 00:13:43,240 --> 00:13:46,640 In the Caricorum we have the most unique thing is this 217 00:13:46,640 --> 00:13:51,400 incredible central zone of the whole backbone of the Caricorum. 218 00:13:51,440 --> 00:13:55,920 This is enormous granite, Baphyllith, the Baltoro granite, 219 00:13:56,200 --> 00:14:00,200 which are composed of S type granites, granites derived from 220 00:14:00,200 --> 00:14:04,000 melting sedimentary rocks. They have a very distinct 221 00:14:04,000 --> 00:14:06,720 mineralogy, totally different from the Gangesi. 222 00:14:07,240 --> 00:14:11,280 The Baltoro Granites have garnet, tourmaline, muscovite 223 00:14:11,280 --> 00:14:16,040 and biotite and they form some of the most spectacular peaks 224 00:14:16,040 --> 00:14:20,160 along the Baltoro Glacier. I'm sure if anyone knows 225 00:14:20,160 --> 00:14:22,520 anything about the Caricorum, they've heard of the Trango 226 00:14:22,520 --> 00:14:26,600 Towers, which are these two three kilometre vertical walls 227 00:14:26,600 --> 00:14:28,200 of granite. Well, these are made of the 228 00:14:28,200 --> 00:14:33,760 Baltoro granite and they will have very high strontium 8786 229 00:14:33,760 --> 00:14:36,720 ratios, which is indicative of crustal melting. 230 00:14:37,640 --> 00:14:43,040 And the uranium lead zircon ages span around 21 to 13 million 231 00:14:43,040 --> 00:14:47,800 years, so that's early Miocene. Bizarrely, they happen to be 232 00:14:47,800 --> 00:14:50,920 exactly the same age as the Himalayan granites on the other 233 00:14:50,920 --> 00:14:53,920 plates of the South, the high Himalayan leucogranates. 234 00:14:54,520 --> 00:14:59,280 Can we then infer that they are in some sense the mirror image 235 00:14:59,320 --> 00:15:03,960 on the Eurasian plate of what was going on to the South on the 236 00:15:03,960 --> 00:15:05,600 Indian plate during the collision? 237 00:15:06,200 --> 00:15:09,400 Well, yes, temporarily speaking, they were mirror images. 238 00:15:09,400 --> 00:15:12,640 So it's sort of incredible that although the structure of the 239 00:15:12,640 --> 00:15:16,440 Caracorum and the Himalaya are very different following the 240 00:15:16,440 --> 00:15:20,840 collision, you've had the same 3040 million years of crustal 241 00:15:20,840 --> 00:15:25,080 thickening and regional metamorphism producing these 242 00:15:25,080 --> 00:15:28,720 Solomonite, quinite grade nices and migmatite. 243 00:15:29,400 --> 00:15:33,200 And you've also had the end products of that, which is the 244 00:15:33,200 --> 00:15:35,320 crustal melting to form the granite. 245 00:15:36,080 --> 00:15:40,400 But the big difference is that the Baltoro granites are 246 00:15:40,400 --> 00:15:44,480 absolutely enormous. And there's no doubt that it was 247 00:15:44,480 --> 00:15:49,280 a continuous baatholith, whereas the Himalayas were all these 248 00:15:49,280 --> 00:15:53,000 sort of individual pluton civil complexes produced from a 249 00:15:53,000 --> 00:15:56,840 regional magmatite. So the structure is very 250 00:15:56,840 --> 00:16:00,040 different. They're both pure crustal melts, 251 00:16:00,640 --> 00:16:03,880 but the Balturo requires an extra heat source to explain the 252 00:16:03,880 --> 00:16:07,280 massive volume of melt do. You think that heat must have 253 00:16:07,280 --> 00:16:10,400 come from the mantle? Yes, it almost certainly came 254 00:16:10,400 --> 00:16:13,760 from the mantle and we can get an idea of the involvement of 255 00:16:13,760 --> 00:16:18,600 the mantle from the very scarce lamprophyric dikes that intrude 256 00:16:18,600 --> 00:16:23,280 around the Balturo. So lamprifiers are these unusual 257 00:16:23,280 --> 00:16:26,760 mantle derived melts. They're basaltic type rocks. 258 00:16:27,640 --> 00:16:30,840 They have ages in the Karakoram that overlap exactly with the 259 00:16:30,840 --> 00:16:34,960 granite, so they're all early Miocene, suggesting that there 260 00:16:34,960 --> 00:16:39,240 was heat coming out of the upper mantle at the same time as the 261 00:16:39,240 --> 00:16:44,240 melting of the lower crust. Also in the Pamirs, which is the 262 00:16:44,240 --> 00:16:48,600 northern part of the Karakoram extending off to Tajikistan, 263 00:16:48,640 --> 00:16:53,480 there are spectacular series of ultra potassic volcanics and 264 00:16:53,480 --> 00:16:58,360 cyanide intrusions which are very similar geochemically and 265 00:16:58,520 --> 00:17:01,760 temporally to the lamprifiers that we have in the Boltura. 266 00:17:02,680 --> 00:17:06,200 And they all have ages around 11,000,000 years in the Pamiers. 267 00:17:07,000 --> 00:17:11,040 And these mantle derived intrusions are part of a huge 268 00:17:11,040 --> 00:17:15,200 range of similar rocks intruded through the plateau of Tibet. 269 00:17:15,400 --> 00:17:19,079 How do we know that the lamprophyric dikes and the ultra 270 00:17:19,079 --> 00:17:22,920 protasic cyanide intrusions originate from the mantle? 271 00:17:23,560 --> 00:17:25,440 Is it because of that chemical makeup? 272 00:17:26,200 --> 00:17:28,840 Yes, they're geochemically very distinct. 273 00:17:28,840 --> 00:17:33,000 They're highly alkaline, the silica under saturated so the 274 00:17:33,040 --> 00:17:36,040 opposite end of the scales are granite, and they're ultra 275 00:17:36,040 --> 00:17:40,680 potassic, so they're indicative of a highly enriched upper 276 00:17:40,680 --> 00:17:44,480 mantle source. Cyanides are like granites. 277 00:17:44,480 --> 00:17:48,640 There's coarse grained rocks with alkali feldspar. 278 00:17:49,440 --> 00:17:53,760 They form in thick continental crust by low degrees of partial 279 00:17:53,760 --> 00:17:57,560 melting, and they have to have a mantle component from the 280 00:17:57,640 --> 00:18:01,280 geochemistry. Do we have an idea why that 281 00:18:01,280 --> 00:18:04,600 extra heat from the matter was injected in the Caracorum and 282 00:18:05,080 --> 00:18:08,720 not elsewhere? Well, that's a very intriguing 283 00:18:08,720 --> 00:18:11,760 question and we don't really have an answer to it. 284 00:18:11,840 --> 00:18:15,320 I mean we know from the concentration of these highly 285 00:18:15,320 --> 00:18:20,320 alkaline lamprophyric rocks that they are an important components 286 00:18:20,320 --> 00:18:24,400 of many orogenic belts. They usually intruding at a very 287 00:18:24,400 --> 00:18:28,120 late stage, so whatever happens during the continental 288 00:18:28,120 --> 00:18:33,680 collision, the mantle has got an anomalous highly alkaline 289 00:18:34,240 --> 00:18:38,400 component to it right at the end of that origenic process. 290 00:18:39,120 --> 00:18:43,000 How do the Pamir relate to the Caricorum range which lies to 291 00:18:43,000 --> 00:18:45,520 their South? Well, the Pamir generally show 292 00:18:45,520 --> 00:18:49,680 older geology, more Paleozoic, lower Mesozoic rocks. 293 00:18:49,680 --> 00:18:53,920 There's nothing as young as we see in the Himalayas, but they 294 00:18:53,920 --> 00:18:58,360 also show very large scale post India Asia collision 295 00:18:58,800 --> 00:19:01,720 metamorphism. So similar to what we see in the 296 00:19:01,720 --> 00:19:04,800 southern Karakorum and in the Himalayas. 297 00:19:05,280 --> 00:19:08,600 Their pressure temperature conditions are very similar in 298 00:19:08,600 --> 00:19:12,920 all three mountain ranges and their uranium lead monocyte 299 00:19:12,920 --> 00:19:16,080 ages, which give you an indication of the timing of peak 300 00:19:16,080 --> 00:19:19,920 metamorphism are again very similar to the Karakorum and the 301 00:19:19,960 --> 00:19:24,040 Himalayas early Miocene. So they occur in a series of 302 00:19:24,120 --> 00:19:28,520 what we call these compressional core complexes along the 303 00:19:28,520 --> 00:19:33,280 Southern premier and they are directly related to the 304 00:19:33,280 --> 00:19:35,320 metamorphism in the southern Karakoram. 305 00:19:35,960 --> 00:19:39,240 Isn't it a bit surprising that the metamorphism in the Premier 306 00:19:39,640 --> 00:19:43,000 reflects similar pressure and temperature conditions to that 307 00:19:43,520 --> 00:19:46,080 of the Karakoram, even though the Premier, being further 308 00:19:46,080 --> 00:19:49,440 north, are much further from the collision zone with India? 309 00:19:49,920 --> 00:19:53,680 Well, it's not that surprising because the Southern Pamirs are 310 00:19:54,160 --> 00:19:57,160 geologically part of the same continental place as the 311 00:19:57,160 --> 00:19:59,760 Karakoram. There's a big suture that runs 312 00:19:59,760 --> 00:20:02,240 right through the central Pamirs. 313 00:20:02,240 --> 00:20:06,040 So the northern Pamirs are part of a different plate, but the 314 00:20:06,040 --> 00:20:09,640 Southern Pamirs and the Karakoram were contiguous with 315 00:20:09,640 --> 00:20:13,800 the same plate. OK, let's talk about the Hindu 316 00:20:13,800 --> 00:20:16,280 Kush. Well, the Hindu Kush is really 317 00:20:16,280 --> 00:20:20,760 the western extension of the Karakoram, runs right from 318 00:20:20,760 --> 00:20:24,200 northern Pakistan. Then it swings S along the 319 00:20:24,200 --> 00:20:27,880 Afghan border. And although it's a similar 320 00:20:27,880 --> 00:20:30,320 geological plate to the Karakoram, it has a very 321 00:20:30,320 --> 00:20:33,480 different geology. Most of the rocks in the Hindu 322 00:20:33,480 --> 00:20:36,920 Kush are again older sedimentary rocks. 323 00:20:36,920 --> 00:20:40,800 So Paleozoic, early Mesozoic sedimentary rocks. 324 00:20:41,520 --> 00:20:44,720 They have very few collision related granites. 325 00:20:44,720 --> 00:20:48,200 So whereas the Karakoram has enormous volumes of Baltoro 326 00:20:48,200 --> 00:20:53,120 granite, there's only really one intrusion near Chitral in 327 00:20:53,120 --> 00:20:58,000 northwest Pakistan, which is a Miocene post collisional 328 00:20:58,000 --> 00:21:01,240 granite. The rest of the granitic rocks 329 00:21:01,240 --> 00:21:05,800 up there are older and deformed and metamorphosed amphibolite 330 00:21:05,800 --> 00:21:09,880 rocks which started life off as I type granite. 331 00:21:09,880 --> 00:21:13,000 It's very similar to the Gangesi, but they've undergone a 332 00:21:13,000 --> 00:21:16,640 huge metamorphism and defamation after intrusion. 333 00:21:17,480 --> 00:21:20,880 The Hindu Kush also interestingly, has the world's 334 00:21:20,880 --> 00:21:23,560 deepest known continental seismic zone. 335 00:21:23,560 --> 00:21:27,200 So despite having this old geology and not a lot of 336 00:21:27,200 --> 00:21:31,640 indications of crustal melting post collision, it has this 337 00:21:31,640 --> 00:21:36,080 continental seismic zone in which earthquakes extend down to 338 00:21:36,080 --> 00:21:41,480 about 250, even 300 kilometres. And these earthquakes define a 339 00:21:41,480 --> 00:21:45,040 very narrow zone. It is the deepest continental 340 00:21:45,040 --> 00:21:47,400 seismic zone we know on the planet. 341 00:21:48,280 --> 00:21:51,560 There's a second seismic zone to the north called the Pannier 342 00:21:51,560 --> 00:21:55,280 seismic zone, which defines a shallower S dipping zone. 343 00:21:55,720 --> 00:21:59,640 So you have two converging continental subduction zones, 344 00:21:59,640 --> 00:22:03,160 the deep Hindu Kush and the shallower Pamir. 345 00:22:03,680 --> 00:22:06,080 And it's probably the convergence of those two 346 00:22:06,080 --> 00:22:09,680 subduction zones that lifts up the whole of the Pamir Plateau. 347 00:22:10,120 --> 00:22:13,520 Wow, that's very interesting. Continental subduction is fairly 348 00:22:13,600 --> 00:22:16,000 rare, and here you have two of them going on in opposite 349 00:22:16,000 --> 00:22:19,360 polarities right in the same part of the world. 350 00:22:19,840 --> 00:22:24,000 How can continental crust subduct to these enormous 351 00:22:24,000 --> 00:22:27,240 depths, given that it's a lot lighter than what it's 352 00:22:27,240 --> 00:22:30,440 subducting into? Yes, well, good question. 353 00:22:30,960 --> 00:22:34,120 Most deep seismic zones are in the oceans. 354 00:22:34,280 --> 00:22:37,360 Of course, in the oceans all around the Pacific Ring of Fire, 355 00:22:37,360 --> 00:22:41,480 you have very deep oceanic subduction zones, which is the 356 00:22:41,480 --> 00:22:43,760 subduction of oceanic lithosphere. 357 00:22:44,440 --> 00:22:47,480 But in the continents, it's very uncommon to get these deep 358 00:22:47,480 --> 00:22:49,960 earthquakes. So along the Himalayas and S 359 00:22:49,960 --> 00:22:54,240 Tibet, the deepest earthquakes occur around 70, maybe 80 360 00:22:54,240 --> 00:22:57,760 kilometres depth. So there's several factors you 361 00:22:57,760 --> 00:23:00,480 need to make this deep seismic zone. 362 00:23:00,480 --> 00:23:05,080 You need rapid subduction. You need old cold material being 363 00:23:05,080 --> 00:23:09,360 subducted and you need to keep the temperatures low enough to 364 00:23:09,360 --> 00:23:12,120 make the earthquakes. Earthquakes only occur at 365 00:23:12,120 --> 00:23:17,040 temperatures less than five 5600°C. 366 00:23:17,480 --> 00:23:22,200 So how on earth can you get low temperatures 250 kilometres deep 367 00:23:22,200 --> 00:23:25,400 in the mantle? The answer is the only way you 368 00:23:25,400 --> 00:23:29,080 can do it is by this very narrow subduction of old cold 369 00:23:29,080 --> 00:23:32,680 continental crust and that is most likely going to be lower 370 00:23:32,680 --> 00:23:34,960 Indian crust subducting northwards. 371 00:23:36,200 --> 00:23:40,080 So we know in the geological record there's over 15 or 16 372 00:23:40,600 --> 00:23:43,600 ultra high pressure terrains. They're all from the Cambrian 373 00:23:43,880 --> 00:23:47,160 onwards and they occur on all the continent. 374 00:23:47,880 --> 00:23:52,200 So we do know that it's possible to subduct continental crustal 375 00:23:52,200 --> 00:23:54,880 rocks to these depth. And the rocks you've formed down 376 00:23:54,880 --> 00:23:58,400 there are first kozite bearing, which is a high pressure 377 00:23:58,880 --> 00:24:02,600 polymorphic quartz kozite eclogites and the other are 378 00:24:02,600 --> 00:24:05,240 micro diamonds. So diamond difference exclagites 379 00:24:05,240 --> 00:24:08,560 we see in places like the Western Nice region in Norway. 380 00:24:09,200 --> 00:24:13,880 And we know they occur in subducted continental rocks and 381 00:24:13,880 --> 00:24:18,440 that is exactly what's happening under the Hindu Kush today. 382 00:24:18,880 --> 00:24:21,720 The other thing you need to do, apart from getting them down 383 00:24:21,720 --> 00:24:25,600 there very quickly, is to exhume them very rapidly to get them 384 00:24:25,600 --> 00:24:29,080 back to the surface. So you do need some sort of slab 385 00:24:29,080 --> 00:24:31,640 break off. You need to release the anchor 386 00:24:31,720 --> 00:24:35,280 that has dragged them down to mantle depths so the buoyancy 387 00:24:35,280 --> 00:24:38,400 forces take over and these rocks will pop straight up to the 388 00:24:38,400 --> 00:24:41,800 surface. If these ultra deep earthquakes 389 00:24:41,800 --> 00:24:45,960 in the Hindukur stem from the subduction of low Indian crust, 390 00:24:46,200 --> 00:24:50,120 wouldn't we also expect to see such Jeep earthquakes further E 391 00:24:50,120 --> 00:24:54,000 under the Karakoram or Tibet? Well, that is a very good point. 392 00:24:54,080 --> 00:24:57,600 And the answer is we don't see that people have speculated on 393 00:24:57,600 --> 00:25:00,600 this for a while. So in the central part of the 394 00:25:00,600 --> 00:25:03,720 Himalayan, the Tibet, we don't see this deep structure. 395 00:25:04,280 --> 00:25:08,280 What we do see is the lower Indian crust, which is all the 396 00:25:08,280 --> 00:25:12,800 Archaean Indian shield under placing the Himalayas, under 397 00:25:12,800 --> 00:25:16,720 placing the Tibetan plateau. And this was a mechanism that 398 00:25:16,720 --> 00:25:21,040 Emil Argan, the great Swiss geologist, suggested over 100 399 00:25:21,040 --> 00:25:24,200 years ago, that rather than the deep subduction zone, you have a 400 00:25:24,200 --> 00:25:28,720 much shallower under placing of lower Indian crust underneath 401 00:25:28,720 --> 00:25:31,400 southern Tibet. So there's a kind of bifurcation 402 00:25:31,400 --> 00:25:35,760 really between the mode of subduction you have under the 403 00:25:35,760 --> 00:25:40,040 Hindu Kush on the western end, which goes very deep, and the 404 00:25:40,040 --> 00:25:45,240 shallow under plating of the Indian plate further E which 405 00:25:45,240 --> 00:25:49,640 just slides underneath. Do we have any idea as to why we 406 00:25:49,640 --> 00:25:53,160 get these two different modes and what causes the Indian plate 407 00:25:53,160 --> 00:25:56,120 to do one at one end and the other at the other? 408 00:25:57,040 --> 00:26:00,200 Well, there's something very special about the two syntaxes, 409 00:26:00,200 --> 00:26:04,280 which is the northwest corner and the North East corner, where 410 00:26:04,280 --> 00:26:07,760 the Himalayas go from east West to north-south. 411 00:26:08,400 --> 00:26:13,480 All of the structures swing around through 90°, down through 412 00:26:13,480 --> 00:26:17,040 the Chaman ranges of the Pakistan Afghanistan border on 413 00:26:17,040 --> 00:26:20,760 the West and down through the Indo Berman ranges on the east. 414 00:26:21,680 --> 00:26:28,240 And at both of those syntaxes there are 78000 meter mountains 415 00:26:28,240 --> 00:26:32,120 which have the youngest metamorphism known anywhere on 416 00:26:32,120 --> 00:26:35,360 the planet. So the Nangoparbat metamorphism. 417 00:26:35,960 --> 00:26:41,240 Nangoparbat is this 8000 meter peak in the northwestern part of 418 00:26:41,240 --> 00:26:45,840 Pakistan is actually the western end of the Himalayas rather than 419 00:26:45,840 --> 00:26:50,520 being in the Karakoram. And the northeast is a mountain 420 00:26:50,520 --> 00:26:54,400 called Namchi Bawa, which also has extremely young 421 00:26:54,400 --> 00:26:57,360 metamorphism. In both of these areas, the 422 00:26:57,360 --> 00:27:03,240 rocks were formed less than one to two million years ago and 423 00:27:03,240 --> 00:27:07,640 were exhumed extremely rapidly. So you have this enormous 424 00:27:08,000 --> 00:27:11,280 exhumation of deep crustal metamorphic rocks in a very 425 00:27:11,280 --> 00:27:14,480 shallow time. And the reason we think is 426 00:27:14,480 --> 00:27:18,400 structural that the rocks in the main part of the Himalayas are 427 00:27:18,400 --> 00:27:20,840 extruding to the South channel flow. 428 00:27:21,640 --> 00:27:26,640 But in the Syntaxes region, they are having compressive stresses 429 00:27:26,640 --> 00:27:29,320 of everywhere. So there is nowhere else to go 430 00:27:29,320 --> 00:27:33,960 but straight upwards and that's exactly what we see so. 431 00:27:34,360 --> 00:27:38,280 Although India collided with Asia about 50 million years ago, 432 00:27:38,600 --> 00:27:43,080 it continues its northward advance to this day, albeit at 433 00:27:43,080 --> 00:27:45,320 about half the pre collision speed. 434 00:27:46,200 --> 00:27:50,640 How is this movement accommodated and is that part of 435 00:27:50,640 --> 00:27:53,720 the story of the ongoing uplift of the mountain ranges we've 436 00:27:53,720 --> 00:27:57,160 been discussing? Well, yes, there's two theories 437 00:27:57,160 --> 00:28:00,720 of how the northward push of India was and is continuing to 438 00:28:00,720 --> 00:28:04,120 be absorbed in Asia. Firstly, there was the one that 439 00:28:04,120 --> 00:28:09,280 was first proposed by Emil Argand in 1924 where he 440 00:28:09,280 --> 00:28:12,240 suggested that India was under thrusting the whole of the 441 00:28:12,240 --> 00:28:14,360 Tibetan plateau and jacking it up. 442 00:28:15,640 --> 00:28:19,280 The second model is that of continental extrusion and this 443 00:28:19,280 --> 00:28:23,040 was first proposed by Peter Molnar and Paul Tapini back in 444 00:28:23,040 --> 00:28:26,480 the 1980s. This was based on when Landsat 445 00:28:26,480 --> 00:28:30,760 photography first became available and when you laid out 446 00:28:30,760 --> 00:28:34,240 all these Landsat photos of Tibet and Central Asia, the 447 00:28:34,240 --> 00:28:37,400 thing that really strikes you immediately are these huge 448 00:28:37,400 --> 00:28:40,520 strike slip faults, San Andreas type faults, but they're going 449 00:28:40,520 --> 00:28:43,200 on for thousands of kilometres across Central Asia. 450 00:28:44,200 --> 00:28:48,200 So Moulnar and Tapani proposed that the thickened crust of 451 00:28:48,200 --> 00:28:53,280 Tibet was being squeezed out to the east to make way for India 452 00:28:53,280 --> 00:28:57,640 pushing towards the north. They wanted, at the time, over 453 00:28:57,640 --> 00:29:00,800 1000 kilometers of offsets on these bounding strike slip 454 00:29:00,800 --> 00:29:04,880 fault. So what observations can help us 455 00:29:04,880 --> 00:29:06,760 distinguish between these two models? 456 00:29:07,040 --> 00:29:10,360 Well, the continental extrusion model is very easily testable 457 00:29:10,360 --> 00:29:15,640 because these strike slip faults are exposed to the surface and 458 00:29:15,800 --> 00:29:20,120 all you need is a pinning points of a well dated granite or 459 00:29:20,360 --> 00:29:24,000 sedimentary rock or anything that you know was once 460 00:29:24,120 --> 00:29:28,280 continuous and is now being offset by X amount of slip. 461 00:29:29,040 --> 00:29:32,880 And when this extrusion model was first proposed, there were 462 00:29:32,880 --> 00:29:35,880 no geological maps. There was no constraints on the 463 00:29:35,880 --> 00:29:37,880 amount of slip of any of these faults. 464 00:29:38,720 --> 00:29:43,640 So we went into the Karakoran Fault back in the 1980s and 465 00:29:43,640 --> 00:29:47,240 carried out very detailed work along the Karakoran Fault in 466 00:29:47,240 --> 00:29:50,880 Ladakh, where it's beautifully exposed and a whole series of 467 00:29:50,880 --> 00:29:53,360 granites. And by getting very accurate 468 00:29:53,360 --> 00:29:57,480 uranium lead zircon ages on each one of these granite, we were 469 00:29:57,480 --> 00:30:01,920 able to map the dextral offsets. And we found that the offsets of 470 00:30:01,920 --> 00:30:06,680 these myosin granites was no more than 120 kilometers on the 471 00:30:06,680 --> 00:30:09,960 Karakoran Fault, one of the most active strikes at faults of 472 00:30:09,960 --> 00:30:13,600 Tibet, which happens to be exactly the same as the course 473 00:30:13,600 --> 00:30:17,440 of the ancient Indus River, which was captured by the fault, 474 00:30:17,440 --> 00:30:21,200 dragged for 120 kilometres before it cuts S back into 475 00:30:21,200 --> 00:30:24,120 northern Ladakh. Well, that would seem to be 476 00:30:24,200 --> 00:30:28,360 pretty conclusive evidence. Do the proponents of the 477 00:30:28,560 --> 00:30:31,160 extrusion tectonics accept these arguments? 478 00:30:31,640 --> 00:30:33,600 Do you have to? Basically because it's good 479 00:30:33,600 --> 00:30:37,480 proper science. But the problem was on the other 480 00:30:37,480 --> 00:30:38,960 faults. We couldn't learn in the Alton 481 00:30:38,960 --> 00:30:41,840 tag and nothing like as clear cut as the Karakorum. 482 00:30:41,840 --> 00:30:45,600 So there were no definitive pinning points and you're 483 00:30:45,600 --> 00:30:50,600 reliant more there on the extensive the ductile slip along 484 00:30:50,600 --> 00:30:54,440 those faults. So the take home message of all 485 00:30:54,440 --> 00:30:58,880 of this is that continental extrusion was working as a 486 00:30:58,880 --> 00:31:04,160 process, but it was nowhere near the amount that Peter Molnar and 487 00:31:04,160 --> 00:31:06,680 Paul Taponiere originally proposed. 488 00:31:06,680 --> 00:31:08,960 It was more like each one of these faults had somewhere 489 00:31:08,960 --> 00:31:13,560 between 150 and maybe 3 or 400 kilometres maximum. 490 00:31:14,000 --> 00:31:17,880 So if we have this lower amount of extrusion going on, the 491 00:31:17,880 --> 00:31:21,400 remainder of the accommodation of the northern part of the 492 00:31:21,400 --> 00:31:25,480 Indian plate moving up is accommodated by this flat slab 493 00:31:25,480 --> 00:31:29,960 subduction and uplift and folding throughout the crust to 494 00:31:29,960 --> 00:31:33,080 the north. Yes, and all the Himalayas 495 00:31:33,120 --> 00:31:36,600 indicate hundreds of kilometers of homogeneous crustal 496 00:31:36,600 --> 00:31:39,400 shortening. That's folding, thrusting. 497 00:31:39,400 --> 00:31:42,360 That shortens the crust and thickens the crust and then you 498 00:31:42,360 --> 00:31:45,440 get the metamorphism. But all of the rocks in the 499 00:31:45,440 --> 00:31:48,440 Himalayas are Proterozoic or younger. 500 00:31:48,640 --> 00:31:53,560 There's nothing older than about 1000 million years. 501 00:31:54,120 --> 00:31:58,800 So we know that the lower crust of India, which is dominantly 502 00:31:58,800 --> 00:32:02,360 the pre Cambrian Indian shield, these are Archaean rocks, which 503 00:32:02,360 --> 00:32:06,280 are much, much older. They're very old, high grade 504 00:32:06,280 --> 00:32:08,960 granulite fascies rocks. So they're dry and they're 505 00:32:08,960 --> 00:32:13,560 competent, and it's the shallow subduction of the lower part of 506 00:32:13,560 --> 00:32:17,040 the Indian plate that is jacking up the Himalayas, and it's 507 00:32:17,040 --> 00:32:20,960 jacking up southern Tibet, if not most of Tibet itself. 508 00:32:21,480 --> 00:32:24,360 And that act of fault is the one that all the big earthquakes 509 00:32:24,360 --> 00:32:26,040 along the Himalayas occurred today. 510 00:32:26,040 --> 00:32:29,960 So the main Himalayan fault is where, for example, the Gawker 511 00:32:29,960 --> 00:32:34,560 earthquake 2015 set off from the Great Assam earthquake. 512 00:32:34,640 --> 00:32:38,640 All of those are on the southern boundary of the Himalayas, which 513 00:32:38,640 --> 00:32:42,320 is where the Indian shield is subducting beneath the Himalayas 514 00:32:42,640 --> 00:32:46,440 and jacking it up. Do other mountain ranges, such 515 00:32:46,440 --> 00:32:51,720 as the Alps or the Andes, have the kinds of satellite mountain 516 00:32:51,720 --> 00:32:54,360 ranges that we've been talking about today with respect to the 517 00:32:54,360 --> 00:32:58,000 Himalaya? Well, all mountain ranges are 518 00:32:58,000 --> 00:33:00,360 different. The Alps is part of the Tethian 519 00:33:00,360 --> 00:33:02,720 collision zone. It's the same as the Himalayas 520 00:33:02,720 --> 00:33:07,360 temporarily, but it shows totally different structures. 521 00:33:07,760 --> 00:33:11,200 The Alps have much more high pressure, ultra high pressure 522 00:33:11,200 --> 00:33:12,960 rocks than we see in the Himalayas. 523 00:33:13,640 --> 00:33:16,640 There's very little regional metamorphism in the Alps, 524 00:33:16,640 --> 00:33:18,800 whereas in the Himalayas it's huge. 525 00:33:18,800 --> 00:33:23,800 Most of the greater Himalayan sequences all that the Alps have 526 00:33:23,880 --> 00:33:29,280 almost no crustal melt granites associated with the young 527 00:33:29,280 --> 00:33:31,800 collision zones. So there's nothing like channel 528 00:33:31,800 --> 00:33:34,400 flow. The Andes are completely 529 00:33:34,400 --> 00:33:37,400 different from the Himalayas. The Andes show a geology very 530 00:33:37,400 --> 00:33:40,920 similar to the Gangesi. You know I type granites related 531 00:33:40,920 --> 00:33:43,560 to subduction of oceanic lithosphere beneath the 532 00:33:43,560 --> 00:33:46,400 continent. Big explosive andesitic 533 00:33:46,400 --> 00:33:50,720 volcanics like Manson, Helens and porphyry copper deposits 534 00:33:50,720 --> 00:33:53,680 typically. So yeah, all mountain ranges are 535 00:33:53,680 --> 00:33:57,200 different, which makes geology all the more interesting. 536 00:33:58,200 --> 00:34:00,120 Mike Sowell, thank you very much. 537 00:34:00,680 --> 00:34:02,480 Thank you, Oliver. It's been a pleasure. 538 00:34:03,800 --> 00:34:06,480 To see pictures and illustrations that support this 539 00:34:06,480 --> 00:34:12,080 podcast, go to geologybytes.com, where you'll also find 540 00:34:12,080 --> 00:34:15,520 transcripts and a subject matter index of all the episodes. 541 00:34:16,080 --> 00:34:19,440 There you can also give me feedback which I welcome, as 542 00:34:19,440 --> 00:34:22,440 well as sign up to get my emails about new episodes.