1 00:00:05,000 --> 00:00:08,800 This is Java g. B, with all of us trampled to 2 00:00:08,800 --> 00:00:11,500 address many important geological questions. 3 00:00:11,600 --> 00:00:14,800 We often need to determine the history of a crystalline Rock. 4 00:00:15,500 --> 00:00:19,200 When it initially, formed out of a melt and what temperature and 5 00:00:19,200 --> 00:00:21,900 pressures, it may have been subjected to between its 6 00:00:21,900 --> 00:00:26,600 formation and the present day. One important way of doing this 7 00:00:26,600 --> 00:00:30,000 is to look within the rock to see if it contains minerals that 8 00:00:30,000 --> 00:00:31,900 are especially useful for this purpose. 9 00:00:33,200 --> 00:00:36,000 In previous episodes. We've talked about Zircon 10 00:00:36,000 --> 00:00:39,400 crystals and how we can use the decay of uranium to lead to 11 00:00:39,400 --> 00:00:41,600 obtain their crystallization ages. 12 00:00:42,500 --> 00:00:46,900 But in addition to their value as Gio chronometers zircons and 13 00:00:46,900 --> 00:00:51,400 other crystals such as those of monazite Titanite and rutile 14 00:00:51,800 --> 00:00:54,400 contain a number of elements in Trace Amounts. 15 00:00:55,400 --> 00:00:58,100 This makes them valuable as targets for geochemical 16 00:00:58,100 --> 00:01:01,800 analysis, as well. By measuring these Trace 17 00:01:01,800 --> 00:01:05,099 abundances, we can learn quite a bit about the environment in 18 00:01:05,099 --> 00:01:09,300 which the crystal formed this contributes to our understanding 19 00:01:09,300 --> 00:01:12,300 of the Rocks history. Both as to the origin of the 20 00:01:12,300 --> 00:01:15,600 Melt art, of which the crystals formed, as well as the 21 00:01:15,600 --> 00:01:18,300 temperatures and pressures that prevailed when the crystal was 22 00:01:18,300 --> 00:01:23,100 forming, Two challenges have long, been devil, geochronology 23 00:01:23,100 --> 00:01:26,800 and geochemistry, the first is the sheer amount of labor 24 00:01:26,800 --> 00:01:30,200 involved in obtaining a corpus of trustworthy, radiometric, 25 00:01:30,200 --> 00:01:33,500 dates or accurate Trace, element abundances. 26 00:01:34,300 --> 00:01:37,900 The second is the difficulty of ensuring that the geochronology 27 00:01:38,100 --> 00:01:41,900 and the geochemistry analyses actually, apply to the same part 28 00:01:41,900 --> 00:01:46,200 of a crystal and are not biased by variations within a crystal. 29 00:01:46,900 --> 00:01:49,800 This can be especially difficult when a crystal contains pains 30 00:01:49,800 --> 00:01:53,300 several tiny, domains each reflecting a different phase for 31 00:01:53,300 --> 00:01:57,900 the crystals history. John quartal and his team have 32 00:01:57,900 --> 00:02:00,300 developed a technique that has largely overcome. 33 00:02:00,300 --> 00:02:04,300 These hurdles, this has led to a revolution in our ability to 34 00:02:04,300 --> 00:02:07,700 unravel metamorphic histories and has given rise to a new 35 00:02:07,700 --> 00:02:10,000 field called petrol. Chronology. 36 00:02:11,000 --> 00:02:14,200 John Carter is a professor in the department of earth science 37 00:02:14,200 --> 00:02:18,200 at the University of California. Santa Barbara Giancarlo. 38 00:02:18,200 --> 00:02:20,700 Welcome to geology B. Thank you Oliver. 39 00:02:20,700 --> 00:02:23,200 It's a real pleasure to be here and to talk with you about this 40 00:02:23,200 --> 00:02:26,400 really exciting topic. I said in my introduction, That 41 00:02:26,400 --> 00:02:29,700 one of the challenges faced by geochronology and geochemistry 42 00:02:29,700 --> 00:02:32,700 is the sheer amount of work involved in getting to a result. 43 00:02:33,500 --> 00:02:36,500 I have first-hand experience of dating, Luca granite's from the 44 00:02:36,500 --> 00:02:41,300 Himalaya, this way the method I use called thermal ionization 45 00:02:41,300 --> 00:02:43,900 Mass spectrometry was certainly laborious. 46 00:02:44,400 --> 00:02:47,900 I started by Smashing up the rock samples, separating out the 47 00:02:47,900 --> 00:02:52,400 Reza Khan Sometimes, using highly toxic heavy liquids and 48 00:02:52,400 --> 00:02:55,000 reeling them in a furnace, dissolving them in hydrofluoric 49 00:02:55,000 --> 00:02:57,200 acid. And then mounting, the dissolved 50 00:02:57,200 --> 00:03:01,000 material is a gel onto a filament to be inserted as the 51 00:03:01,000 --> 00:03:02,900 cathode inside, a mass spectrometer. 52 00:03:03,800 --> 00:03:06,300 All the, while I had to pay obsessive attention to 53 00:03:06,300 --> 00:03:10,500 cleanliness as at the end of the day, when is just measuring mere 54 00:03:10,500 --> 00:03:14,800 picograms of that. Led Decay products of uranium, I 55 00:03:14,800 --> 00:03:18,300 presume obtaining accurate abundances of Trace elements. 56 00:03:18,300 --> 00:03:22,200 Within the crystal can also be very labor-intensive, that's 57 00:03:22,200 --> 00:03:24,100 right. It's a very similar process to 58 00:03:24,100 --> 00:03:26,700 obtain Trace elements in. Is minerals. 59 00:03:26,700 --> 00:03:30,800 You need to take the mineral and dissolve it, and then separate 60 00:03:30,800 --> 00:03:33,500 out the individual elements using complex column chemistry, 61 00:03:34,200 --> 00:03:36,700 or you need to use some Institute technique that you 62 00:03:36,700 --> 00:03:40,400 might be able to avoid some of those complicated processes and 63 00:03:40,400 --> 00:03:43,300 really get directly at individual parts of the crystal. 64 00:03:43,800 --> 00:03:47,600 So can you tell us how the fields is Advanced since then? 65 00:03:48,500 --> 00:03:51,100 Yeah. So initially we would take parts 66 00:03:51,100 --> 00:03:54,900 or whole crystals and dissolve them up and separate out the 67 00:03:54,900 --> 00:03:57,700 elements of Interest. And really we've moved on then 68 00:03:57,700 --> 00:04:01,300 to try and make in-situ measurements of parts of 69 00:04:01,300 --> 00:04:03,500 crystals down to the Micron scale. 70 00:04:03,500 --> 00:04:07,000 And it really started with electron probe micro analyzers 71 00:04:07,000 --> 00:04:09,600 which are relatively old technology, but useful for 72 00:04:09,600 --> 00:04:12,600 measuring Trace element concentrations down to about 100 73 00:04:12,600 --> 00:04:16,100 or so parts per million subsequent to that a couple of 74 00:04:16,100 --> 00:04:18,899 other techniques were developed primarily laser ablation 75 00:04:18,899 --> 00:04:21,300 inductively, coupled, plasma mass spectrometry. 76 00:04:21,500 --> 00:04:24,000 And also secondary. Ionization Mass spectrometry 77 00:04:24,000 --> 00:04:27,500 were both used. The advantages of those are that 78 00:04:27,500 --> 00:04:30,200 they can measure Trace elements down to the parts per million 79 00:04:30,200 --> 00:04:33,900 and in some cases even down to parts per billion concentrations 80 00:04:33,900 --> 00:04:36,900 of Trace elements. Okay, let's concentrate on the 81 00:04:36,900 --> 00:04:39,600 laser ablation techniques since that's the one that you've 82 00:04:39,600 --> 00:04:44,100 refined what is the role of the laser ablation system? 83 00:04:44,700 --> 00:04:48,000 A laser ablation system, really is just a way of sampling, the 84 00:04:48,000 --> 00:04:51,400 material, it just takes the mineral itself and disaggregate 85 00:04:51,400 --> 00:04:55,100 it into relatively small or relatively fine particles and 86 00:04:55,100 --> 00:04:57,300 then we take them. Fine particles and we transport 87 00:04:57,300 --> 00:04:59,900 them to the Argon plasma. So you can think of the laser 88 00:04:59,900 --> 00:05:03,300 ablation system as a way of sampling or drilling out 89 00:05:03,500 --> 00:05:07,200 material and disaggregating enter very small Crystal sport 90 00:05:07,200 --> 00:05:10,900 parts of crystals to then separate those using the plasma 91 00:05:10,900 --> 00:05:14,600 Source itself which is an inductively coupled plasma, and 92 00:05:14,600 --> 00:05:17,800 what is its role here. So inductively, coupled plasma 93 00:05:17,800 --> 00:05:21,100 is, if you take an Argon gas, and you heat that Argon gas to 94 00:05:21,100 --> 00:05:25,200 around 11,000 K using an electrical source. 95 00:05:25,600 --> 00:05:28,200 You can ionize that argon and turn it into a plasma. 96 00:05:28,700 --> 00:05:32,700 If you take then solid pieces or liquid material, you can pass 97 00:05:32,700 --> 00:05:35,100 that into that plasma and you can essentially take that 98 00:05:35,100 --> 00:05:37,900 material and ionize it in that argon plasma. 99 00:05:38,400 --> 00:05:42,000 And then you can produce ions of individual elements and then you 100 00:05:42,000 --> 00:05:45,100 can use a mass spectrometer to separate those individual ions 101 00:05:45,100 --> 00:05:47,200 and measure their relative abundances. 102 00:05:47,700 --> 00:05:50,500 Okay. I see, so the inductive coupling 103 00:05:50,500 --> 00:05:54,200 of the Argon is the way you heat up the Argon gas to the 104 00:05:54,200 --> 00:05:58,500 extremely high temperatures. Eleven thousand Kelvin, when all 105 00:05:58,500 --> 00:06:01,000 the electrons are stripped off and it becomes a plasma. 106 00:06:01,200 --> 00:06:03,400 That's right. So, you take your solid pieces 107 00:06:03,400 --> 00:06:07,200 of zircon or monocyte, and you have those as very small 108 00:06:07,300 --> 00:06:10,100 particle size and you take those particles and you pass them into 109 00:06:10,100 --> 00:06:12,100 a plasma. And essentially you strip 110 00:06:12,100 --> 00:06:15,700 electrons from those particles and eventually you strip enough 111 00:06:15,700 --> 00:06:18,400 electrons out of them. And so you produce individual 112 00:06:18,700 --> 00:06:22,900 ions and so, you're going from a solid piece of mineral all the 113 00:06:22,900 --> 00:06:26,000 way through to individual ions and essentially the The laser 114 00:06:26,000 --> 00:06:29,500 does the initial part of that process by taking into small 115 00:06:29,500 --> 00:06:32,600 particles, but the islands themselves are made actually 116 00:06:32,600 --> 00:06:37,800 inside that argon plasma. Okay, so you'll get a spot of a 117 00:06:37,800 --> 00:06:41,300 laser onto a sample, get a fatty good spatial resolution because 118 00:06:41,300 --> 00:06:45,200 of the size of the laser beam, which is pretty small about 10 119 00:06:45,200 --> 00:06:48,900 to 30 microns and then you can get it into a mass spectrometer. 120 00:06:48,900 --> 00:06:54,000 So why did these instruments that already existed? 121 00:06:54,000 --> 00:06:56,900 Not adequately. The challenges that I mentioned 122 00:06:56,900 --> 00:07:00,500 earlier, namely the amount of labor involved and the problem 123 00:07:00,600 --> 00:07:04,100 of making geochronology and geochemistry results consistent 124 00:07:04,100 --> 00:07:07,200 with each other. So typically these laser 125 00:07:07,200 --> 00:07:12,000 instruments have been in use since around 1995 or so, but 126 00:07:12,000 --> 00:07:15,500 those early instruments and actually up until relatively 127 00:07:15,500 --> 00:07:18,900 recently would either measure the age of a mineral, or they 128 00:07:18,900 --> 00:07:21,100 would measure the trace element concentrations. 129 00:07:21,400 --> 00:07:24,000 Only relatively recently. Have we figured out how to 130 00:07:24,000 --> 00:07:27,200 measure both the ages? Has as well as the trace element 131 00:07:27,200 --> 00:07:31,100 concentrations together on the same volume of material and 132 00:07:31,100 --> 00:07:34,500 really the advances come from new generations of instruments 133 00:07:34,500 --> 00:07:37,500 that are more sensitive and having a better ability to 134 00:07:37,500 --> 00:07:39,500 separate out those different ions. 135 00:07:39,500 --> 00:07:42,500 And so the better sensitivity allows us to use smaller spot 136 00:07:42,500 --> 00:07:46,200 size but also measure those. Trace elements that are in sub 137 00:07:46,200 --> 00:07:49,300 PPM concentrations, things that we simply couldn't detect 138 00:07:49,500 --> 00:07:52,000 because of the sensitivity of those early instruments. 139 00:07:52,100 --> 00:07:55,500 But from what, I gather those instruments have to be used. 140 00:07:55,700 --> 00:07:57,900 Separate phases. You did the two separate 141 00:07:57,900 --> 00:08:01,700 analyses in two separate phases and so you still went quite sure 142 00:08:02,000 --> 00:08:05,000 if you were actually dealing with the same actual sample. 143 00:08:05,300 --> 00:08:07,600 That's right. And so typically, when I did my 144 00:08:07,600 --> 00:08:10,200 PhD and I did a lot of laser ablation analyses. 145 00:08:10,200 --> 00:08:12,300 The first thing I would do is I would take my sample to an 146 00:08:12,300 --> 00:08:15,300 electron microprobe and I would measure the major and Trace 147 00:08:15,300 --> 00:08:18,500 elements in those minerals. And I would then take my sample 148 00:08:18,500 --> 00:08:20,800 to a laser ablation system and measure the age. 149 00:08:20,900 --> 00:08:23,300 And so, we could never be entirely sure. 150 00:08:23,300 --> 00:08:25,500 That we were measuring exactly the same. 151 00:08:25,600 --> 00:08:28,500 Mmmmm composition or the same domain within a crystal. 152 00:08:28,500 --> 00:08:31,800 And so there's always this mismatch between the different 153 00:08:31,800 --> 00:08:34,000 data that you generate from the different instruments. 154 00:08:34,200 --> 00:08:35,500 Yeah. And as I mentioned in the 155 00:08:35,500 --> 00:08:37,400 introduction, that can be quite a big problem. 156 00:08:37,400 --> 00:08:40,700 If there are variations across a crystal on a fairly small 157 00:08:40,700 --> 00:08:43,299 spatial scale, which is often the case, especially in the kind 158 00:08:43,299 --> 00:08:46,500 of complex situations that you're trying to unravel. 159 00:08:46,500 --> 00:08:49,100 I imagine. So how did you overcome this 160 00:08:49,100 --> 00:08:51,300 problem? So instead of doing sequential 161 00:08:51,300 --> 00:08:54,700 measurements, what we did is we took to mass spectrometers and 162 00:08:54,700 --> 00:08:57,800 we took the Stream of particles that comes from a laser and we 163 00:08:57,800 --> 00:09:01,100 took their stereo particles. And we split that stream of 164 00:09:01,100 --> 00:09:03,100 particles. We sent them simultaneously to 165 00:09:03,100 --> 00:09:05,500 to mass spectrometers. So one Mass spectrometer would 166 00:09:05,500 --> 00:09:08,800 measure the age and the other Mass spectrometer would measure 167 00:09:08,800 --> 00:09:12,900 the trace element concentrations or other isotopic traces. 168 00:09:13,000 --> 00:09:15,900 For example, like hafnium and zirconium or neodymium and 169 00:09:15,900 --> 00:09:19,100 monocyte things like that. But an isotopic or Elemental 170 00:09:19,100 --> 00:09:22,400 Tracer along with the age of the mineral. 171 00:09:22,900 --> 00:09:26,500 The real advantage of that then is that you You can be certain 172 00:09:26,500 --> 00:09:30,800 that the age you're getting has coupled directly to some form of 173 00:09:30,800 --> 00:09:32,800 Trace element or isotopic Tracer. 174 00:09:33,400 --> 00:09:37,400 And so when you get an age you get a direct correlation between 175 00:09:37,400 --> 00:09:40,700 those other crucial indicators of what the age actually means 176 00:09:40,700 --> 00:09:43,700 and a geologic context. That's brilliant. 177 00:09:43,700 --> 00:09:46,100 You have one laser. And then what comes off you 178 00:09:46,100 --> 00:09:48,800 split into two streams. So it's coming from the same 179 00:09:48,800 --> 00:09:51,400 spot so there's absolutely no difference between what's going 180 00:09:51,400 --> 00:09:54,300 into the age determination. And what's going into the 181 00:09:54,700 --> 00:09:57,500 geochemical? Trace element, determination. 182 00:09:57,900 --> 00:09:59,800 When I put it like that it seems kind of obvious. 183 00:09:59,900 --> 00:10:02,300 Why did nobody do it before, was it very difficult? 184 00:10:02,700 --> 00:10:05,100 There's a couple of things that prevented people doing. 185 00:10:05,100 --> 00:10:08,500 This earlier one is simply the cost involved of having to mass 186 00:10:08,500 --> 00:10:11,500 spectrometers in the same laboratory space. 187 00:10:11,500 --> 00:10:13,600 There's a bunch of infrastructure issues. 188 00:10:13,600 --> 00:10:16,200 The amount of gas that gets used the power supplies that are 189 00:10:16,200 --> 00:10:19,700 necessary. The other part of that is that 190 00:10:19,700 --> 00:10:22,900 only relatively recently in the last decade or so that we've 191 00:10:22,900 --> 00:10:25,000 actually been able to get the instruments with. 192 00:10:25,500 --> 00:10:28,900 Sensitivity such that when you reduce the amount of material by 193 00:10:28,900 --> 00:10:31,900 a half when you split it to to mass spectrometers that you 194 00:10:31,900 --> 00:10:34,900 still get sufficient amounts of signal to actually measure those 195 00:10:34,900 --> 00:10:37,500 concentrations and those isotopic, ratios add a 196 00:10:37,800 --> 00:10:40,500 Precision, that's good enough to solve the geologic. 197 00:10:40,500 --> 00:10:44,600 Problem is this dream coming from a laser split up as soon as 198 00:10:44,600 --> 00:10:48,400 it comes off the sample. So the way the laser system 199 00:10:48,400 --> 00:10:51,800 works is the sample is at atmospheric pressure, and so the 200 00:10:51,800 --> 00:10:55,200 laser samples, the material atmospheric pressure, but it's 201 00:10:55,200 --> 00:10:58,800 in a Liam atmosphere. So we have an enclosed cell or 202 00:10:58,800 --> 00:11:02,900 chamber, and we pump that chamber with helium gas, and 203 00:11:02,900 --> 00:11:06,200 that helium gas essentially, takes that aerosol material, 204 00:11:06,200 --> 00:11:09,700 that's being ablated and extract it from the cell, and then we 205 00:11:09,700 --> 00:11:12,700 mixed that helium and that sample with some Argon gas and 206 00:11:12,700 --> 00:11:14,500 that drives it into the mass spectrometer. 207 00:11:15,200 --> 00:11:18,600 So, the useful thing about that process is that it's relatively 208 00:11:18,600 --> 00:11:21,400 quick in the sense that every time, the laser hits the sample 209 00:11:21,400 --> 00:11:24,600 at excavates, a small amount of sample and we immediately remove 210 00:11:24,600 --> 00:11:27,000 that sample. Or that material from the sample 211 00:11:27,000 --> 00:11:30,800 site and so you can actually get relatively good spatial 212 00:11:30,800 --> 00:11:33,700 resolution by rapidly. Removing that material, as you 213 00:11:33,700 --> 00:11:36,800 go down a whole or as you go along a crystal. 214 00:11:37,000 --> 00:11:40,000 And so, when I say rapidly, I'm talking about much less than a 215 00:11:40,000 --> 00:11:43,600 second between the material, being a ejected, from the sample 216 00:11:43,600 --> 00:11:45,700 site and it reaching the mass spectrometer. 217 00:11:45,700 --> 00:11:49,000 So you get relatively good to depth, resolution as well as 218 00:11:49,000 --> 00:11:52,000 good spatial resolution in the x y direction. 219 00:11:52,200 --> 00:11:54,800 I'm impressed that you can go from an atmospheric type 220 00:11:54,800 --> 00:11:58,100 pressure of will It filled with helium and introduce Argan. 221 00:11:58,600 --> 00:12:01,500 But inside the mass spectrometer itself, you have a very hard 222 00:12:01,500 --> 00:12:03,200 vacuum, don't you? That's right. 223 00:12:03,200 --> 00:12:06,400 So inductively couple plasma has are unique in that sense that 224 00:12:06,400 --> 00:12:08,900 the sample starts at atmospheric pressure. 225 00:12:08,900 --> 00:12:12,500 And then there's a rapid decrease in pressure across that 226 00:12:12,500 --> 00:12:16,200 Supple interface and that plasma interface to get down to 10 to 227 00:12:16,200 --> 00:12:19,600 the minus 9 or 10 to the minus 10, millibars to actually be 228 00:12:19,600 --> 00:12:21,900 able to get those ions to travel to the detector. 229 00:12:21,900 --> 00:12:25,900 So, part of the thing, we really focused on was trying to 230 00:12:25,900 --> 00:12:28,400 understand how those vacuum systems can be improved. 231 00:12:28,400 --> 00:12:30,600 And we spent a lot of time working with mass spectrometry 232 00:12:30,600 --> 00:12:34,100 companies to actually make those vacuum systems a lot better and 233 00:12:34,100 --> 00:12:36,800 the better you make the vacuum, the better, the sensitivity of 234 00:12:36,800 --> 00:12:39,000 the instrument, alternatively, if you want to think about it, 235 00:12:39,000 --> 00:12:42,100 another way, if you have enough signal, you can actually use a 236 00:12:42,100 --> 00:12:44,100 smaller spot size. In other words, use less 237 00:12:44,100 --> 00:12:45,900 material for the same amount of precision. 238 00:12:45,900 --> 00:12:49,000 So depending on what you're trying to do, we really isolated 239 00:12:49,000 --> 00:12:51,900 the biggest Improvement we could make really was to that vacuum 240 00:12:51,900 --> 00:12:53,600 system. And so we spent a lot of time 241 00:12:53,700 --> 00:12:58,100 trying to develop that what Minerals are amenable to this 242 00:12:58,200 --> 00:13:03,100 laser ablation split stream technique and do use different 243 00:13:03,100 --> 00:13:05,900 minerals because sometimes a rock will only have one of 244 00:13:05,900 --> 00:13:07,500 those. And so you just have to use what 245 00:13:07,500 --> 00:13:11,300 you've got or because each mineral can provide information 246 00:13:11,600 --> 00:13:14,200 on something different about the Rocks history. 247 00:13:14,200 --> 00:13:17,000 We really try to tailor the mineral, we measure to the 248 00:13:17,000 --> 00:13:18,400 problem. We're trying to answer. 249 00:13:18,500 --> 00:13:21,200 For example, in igneous, systems will often use Zircon because 250 00:13:21,200 --> 00:13:23,200 that's the primary carrier of uranium. 251 00:13:24,000 --> 00:13:27,200 But in other geologic, Systems, for example, metamorphic rocks 252 00:13:27,200 --> 00:13:31,000 will often measure the monocyte and the appetite the Xena time 253 00:13:31,000 --> 00:13:34,000 and maybe the titanate as well. And the reasons for that are 254 00:13:34,008 --> 00:13:37,600 primarily that they may tell us about different parts of the 255 00:13:37,600 --> 00:13:39,200 metamorphic history of that rock. 256 00:13:39,500 --> 00:13:42,800 But also they tend to taken Trace elements at different 257 00:13:42,800 --> 00:13:46,000 concentrations because of the compositions of those minerals 258 00:13:46,600 --> 00:13:48,300 and so different. Trace elements might tell us 259 00:13:48,300 --> 00:13:50,500 different things about how those rocks evolved. 260 00:13:50,500 --> 00:13:55,200 If the mineral has about half to about 1, PPM uranium. 261 00:13:55,500 --> 00:13:59,300 And it has some ready Jake lead in it and that's not swamped by 262 00:13:59,300 --> 00:14:02,600 Common lead, then we can usually measure an age. 263 00:14:02,800 --> 00:14:05,800 And if the mineral has greater than about half a PPM of any 264 00:14:05,800 --> 00:14:08,400 Trace element, we can use you measure that to relatively good 265 00:14:08,400 --> 00:14:11,500 precision as well. So this new term that we're 266 00:14:11,500 --> 00:14:14,400 using in connection with the simultaneous measurement of the 267 00:14:14,500 --> 00:14:18,200 age and the trace element abundances is petrol chronology. 268 00:14:18,300 --> 00:14:21,700 So I understand the chronology bit because we've talked a lot 269 00:14:21,700 --> 00:14:24,800 on the podcast earlier about uranium-lead dating of zircons 270 00:14:24,800 --> 00:14:29,300 and You get a date from the ratio of the daughter nuclides 271 00:14:29,300 --> 00:14:31,300 to the parent, nuclides, roughly speaking. 272 00:14:31,300 --> 00:14:34,300 And, and with uranium LED, you have two clocks, so that makes 273 00:14:34,300 --> 00:14:37,400 it even better. But on the petrol side if you 274 00:14:37,408 --> 00:14:40,700 like or only Trace element abundance measurement side. 275 00:14:41,200 --> 00:14:45,200 What exactly does that tell you about the Crystal and about the 276 00:14:45,200 --> 00:14:48,500 rock within, which it Formed. Yeah, so one of the challenges 277 00:14:48,500 --> 00:14:51,700 we've faced with minimal Fat Rocks but also with igneous 278 00:14:51,700 --> 00:14:55,100 rocks, as well as if you have a date or a series of dates from a 279 00:14:55,108 --> 00:14:57,100 mineral. Or different minerals in a rock. 280 00:14:57,200 --> 00:14:59,900 The fundamental question is, what does that date mean in the 281 00:14:59,900 --> 00:15:02,500 context of that rock and in the context of the broader? 282 00:15:02,900 --> 00:15:06,000 Geology and so in a minute, morphic Rock, if you were to 283 00:15:06,000 --> 00:15:09,700 date a monocyte, for example, you might typically see ranges 284 00:15:09,700 --> 00:15:13,500 of Ages, that might be five to maybe 10 or 20 million years 285 00:15:13,500 --> 00:15:16,300 spread within an individual Crystal, or with an individual 286 00:15:16,300 --> 00:15:18,900 Rock. For example, monocyte is a great 287 00:15:18,900 --> 00:15:22,700 mineral because it takes in Rare Earth elements and those Rare 288 00:15:22,700 --> 00:15:25,100 Earth elements can be used to tell you about what else is 289 00:15:25,100 --> 00:15:26,500 happening. Burning in that rock. 290 00:15:26,500 --> 00:15:29,300 For example, the mineral Garnet has a big control on the rear 291 00:15:29,300 --> 00:15:33,200 Earth element budget of a rock and so if a guarded is growing 292 00:15:33,200 --> 00:15:36,100 it will compete with monocyte for Rare Earth elements and so 293 00:15:36,100 --> 00:15:39,000 if we think about the way Rare Earth elements are partitioned 294 00:15:39,000 --> 00:15:43,700 between Say Ghana and monocyte. Then if Garnet is growing the 295 00:15:43,700 --> 00:15:46,500 monocyte that grows at the same time might well be depleted in 296 00:15:46,500 --> 00:15:49,700 certain Trace elements. You can think about the trace 297 00:15:49,700 --> 00:15:52,700 elements in your mineral as being a reflection of what's 298 00:15:52,700 --> 00:15:55,200 going on in the geochemistry of The Rock. 299 00:15:55,500 --> 00:15:58,400 The petrology of that rock. And so, being able to make a 300 00:15:58,408 --> 00:16:01,800 quantitative link between your date and your Trace element, 301 00:16:01,800 --> 00:16:04,100 concentrations to what's happening in the Rock allows you 302 00:16:04,108 --> 00:16:08,000 to tie it to, for example, things like defamation, but also 303 00:16:08,000 --> 00:16:10,400 the pressure, temperature conditions have been a morphism 304 00:16:10,400 --> 00:16:13,400 and you can do a similar kind of thing and igneous rocks as well. 305 00:16:13,400 --> 00:16:15,800 If you understand something about the phase relationships, 306 00:16:16,000 --> 00:16:19,300 amongst different minerals. So really the key is to take it 307 00:16:19,300 --> 00:16:21,500 from a qualitative interpretation, which is what 308 00:16:21,500 --> 00:16:24,100 people were doing previously to making some quantitative 309 00:16:24,100 --> 00:16:27,800 estimates of what the The conditions of that age, actually 310 00:16:27,800 --> 00:16:29,700 are relative to the history of that rock. 311 00:16:29,700 --> 00:16:31,500 Oh, I see. So just to expand on the 312 00:16:31,500 --> 00:16:35,500 example, you gave with Garnet. If you can identify that at a 313 00:16:35,508 --> 00:16:40,200 particular age, there was a certain depletion in certain 314 00:16:40,200 --> 00:16:42,300 Rare Earth elements that you're measuring. 315 00:16:42,700 --> 00:16:46,400 You would infer that Garnet was growing at that time in that 316 00:16:46,400 --> 00:16:50,000 rock or from that melt. And therefore the fact that 317 00:16:50,000 --> 00:16:53,500 Garnet is growing tells you something about where you are on 318 00:16:53,500 --> 00:16:55,900 the pressure temperature graph, It's right. 319 00:16:55,900 --> 00:16:58,900 So one really good example, is the element Atrium. 320 00:16:59,100 --> 00:17:02,400 If you take a metamorphic rock and as you minimal, foes that 321 00:17:02,400 --> 00:17:03,900 rock. You increase the pressure, you 322 00:17:03,900 --> 00:17:08,000 increase the temperature and as The Rock gets to maybe about 500 323 00:17:08,000 --> 00:17:11,000 degrees or so, monocyte might, well start to crystallize and it 324 00:17:11,000 --> 00:17:13,400 might start to crystallize either at the same time or 325 00:17:13,400 --> 00:17:17,099 potentially, even earlier than garnets dust to nucleate any 326 00:17:17,099 --> 00:17:20,700 monocyte that grows prior to any gun at forming will be 327 00:17:20,700 --> 00:17:24,300 relatively enriched in the element yttrium and so earlier 328 00:17:24,300 --> 00:17:27,200 formed monocyte would Be relatively high in a tree. 329 00:17:27,200 --> 00:17:30,600 Mm, but then if you continue to metamorphose that rock and you 330 00:17:30,600 --> 00:17:34,400 nucleate Garnet that Garnet will tend to take up most of the 331 00:17:34,400 --> 00:17:37,500 Eritrean, The Rock. And so any monocyte that grows 332 00:17:37,500 --> 00:17:39,900 will be relatively depleted in Atrium. 333 00:17:40,700 --> 00:17:45,100 And so you can track the growth of Garnet in that rock by 334 00:17:45,100 --> 00:17:48,600 actually looking at the yttrium concentration of the monocyte 335 00:17:49,200 --> 00:17:52,200 and often what you'll see is at the very end of the metamorphic 336 00:17:52,200 --> 00:17:53,600 cycle. Some of that Garnet might 337 00:17:53,600 --> 00:17:56,300 actually start to break down or I will It'll be the rock, might 338 00:17:56,300 --> 00:17:59,200 start to melt, but in either case, you might see breakdown of 339 00:17:59,200 --> 00:18:02,000 garnet. And so that liberates a bunch of 340 00:18:02,000 --> 00:18:05,200 yttrium and any monocyte that grows during that period will be 341 00:18:05,200 --> 00:18:07,600 relatively enriched in a tree. And there's a bunch of interim 342 00:18:07,600 --> 00:18:10,000 available in the system. And so, the monocyte will take 343 00:18:10,000 --> 00:18:13,300 that up and so you can make a link between the atrium 344 00:18:13,300 --> 00:18:16,100 concentration or the other Rare Earth elements between your 345 00:18:16,100 --> 00:18:18,800 Manas 8th Annual Garnet. Now, there are complications 346 00:18:18,800 --> 00:18:21,000 because there are other minerals in the Rock, which you also have 347 00:18:21,000 --> 00:18:24,100 yttrium and them for examples in a team or appetite. 348 00:18:24,800 --> 00:18:27,100 But if you know, do something about the modal abundances of 349 00:18:27,100 --> 00:18:30,800 those other minerals, you can then start to calculate what the 350 00:18:30,800 --> 00:18:34,100 effect of those minerals might be but the principle really is 351 00:18:34,100 --> 00:18:38,100 to try and get at whereabouts. Are you on that minimal for 352 00:18:38,300 --> 00:18:40,700 path? In both your monocyte and as 353 00:18:40,700 --> 00:18:42,800 well as your garnet and then you can calculate the pressure 354 00:18:42,800 --> 00:18:45,500 temperature conditions you can calculate the age and you can 355 00:18:45,500 --> 00:18:48,200 then get a rate and that's fundamentally what most people 356 00:18:48,200 --> 00:18:50,700 really care about when they think about metamorphic. 357 00:18:50,700 --> 00:18:53,300 Rocks is the absolute conditions are minimal for them but then 358 00:18:53,300 --> 00:18:55,300 also the rates of that process as well. 359 00:18:55,400 --> 00:18:58,100 It's the right that we dominantly care about in terms 360 00:18:58,100 --> 00:19:00,400 of s scale of it geologic process. 361 00:19:00,900 --> 00:19:04,400 How long does it take you to obtain a date and it Trace 362 00:19:04,400 --> 00:19:07,600 element abundance measurement for a particular location within 363 00:19:07,600 --> 00:19:10,200 a crystal. An individual sport can take 364 00:19:10,200 --> 00:19:14,300 anywhere from five seconds to about 20 seconds to measure so 365 00:19:14,300 --> 00:19:18,100 that would give you one analysis for a typical monocyte that 366 00:19:18,100 --> 00:19:20,500 maybe has 3 or 4 different age domains. 367 00:19:20,500 --> 00:19:23,600 We might make 2240 measurements on an individual. 368 00:19:23,600 --> 00:19:26,300 One has a crystal and Or an individual Rock. 369 00:19:26,300 --> 00:19:28,500 We might measure 10 to 12 miles out crystals. 370 00:19:28,500 --> 00:19:31,900 So we might end up with on the order of 100 to 200 analysis per 371 00:19:31,900 --> 00:19:34,600 sample, and that might take one to three hours. 372 00:19:34,600 --> 00:19:37,100 By the time, you measure some, secondary standards, and some 373 00:19:37,100 --> 00:19:39,800 primary calibration materials as well to make sure you're getting 374 00:19:39,800 --> 00:19:42,800 a precise and accurate Point. That's incredible compared to 375 00:19:42,800 --> 00:19:46,400 weeks and weeks of work for one single family and ization. 376 00:19:46,400 --> 00:19:50,800 Mass spectrometry measurement, Toki different style of working. 377 00:19:50,900 --> 00:19:53,900 That's right. So, when you want to unravel, 378 00:19:53,900 --> 00:19:57,000 say, the history of An entire outcrop. 379 00:19:57,300 --> 00:19:59,300 How many mineral grains would you typically use? 380 00:19:59,300 --> 00:20:02,100 And how many spot measurements would be used for a typical 381 00:20:02,100 --> 00:20:04,300 outcrop? You might date maybe four to 382 00:20:04,300 --> 00:20:06,000 five rocks. We would date the metamorphic 383 00:20:06,000 --> 00:20:07,800 rocks prison. And if they're at cross-cutting 384 00:20:07,800 --> 00:20:09,600 igneous rocks, you might date those as well. 385 00:20:10,300 --> 00:20:14,000 And so typically within a day or so, a 12-hour day on the 386 00:20:14,000 --> 00:20:17,400 instrument, you might be able to date 526 rocks. 387 00:20:17,700 --> 00:20:20,500 Really the limitation of this technique is how long are you 388 00:20:20,500 --> 00:20:22,100 prepared to run the instrument for? 389 00:20:22,100 --> 00:20:24,500 We have people who come to our lab and they'll be essentially 390 00:20:24,500 --> 00:20:27,100 awake for Four hours a day for seven days a week. 391 00:20:27,500 --> 00:20:30,900 And in that time, you can get literally thousands to several 392 00:20:30,900 --> 00:20:32,800 thousand. Analyses offer a range of 393 00:20:32,800 --> 00:20:36,300 different rocks. Now it's great because the more 394 00:20:36,300 --> 00:20:38,800 data you have the bigger picture, you see, but that comes 395 00:20:38,800 --> 00:20:40,800 at a cost and you mentioned thermal ionization Mass 396 00:20:40,800 --> 00:20:42,500 spectrometry. So I think it's really important 397 00:20:42,500 --> 00:20:45,300 to note that both of those techniques have really important 398 00:20:45,300 --> 00:20:46,900 parts to play. If you want the ultimate 399 00:20:46,900 --> 00:20:50,600 Precision date, then you will never beat a thermal ionization, 400 00:20:50,600 --> 00:20:52,800 Mass spectrometry date. They're the most precise. 401 00:20:52,800 --> 00:20:56,200 They're the most accurate. And instead what As we tried 402 00:20:56,200 --> 00:20:58,700 some of that accuracy, we trade some of that Precision for 403 00:20:58,700 --> 00:21:01,300 number of analyses. And for that special resolution, 404 00:21:01,300 --> 00:21:04,900 we can measure individual parts of a crystal and so I hear a lot 405 00:21:04,908 --> 00:21:07,700 of people in the community. They have one or the other, but 406 00:21:07,700 --> 00:21:10,000 to me, they're both tools. And depending on the question, 407 00:21:10,000 --> 00:21:13,000 you want to answer, you should choose one or the other or 408 00:21:13,000 --> 00:21:16,300 ideally you might use both. Can you give us some examples of 409 00:21:16,300 --> 00:21:19,700 how the use of this bitstream method has enabled us to 410 00:21:19,700 --> 00:21:23,600 deconvolve? Some metamorphic histories that 411 00:21:23,600 --> 00:21:25,800 were Out Of Reach with the Methods. 412 00:21:26,400 --> 00:21:29,200 Yes, most of my research over the last 20 years, or so has 413 00:21:29,200 --> 00:21:32,200 been focused on the Himalaya and really trying to understand the 414 00:21:32,200 --> 00:21:34,800 metamorphic history of the Himalaya, but also the magmatic 415 00:21:34,800 --> 00:21:38,500 history as well and the spatial scales of metamorphism and 416 00:21:38,600 --> 00:21:41,000 melting as well. And so, when I first started out 417 00:21:41,000 --> 00:21:44,500 of my PhD, we really considered the mid crustal rocks in the 418 00:21:44,508 --> 00:21:48,100 Himalaya, these rocks the, the greater Himalayan series, these 419 00:21:48,100 --> 00:21:50,200 rocks, make up the highest peaks of the Himalaya. 420 00:21:50,800 --> 00:21:54,100 And we always imagined that there was this 20 to 40 km, 421 00:21:54,100 --> 00:21:56,700 thick sequence of this. High grade metamorphic rocks 422 00:21:56,700 --> 00:22:00,100 that formed a pretty coherent package but subsequent to that 423 00:22:00,100 --> 00:22:02,600 we've dated literally hundreds to thousands of these 424 00:22:02,600 --> 00:22:04,800 metamorphic, rocks with collaborators across the 425 00:22:04,800 --> 00:22:08,500 orogenic front and we realize that actually, the internal 426 00:22:08,600 --> 00:22:11,200 structure of that series of mood crustal. 427 00:22:11,200 --> 00:22:14,900 Rocks is a lot more complicated. And I think we only really were 428 00:22:14,900 --> 00:22:17,900 able to figure that out by literally dating, tens of rocks 429 00:22:17,900 --> 00:22:21,300 on an individual transect and then doing multiple transects 430 00:22:21,300 --> 00:22:23,900 across different parts of the Himalaya and you start to see 431 00:22:23,900 --> 00:22:27,200 that the timing of metamorphism is subtly different, but also 432 00:22:27,200 --> 00:22:29,600 the conditions of metamorphism a subtly different. 433 00:22:29,600 --> 00:22:33,100 And so not only can you see differences in when these rocks 434 00:22:33,100 --> 00:22:35,400 are metamorphosed, but we're in the crust, they would be in a 435 00:22:35,408 --> 00:22:38,100 more focused and how they were juxtaposed against one another. 436 00:22:38,800 --> 00:22:42,200 And if I think about my PhD, I dated I think something like 15 437 00:22:42,200 --> 00:22:44,800 rocks. It took me 34 years of really 438 00:22:44,800 --> 00:22:48,800 hard work to do that and then we would go back 5 or 10 years 439 00:22:48,800 --> 00:22:51,400 later with this new technique, we could date that number of 440 00:22:51,400 --> 00:22:53,400 rocks in an afternoon on the instrument. 441 00:22:53,400 --> 00:22:56,200 And so with a really concerted effort, Get large amounts of 442 00:22:56,200 --> 00:22:59,300 data and only then, do you actually start to see that 443 00:22:59,300 --> 00:23:02,100 really fine scale resolution of how that mid crust was 444 00:23:02,100 --> 00:23:04,200 constructed? It really changed the way I 445 00:23:04,208 --> 00:23:07,100 thought about how you actually make the mid crushed in the 446 00:23:07,100 --> 00:23:08,700 Himalaya. It's not really this. 447 00:23:08,700 --> 00:23:11,700 Homogeneous package of metamorphic rocks, actually has 448 00:23:11,700 --> 00:23:14,100 a significant amount of variation and that you only 449 00:23:14,100 --> 00:23:16,800 really are able to see when you actually get these really large 450 00:23:16,900 --> 00:23:20,100 data sets that link the geochemistry and therefore the 451 00:23:20,100 --> 00:23:22,400 conditions of metamorphism to those ages. 452 00:23:22,700 --> 00:23:25,100 Do we have an understanding yet of what caused that? 453 00:23:25,300 --> 00:23:29,000 That heterogeneity within the greater Himalayan series, one 454 00:23:29,000 --> 00:23:32,200 way of considering, it is when you make the mid crust or when 455 00:23:32,200 --> 00:23:36,000 you alter them at crossed, there might actually be a series of 456 00:23:36,000 --> 00:23:39,400 stacks of thrust slices that get accumulated relative to one 457 00:23:39,400 --> 00:23:41,100 another. And when you take those stress 458 00:23:41,100 --> 00:23:43,900 slices and you put them together, you then take all of 459 00:23:43,908 --> 00:23:46,900 that material and you start to extrude it Southward towards the 460 00:23:46,900 --> 00:23:50,400 Indian front. We imagine that that process of 461 00:23:50,400 --> 00:23:53,100 taking that made crust. And moving it Southward over, 462 00:23:53,100 --> 00:23:57,100 the subcommittee are happened is Parent block was actually, I 463 00:23:57,108 --> 00:23:59,900 think we see now is that it's happening at a finer scale. 464 00:23:59,900 --> 00:24:02,000 There are individuals thrust sheets, that are actually being 465 00:24:02,000 --> 00:24:05,400 moved relative to one another to then accumulate together to 466 00:24:05,400 --> 00:24:09,300 produce that McChrystal package. And so to me it's a question of 467 00:24:09,300 --> 00:24:11,000 scale. We thought it was one giant 468 00:24:11,000 --> 00:24:13,500 package of rocks and now I think we realize that actually it's 469 00:24:13,500 --> 00:24:16,100 smaller packages with their own individual histories, which we 470 00:24:16,108 --> 00:24:20,500 can start to tease out there any other examples of places where 471 00:24:20,500 --> 00:24:24,500 you've applied these methods, there are working on subduction 472 00:24:24,500 --> 00:24:26,600 related. Nice rocks in Antarctica. 473 00:24:26,900 --> 00:24:29,600 Antarctica is incredibly difficult place to get to, but 474 00:24:29,700 --> 00:24:32,800 there is a really large number of rocks available from people 475 00:24:32,800 --> 00:24:36,100 who have previously been to Antarctica and many of those 476 00:24:36,100 --> 00:24:39,200 rocks were dated by isotope dilution techniques, is that the 477 00:24:39,200 --> 00:24:40,600 same? As the thermal ionization 478 00:24:40,600 --> 00:24:41,900 method? We were talking about earlier, 479 00:24:42,000 --> 00:24:43,100 that's right. Yes. 480 00:24:43,400 --> 00:24:45,900 And the problem with those minerals is particularly the 481 00:24:45,900 --> 00:24:47,700 Antarctic. Granite's are relatively high in 482 00:24:47,700 --> 00:24:51,600 uranium. And so prior to the mid 2000s, 483 00:24:51,600 --> 00:24:54,700 one of the main limiting factors of thermal ionization technique 484 00:24:54,700 --> 00:24:56,700 was that Feels Iran has led loss. 485 00:24:56,700 --> 00:25:00,200 If it has high uranium and the crystal lattice is damaged, then 486 00:25:00,600 --> 00:25:03,700 that accumulated rated eunuch LED can leak out of the Crystal. 487 00:25:03,800 --> 00:25:06,800 And so, when you measure the uranium-lead ratio, that date is 488 00:25:06,800 --> 00:25:09,200 younger than you might expect, because it's lost that daughter 489 00:25:09,200 --> 00:25:12,100 product. And so a lot of those dates were 490 00:25:12,100 --> 00:25:14,700 really imprecise or they were subject to lead loss. 491 00:25:15,000 --> 00:25:18,200 Now, the useful thing about the laser technique is that when you 492 00:25:18,200 --> 00:25:21,100 take a look at your Crystal, you can actually isolate domains. 493 00:25:21,100 --> 00:25:23,200 That have undergone led loss and domains. 494 00:25:23,200 --> 00:25:24,500 That have not undergone their lies. 495 00:25:24,500 --> 00:25:27,100 You can see it, When you do multiple spots and individual 496 00:25:27,100 --> 00:25:28,900 Crystal. And so you can essentially 497 00:25:28,900 --> 00:25:31,500 eliminate any of the domains of underground lead Lawson only 498 00:25:31,500 --> 00:25:35,600 select the parts of your Crystal that are concordant or where 499 00:25:35,600 --> 00:25:37,900 there's been no disturbance to the uranium lead system. 500 00:25:38,500 --> 00:25:41,000 And so in Antarctica, we were able to date several hundred 501 00:25:41,000 --> 00:25:44,500 rocks across the orogenic front and essentially eliminate all of 502 00:25:44,500 --> 00:25:47,100 that led loss and really get at the truth timing of igneous 503 00:25:47,100 --> 00:25:49,100 intrusion. But also, the duration of that 504 00:25:49,100 --> 00:25:52,400 metamorphism, we're kind of we're able to redefine what the 505 00:25:52,400 --> 00:25:53,900 history of magnetism in Antarctica. 506 00:25:53,900 --> 00:25:58,300 Looks like the The time scales of magnetism and Link that to 507 00:25:58,300 --> 00:26:02,600 things like hafnium Isotopes in the same analyze volume that 508 00:26:02,600 --> 00:26:05,200 would allow us to understand the sources of those Magma's but 509 00:26:05,200 --> 00:26:07,800 also the processes that might modify those Magma's. 510 00:26:08,000 --> 00:26:10,800 So from an individual spot, we would get the age but also the 511 00:26:10,800 --> 00:26:14,500 isotopic composition and we could then say something about 512 00:26:14,500 --> 00:26:16,600 these rocks. Are they dominated by mental 513 00:26:16,600 --> 00:26:19,900 components, or they're dominated by recycling of old crust? 514 00:26:20,100 --> 00:26:22,500 People argue a lot about subduction zones, whether they 515 00:26:22,500 --> 00:26:25,100 represent sites of crustal, recycling or crosstalk? 516 00:26:25,200 --> 00:26:27,200 Growth. But unless you have those really 517 00:26:27,200 --> 00:26:30,300 precise age, constraints, coupled to some isotope Tracer, 518 00:26:30,700 --> 00:26:32,300 it's really difficult to get at that. 519 00:26:32,300 --> 00:26:35,400 So, that's another area that we're really done this campaign 520 00:26:35,400 --> 00:26:38,100 style, geochronology of literally hundreds of dates, 521 00:26:38,400 --> 00:26:41,900 across, thousands of kilometers of section to really get at what 522 00:26:41,900 --> 00:26:44,700 that magnetic history looks like what period are we talking about 523 00:26:44,700 --> 00:26:48,200 in Antarctica, the magnetic rocks Antarctica range from 524 00:26:48,200 --> 00:26:52,500 about 560 million years all the way through to about 490 million 525 00:26:52,500 --> 00:26:54,200 years. Most of the magnetism ranges 526 00:26:54,200 --> 00:26:58,400 between about 15 in about 490. But one of the interesting 527 00:26:58,400 --> 00:27:00,900 things were actually able to show is that magnetism is much 528 00:27:00,900 --> 00:27:03,600 older and much younger than we previously thought because much 529 00:27:03,600 --> 00:27:06,900 of that variation is hidden by that led last that was in those 530 00:27:06,900 --> 00:27:10,000 older analyses. And so with the laser technique 531 00:27:10,000 --> 00:27:12,900 you can see older magnetism that's concordant and you can 532 00:27:12,900 --> 00:27:14,900 see younger dates that are concordant as well. 533 00:27:14,900 --> 00:27:18,100 But yeah, roughly that kind of Canberra ordovician period. 534 00:27:18,500 --> 00:27:22,700 Are you working on any other parts of the world with these 535 00:27:22,700 --> 00:27:25,600 techniques? We're trying to think about 536 00:27:25,600 --> 00:27:29,700 other places on the planet where we see metamorphic rocks that 537 00:27:29,700 --> 00:27:32,500 either have more than one phase of metamorphism and have 538 00:27:32,500 --> 00:27:35,900 previously been either interpreted in the light of 539 00:27:35,900 --> 00:27:38,700 dates or ages, that may be mixtures of those multiple 540 00:27:38,700 --> 00:27:42,300 metamorphic events and places where we need a large amount of 541 00:27:42,300 --> 00:27:44,800 data to actually see Trends and minimal forecast area. 542 00:27:44,800 --> 00:27:47,600 So in particular had PhD students working in New Zealand 543 00:27:47,600 --> 00:27:50,900 to try and understand the Cretaceous metamorphic history 544 00:27:50,900 --> 00:27:54,500 of zealandia as it's breaking up from parts of gondwana and 545 00:27:54,500 --> 00:27:55,900 particularly in place. Like New Zealand. 546 00:27:55,900 --> 00:27:59,300 It's really challenging because there are older and younger 547 00:27:59,300 --> 00:28:00,900 faces. Have been a morphism that you 548 00:28:00,900 --> 00:28:03,700 might also have to contend with. And so that high spatial 549 00:28:03,700 --> 00:28:07,500 resolution technique is really useful for dick involving the 550 00:28:07,500 --> 00:28:10,000 different scales have been a morphism, the different imprints 551 00:28:10,000 --> 00:28:12,800 of metamorphism on those rocks. It's fantastic. 552 00:28:12,900 --> 00:28:15,400 Several people I've spoken to have said this is really 553 00:28:15,400 --> 00:28:17,200 creating a revolution in the field. 554 00:28:17,200 --> 00:28:20,000 I can imagine that all kinds of people would be falling over 555 00:28:20,000 --> 00:28:22,100 themselves, to be able to use your methods, are your 556 00:28:22,100 --> 00:28:24,100 instruments. I think we're really actually, 557 00:28:24,100 --> 00:28:27,100 only at the beginning of our Our thinking about how do you best 558 00:28:27,100 --> 00:28:30,000 take that information and how do you really get the most out of 559 00:28:30,000 --> 00:28:31,800 that, in terms of a geologic interpretation? 560 00:28:32,200 --> 00:28:34,300 That requires people who are interested in more the data 561 00:28:34,300 --> 00:28:37,000 science side of things as well as the isotope geochemistry is 562 00:28:37,000 --> 00:28:39,300 also metamorphic petrology. So for me that's the most 563 00:28:39,300 --> 00:28:41,000 exciting thing is. I think we've got more people 564 00:28:41,000 --> 00:28:43,800 involved in the chronology Community to bring their 565 00:28:43,800 --> 00:28:47,000 expertise to these problems. John cockerill. 566 00:28:47,000 --> 00:28:49,100 Thank you very much. Thank you very much. 567 00:28:49,100 --> 00:28:53,100 It's been a real pleasure. For more about geology b, as 568 00:28:53,100 --> 00:28:56,200 well as pictures and illustrations, that support this 569 00:28:56,200 --> 00:28:58,900 podcast, go to geology B.com.