Metamorphic Rocks

"Rapid burial beneath many kilometers of sediment produces instantaneous pressure increases, but once again it takes too much time to heat the sediment.  In fact it would take many millions of years to heat up sediment buried 20 kilometers beneath the surface." — Kurt Wise, First International Conference on Creationism, 1986¹

"This research is acknowledged without implying that Professor Stanton would support the creationist conclusions—he would not." — Andrew Snelling, on the geologist whose work his model rests on, 1994²

"Short-duration regional metamorphism is a recently observed and poorly understood phenomenon in metamorphic geology.  In this review, it is defined as metamorphism on time scales that limit length scales (of the associated thermal anomaly) to significantly less than the thickness of the orogenic crust (<10 myr) or subducted oceanic lithosphere (<5 myr)." — Daniel Viete and Gordon Lister, Journal of the Geological Society, 2017³

Summary

A regional metamorphic rock is a sediment that was buried, heated to 500 to 700 °C, held there long enough for its minerals to re-form, and then brought back to the surface.  This article asks how long each of those steps takes, and whether a Flood year can hold them.  Its sibling on granite cooling handles the plutons;  this one handles the rock around and beneath them.

Nine findings, stated first.

1. The young-earth movement's own best geologist stated the problem correctly in 1986, and it has not been answered since. Kurt Wise told the first International Conference on Creationism that the reaction is not the issue: "any reaction which involves more than about 300 degrees Centigrade can be reproduced in the course of a single day or less." The heat is: "it would take many millions of years to heat up sediment buried 20 kilometers beneath the surface."¹ Andrew Snelling's founding paper eight years later concedes the same thing: "the biggest problem creationists face with the conventional scenario for regional metamorphism is the heat presumed to have been involved."²
2. The conduction floor is a two-input number. Heat crosses a thickness L of rock in a time of about L²/κ, where κ, the thermal diffusivity of rock, is about 10⁻⁶ m²/s.⁴ For 20 km that is 12.7 million years; the most generous bound, the slowest decaying mode of a slab heated from below, is 1.3 million years. In one year heat conducts about 11 metres into rock. In the 16 days Snelling allows Cooma, about 2.4 metres.⁵
3. The energy has to come from somewhere, and every route has now been priced. Heating the Barrovian type area of Scotland by 500 °C costs about 1.2 × 10²² J, for scale. Delivered in a year, that is 2 × 10⁵ W per square metre, about 160 times the sunlight reaching the top of the atmosphere, sustained for twelve months over 1,800 km². Carrying it in by hot water needs about 1.5 darcies of permeability through 15 km of crust; the measured mean at that depth is a million times lower, and the highest transient values ever inferred are still 2,800 times lower.⁶ Carrying it in by friction on a fault needs about 70 km of slip in a year and then leaves the heat on the fault plane. Accelerated decay hands the whole bill to the heat problem.
4. The "rapid metamorphism" results the young-earth side cites are real, and every one of them nests a fast event inside a slow history. Camacho and colleagues, the paper behind Snelling's 2006 article, report fluid pulses "as short as 10 years" inside metamorphic events of "approximately 20 kyr" inside an orogenic cycle of "less than 13 Myr."⁷ Ague and Baxter find the thermal peak in Barrow's own zones "lasted for only 200–300 kyr" inside an orogeny of 10 to 15 million years.⁸ Oliver and colleagues, in a paper titled "Fast tectonometamorphism," report that "the entire Grampian episode lasted 15 ± 2.5 m.y."⁹ The field's own definition of short-duration regional metamorphism is under ten million years.³
5. Snelling's one number, 12 to 20 days for the Cooma complex, contains no thermal calculation. It is 6 to 10 days for the neighbouring batholith, taken from his own radiohalo papers, plus another 6 to 10 days for the central granodiorite.¹⁰ His argument that the complex is an aureole around the batholith is contradicted by the paper he cites for the cooling history, which finds the cooling "more consistent with the unroofing of a regional thermal high than cooling of an igneous intrusion."¹¹ And Cooma, at 3.5 to 4 kbar, is the shallowest test case available; Barrow's sillimanite zone is 6 kbar and the Franciscan eclogites are 14 to 18 kbar.
6. The pressures are checkable by a second, physically unrelated method, and it agrees. Quartz-in-garnet elastic barometry reads the pressure locked on a quartz grain by the garnet that grew around it, with no chemical-equilibrium assumption. It gives 1.4 to 1.8 GPa for northern Franciscan eclogites, in agreement with the chemical barometers.¹²
7. Where the young-earth side has a point, it is granted here. The mainstream conductive model does not work for short orogens: Ryan and Dewey say so in a 2019 review,⁴ and Baxter, Ague and DePaolo found that Barrow's zones reached peak temperature within 2.8 ± 3.7 million years of one another, which "requires an additional source of heat beyond thermal relaxation."¹³ Tectonic overpressure is measured and real: Luisier and colleagues found two rocks in contact in the Alps recording pressures 0.8 ± 0.3 GPa apart.¹⁴ Garnet growth is measurably pulsed.¹⁵ None of these touches the temperature, and both ends of the mainstream heat dispute are five to seven orders of magnitude from a Flood year.
8. The young-earth camp does not agree with itself. Austin and Baumgardner need deep, fast burial; Oard needs no deep burial at all; Snelling needs shallow burial, moderate temperatures and hot water; Gentry needed the granites to be created rocks, and Snelling rejects him on field evidence.¹⁰ No published young-earth temperature estimate exists for any metamorphic rock.
9. Nothing new has been published on the young-earth side since 2008. The 2023 ICC radiohalo survey restates the Cooma result by citation and concedes the heat objection without a calculation.¹⁶

Verdict.  Metamorphic reactions are fast, and the young-earth literature is right to say so.  Heating kilometres of rock is not.  Conduction, hot water, friction and accelerated decay have each been priced here, and each misses a Flood year by three to seven orders of magnitude.  The mainstream's fastest measured durations are 10⁵ to 10⁷ years, and they sit inside longer histories.  Kurt Wise stated this in 1986;  forty years on, the movement has answered the pressure question with Stanton's precursor idea and left the heat question where he put it.

Part 1: What a metamorphic rock records

There are two kinds.  Contact metamorphism is the baking of rock next to an intrusion;  it involves heat and little extra pressure, and it reaches a kilometre or two from the contact.  Regional metamorphism covers hundreds to thousands of square kilometres, involves high pressure as well as high temperature, and is read as the record of deep burial in a mountain belt.  Wise's 1986 paper makes the same distinction and says the objections to creationism come from the regional kind.¹

Across the Scottish Highlands the regional rocks are arranged in zones named for the first appearance of an index mineral:  chlorite, biotite, garnet, staurolite, kyanite, sillimanite.  These are Barrow's zones, and the sequence is called Barrovian wherever it recurs.  Snelling's founding paper states the mainstream reading of them fairly:  the classical model "presupposes elevated temperatures and pressures due to deep burial and deformation/tectonic forces over large areas over millions of years."²

Temperature and pressure are read from mineral chemistry, and the calibrations are experimental.  Coexisting minerals exchange elements in proportions that depend on temperature, and certain reactions run only above a pressure that depends on temperature;  both are measured in the laboratory and inverted for the rock.  For Barrow's own zones, Ague and Baxter use peak temperatures of 535 °C in the garnet zone, 595 °C in the staurolite zone and 660 °C in the sillimanite zone, at 0.4 GPa for the first two and 0.57 GPa for the third.⁸  At Glen Clova, Barrow's sillimanite locality, the rocks "underwent peak metamorphism at c. 660 °C and c. 6 kbar."¹³  Under 2,700 kg/m³ of rock, 1 kbar is about 3.8 km, so 6 kbar is about 22 km of burial.

The young-earth authors report the same kind of numbers for their own field areas and do not dispute them.  Snelling quotes the New England conditions Davis Young put to creationists, "temperatures approaching 600°C and pressures of 5 kilobars," implying "a load of rock 16-19 kilometres thick."²  For Koongarra, his own doctoral ground, he reports amphibolite-grade metamorphism "estimated to represent conditions of 5–8 kb and 550–630 °C."¹⁷  For Cooma he writes that producing the migmatites "would have required temperatures of approximately 700 °C at pressures of 3.5–4.0 kbar."¹⁰  John Baumgardner puts Franciscan blueschist at "pressures of about 0.6-0.7 GPa," which "corresponds to depths of about 20 to 30 km in a subduction zone."¹⁸

The uncertainties on a pressure are tenths of a gigapascal, not factors of ten.  Luisier and colleagues list them for the Monte Rosa metagranite:  ±0.05 GPa from the experimental position of the albite = jadeite + quartz reaction, ±0.03 GPa from the silicon-in-phengite barometer, and ±0.2 GPa from the choice of thermodynamic database.¹⁴  And there is now a barometer that shares none of those assumptions.  Quartz-in-garnet elastic barometry measures, by Raman spectroscopy, the residual pressure that a garnet still exerts on a quartz grain it enclosed as it grew, and inverts the elastic equations of state.  Cisneros and colleagues applied it to the Franciscan Complex of California and found "pressures from northern Franciscan eclogites range from ∼1.4–1.8 GPa, at an estimated temperature of 500 °C," with different blocks agreeing to within 0.1 GPa.¹²  That is about 50 to 70 km of burial in a subduction zone that never got hot, and it matches the chemical barometers.  An objection that the pressures are an artefact of chemical-equilibrium assumptions has to explain why a method with no such assumption gives the same answer.

Time is read four ways.  Garnet can be dated directly by samarium-neodymium or lutetium-hafnium, and a large garnet can be drilled in concentric shells and each shell dated separately.¹⁵  Monazite and zircon grow new rims during metamorphism, and the rims are dated by uranium-lead.¹¹  Minerals that lose argon above a known temperature record when the rock cooled through it.  And diffusion geospeedometry uses the fact that a sharp chemical step inside a crystal smooths at a laboratory-measured rate;  a step that survives caps how long the rock sat hot.⁸  The first three depend on decay constants;  the fourth does not.  Part 4 shows what each gives.

Part 2: The young-earth models, in their own words

The positions are stated here before they are priced, each from its primary source.

Wise, 1986.  The first ICC paper on rock formation separates the two questions that every later paper runs together.  On the reaction:  "It seems that any metamorphic reaction can be reproduced in the lab.  Each of these reactions can be made to occur in less than a few weeks. … Chemical equilibrium in the process of metamorphism is thus rather quickly reached once the thermal conditions are achieved.  It is, however, rather difficult to achieve those conditions."¹  On the heat, the passage quoted at the head of this article:  burial can be fast, but "it would take many millions of years to heat up sediment buried 20 kilometers beneath the surface."¹  He applies the same arithmetic to contact metamorphism at Marysville, Montana, where a granodiorite a kilometre in radius sits inside a kilometre-wide aureole:  "the pluton should have taken something like 10,000 years to cool, and the sediments should have taken something like 10,000 years to heat up in order to undergo metamorphism."¹

Snelling, 1994, the precursor model.  Snelling's Creation Ex Nihilo Technical Journal paper answers Wise by borrowing from Richard Stanton of the University of New England, who had found the full range of index minerals within centimetres of one another in stratiform ore bodies and argued that the minerals track the composition of the original sediment rather than its depth.  Snelling's thesis is that "composition is the primary factor in metamorphism," so that "only moderate temperatures may be needed to transform the precursors into the index minerals of the zones of regional metamorphism, and such moderate temperatures would have conceivably been generated in the short time-scale in the Flood event."²  Two things about the paper are unusual and creditable.  It states the obligation it is answering in full, quoting Davis Young's demand that Flood geologists explain "how it would have been possible in less than one year" for the New England sediments to be deposited, buried 16 to 19 km, heated to 600 °C, uplifted and eroded.²  And it closes by conceding the work is not done:  "there is still a lot of work for creationists to do in dealing with many of the mineralogical and textural issues in metamorphic petrology from the short time-scale perspective, including conventional experimental studies on mineral stabilities and reactions."²  No temperature, depth, duration or heat flow is computed anywhere in its 24 pages.  "Moderate" is never given a number.

Snelling, 1994, the garnets.  The companion ICC paper is the one piece of original measurement in the young-earth metamorphism literature.  Snelling microprobed 33 garnets from Koongarra schists and found their compositions scattered across the zone boundaries of a 1960s classification scheme.  His conclusion is framed as a possibility:  "Creationists may thus be able to explain regional metamorphism within their time framework on the basis of catastrophic sedimentation, deep burial and rapid deformation/tectonics, with accompanying low to moderate temperatures and pressures."¹⁷  The paper reproduces, without dispute, the published conditions for his own rocks, 5 to 8 kbar and 550 to 630 °C.¹⁷  It does not compute what temperature the garnets did form at.  The instrument that gave the compositions is the instrument that gives the temperature, and the thermometer was not run.

Catastrophic plate tectonics, 1994 and after.  The CPT paper of Austin, Baumgardner, Humphreys, Snelling, Vardiman and Wise does not model metamorphism.  Under its predictions it says Flood models "claim that it is possible on a short timescale to explain … regional metamorphism (see, for example, Snelling)," citing the two 1994 papers above.¹⁹  Baumgardner's later 101 Questions treats the Franciscan blueschists of California as support for CPT, on the ground that they must return to the surface quickly to survive:  "This difficulty, of course, disappears in the CPT framework because the subduction and exhumation velocities are orders of magnitude higher and the time scale is orders of magnitude shorter."¹⁸  That is a claim about exhumation speed, not about heating;  the catastrophic plate tectonics article prices it.

Snelling, 2006, eclogite by hot water.  An ICR Acts & Facts piece reports Camacho and colleagues' Nature paper on the Bergen Arcs of Norway, where granulite was turned to eclogite along shear zones by hot fluid while lenses a few centimetres away never exceeded 400 °C.  Snelling reports the mainstream numbers accurately, including "the total heating duration must have been around only 18,000 years" and fluid events that "had to have lasted just ten years or less,"²⁰ then adds polonium-210 radiohalos from one eclogite sample and concludes "perhaps to only a few weeks or months!"²⁰  He does not report the outermost number in Camacho's abstract, the orogenic cycle of up to 13 million years;  Part 4 does.

Snelling, 2008, twelve to twenty days.  The ICC paper on the Cooma complex of New South Wales is the only place a young-earth author puts a number on a regional metamorphic terrane.  Its abstract:  "generation of the regional metamorphic complex only required 12–20 days, based on the catastrophic granite formation of the adjacent Murrumbidgee Batholith whose heat and hydrothermal fluids generated the regional metamorphic zones of the complex."¹⁰  Part 5 takes the paper apart.

Oard, 2015, tectonic overpressure.  Michael Oard's Journal of Creation note takes a different route:  if directed stress rather than the weight of overlying rock drove the reactions, then a pressure is not a depth.  "In the CPT model, plate movements of metres per second have the capability to create greater tectonic pressure at shallow depths and provide a better explanation of zones of UHPm. … As a result we are in a better position to explain how UHPm formed, possibly at depths shallower than 50 km."²¹  He also gives a rule that cuts both ways:  "we need to be skeptical of models claiming to demonstrate a past event.  Models are marginally useful for many reasons and are only as good as their input parameters and assumptions."²¹

Snelling, 2023.  The most recent statement, an ICC survey of radiohalos in 147 granites and metamorphic rocks, restates the Cooma result by citation and adds no timescale.  It does state the heat objection to its own mechanism:  "Hundreds of millions of years' worth of ²³⁸U decay must have occurred within days … One major objection raised is the huge amount of heat (as well as radiation) that would seem to be generated by the pulse of accelerated ²³⁸U decay."¹⁶  The answer offered is that the halos survived, not a calculation.

A search of all nine ICC proceedings for metamorphism, metamorphic rocks, eclogite and blueschist returns Wise 1986, Tyler 1990, the two Snelling 1994 papers, Snelling 2008 and the 2023 survey.  There is no ICC paper on regional metamorphism after 2008.

Part 3: The arithmetic of heat

Every number in this part is either quoted with its source or computed in a short script kept beside the article, with every input named.⁵  Rock volumes that no model states are labelled scale only;  the conclusions do not depend on them.

Conduction

Heat moves through rock by conduction at a rate set by one material constant, the thermal diffusivity κ, about 10⁻⁶ m²/s for crustal rock.  The time for a thermal disturbance to cross a distance L is about L²/κ.  Ryan and Dewey give the relation as England and Thompson's equation 10 and work an example:  "the thermal anomaly associated with delamination of the asthenospheric mantle underlying a crust thickened to 60 km would take about 28.5 my to propagate upwards 30 km."⁴  Turcotte and Schubert's textbook gives the same estimate for magma bodies.²²  It is not a model;  it is the definition of diffusivity applied to a length.

The second column is the honest generous bound:  the e-folding time of the slowest-decaying temperature mode in a slab of thickness L held at fixed temperatures top and bottom.  Even that gives over a million years for the 20 km Wise named.  The same constant answers the question the other way round:  how far does heat get in the time available?  The penetration distance is about 2√(κt).  In one year, 11 metres.  In sixteen days, 2.4 metres.  In a thousand years, 355 metres.  A pile of Flood sediment 20 km thick, buried in a year, is warmed by conduction over its bottom eleven metres.

Radioactivity inside the sediment does not help.  Ryan and Dewey compute that the measured potassium, uranium and thorium of the Dalradian would have raised its temperature "by 17.5 - 30.0 °K.my⁻¹," so that a pile starting at 150 °C "would have only reached 290 – 390 °C after 8 my."⁴  In a year that is twenty millionths of a degree.

The energy bill

Whatever carries the heat, the amount is fixed by the rock.  Heating a mass m of rock by ΔT costs m × 1,000 J/(kg·K) × ΔT.  For scale, take the Barrovian type area of the northeast Highlands as 60 by 30 km, and take 5 km of rock heated by 500 K;  no published model gives these figures and the result scales linearly with each.

For comparison, the mean geothermal flux through the continents is under a tenth of a watt per square metre, and the sunlight reaching the top of the atmosphere is 1,361 W/m².  The Barrovian case needs about 160 suns over 1,800 km² for a year.  The Cooma case, on Snelling's own outcrop area of "exceeding 300 km²,"¹⁰ needs about 4,700 suns for sixteen days.  Shortening the time makes the power problem worse, and Snelling's is the shortest claim in the literature.  Dehydrating the sediment adds to the bill:  Connolly and Thompson give the enthalpy of dehydration as 3.35 to 4.2 kJ per gram of water,²³ and an unmetamorphosed pelite carries about 4 per cent water by weight,²³ which is another 27 to 34 per cent on top of the sensible heat.  Over millions of years they find that cost "only marginally significant";²³ in a year nothing is marginal.

Route by water

Snelling's mechanism is hot water from a batholith.  Water is a good carrier, so price it.  Delivering 1.2 × 10²² J with water that cools by 200 K takes 1.45 × 10¹⁶ kg, about 14,500 km³, more than the volume of the rock being heated, through the terrane in a year.  Spread over the 1,800 km² footprint that is a Darcy flux of 2.5 × 10⁻⁴ m/s.  Drive it with the largest sustained pressure gradient the crust offers, lithostatic minus hydrostatic, about 17 kPa per metre, at a viscosity of 10⁻⁴ Pa·s for hot water, and Darcy's law asks for a permeability of 1.5 × 10⁻¹² m², about 1.5 darcies, through the whole thickness.

The measured crust is nowhere near that at depth.  Ingebritsen and Manning's compilation of geothermal and metamorphic data finds that "mean permeability (k) of tectonically active continental crust decreases with depth (z) according to log k ≈ −14 − 3.2 log z, where k is in m² and z in km."⁶  At 15 km that is 1.7 × 10⁻¹⁸ m², nine hundred thousand times too low.  They also fit the highest transient values ever inferred, from earthquake swarms and reaction fronts, as "log k ≈ −11.5 − 3.2 log z";⁶ at 15 km that is 5.5 × 10⁻¹⁶ m², still 2,800 times too low.  The granite cooling article reaches the same wall from the other side:  a batholith that sheds its heat in a year needs 28 to 70 darcies, against a measured granite maximum of 0.1 darcy.  The water that is to heat the terrane has first to leave the pluton, and the same rock stands in its way in both directions.

Route by friction

Shear heating on faults is the other advected source the mainstream discusses.  It is bounded by rock strength.  Take a shear stress of 100 MPa, the order of the frictional strength of a crustal fault and used here for scale only.  Depositing 1.2 × 10²² J on a single fault plane under the 1,800 km² footprint then needs about 68 km of slip in the year, and the heat lands on the plane, from which conduction carries it eleven metres.  At an implausible 1 GPa it is still 7 km of slip.  No young-earth paper proposes this route;  it is priced here so that it is not left open.

Route by accelerated decay

The only remaining young-earth heat source is the RATE project's accelerated nuclear decay, which Snelling invokes for Cooma's cooling curve.¹⁰  Its global budget is audited in the heat problem and RATE's helium diffusion and is not re-argued here.  For a metamorphic pile the sum is short.  Ryan and Dewey's rate for the Dalradian's own potassium, uranium and thorium is 17.5 to 30 K per million years of ordinary decay.  Snelling's requirement is "hundreds of millions of years' worth" of decay within days.¹⁶  One hundred million years' worth, deposited in the pile before any of it can escape, is 1,750 to 3,000 K;  two hundred million is 3,500 to 6,000 K.  That does not metamorphose a sediment, it melts or boils it, and it does so wherever the uranium is rather than in the temperature zones Barrow mapped.

Contact metamorphism

Wise's Marysville figures reproduce.  For a 1 km aureole the conduction table gives 3,200 to 32,000 years, and Jaeger's classical solution puts complete solidification of a granite sheet 2 km thick at 0.016 × 2000² = 64,000 years.²⁴  A contact aureole is the fastest metamorphism that heat conduction allows, and it takes thousands of years around a small pluton.  The sibling article gives the full treatment for batholiths.

Part 4: What "rapid" means in the mainstream literature

The young-earth side is right that the mainstream has found regional metamorphism to be much faster than the classical model predicted.  The question is what the numbers are, and the answer in every case is the same shape:  a fast event nested inside a slow history.

Camacho and colleagues is the paper Snelling built his 2006 article on, and its abstract states all three numbers in one sentence:  "we use ⁴⁰Ar-³⁹Ar data coupled with a thermal model to constrain the time-integrated duration of an orogenic cycle (the burial and exhumation of a particular segment of the crust) to be less than 13 Myr.  We also determine the total duration of associated metamorphic events to be approximately 20 kyr, and of individual heat pulses experienced by the rocks to be as short as 10 years."⁷  The ten years is the duration of a pulse of hot water through a fracture.  The burial to 60 km and the return are the 13 million.  Snelling quotes the innermost number as the timescale of eclogite metamorphism;  it is the timescale of one heating event within it.  The result was also disputed in Nature the following year by Bjørnerud and Austrheim, who had studied the same rocks and were "sceptical of the assertion by Camacho et al. that eclogite temperatures were reached only in the vicinity of fluid-filled fractures."⁷  No creationist source cites the reply.

Ague and Baxter is the paper the young-earth side should be citing and mostly is not.  It measured strontium diffusion profiles in apatite and multi-element profiles in garnet from Barrow's garnet, staurolite and sillimanite zones and found "the thermal peak was extremely brief and lasted a few hundred thousand years.  This timescale is one to two orders of magnitude shorter than peak timescales predicted by conventional models based on conductive relaxation of overthickened crust."⁸  The authors attribute the heat to magma and fluid, which is Snelling's mechanism.  But the same paper holds the outer clock:  "While a background (i.e., < ∼500 °C) regional conductive heating and cooling due to overthickening probably spanned nearly the entire 10–15 Ma orogeny, the thermal peak conditions lasted for only 200–300 kyr."⁸  Two hundred thousand years is the innermost number, and it is two hundred thousand Flood years.

Oliver and colleagues put the word "fast" in a title and defined it:  "the entire Grampian episode lasted 15 ± 2.5 m.y. and … it took fewer than 7.6 m.y. to expose high-grade rocks following the peak of metamorphism."⁹  The paper also carries a check no Flood model has addressed:  garnet eroded off the rising mountains and redeposited in the Midland Valley dates at 465 ± 2.5 Ma, two million years after the 467 ± 2.5 Ma metamorphic peak.  A Flood year would have to grow the garnet at 20 km, exhume it, erode it and bury it in a basin, and then explain why two clocks on the same mineral differ by the two million years the slow model predicts.

Viete and Lister wrote the review that defines the term.  Short-duration regional metamorphism is "metamorphism on time scales that limit length scales (of the associated thermal anomaly) to significantly less than the thickness of the orogenic crust (<10 myr) or subducted oceanic lithosphere (<5 myr)."³  They add that "diffusion geospeedometry typically yields extremely short metamorphic durations (<1 myr)," and that benchmarking those results against high-precision dating "must become a priority."³  So the shortest class of mainstream result, the sub-million-year one, is the class the field itself flags as unconfirmed;  and it is still a million years.

One more point about the table.  The innermost numbers and the outermost numbers come from the same physics.  Camacho's ten years and thirteen million years are one argon dataset and one thermal model.  Ague and Baxter's 200,000 years comes from diffusion coefficients measured in the laboratory, and the 10 to 15 million from radiometric ages.  A reader who accepts the fast number as a measurement has accepted the method that gives the slow one.

Part 5: Cooma, the one young-earth number

The Cooma complex is a set of concentric metamorphic zones, biotite outward through andalusite and K-feldspar to a migmatite zone, with a small granodiorite at the centre and the Murrumbidgee Batholith beside it.  Snelling collected seven samples across the zones, counted radiohalos in their biotite, and found polonium halos most abundant in the high-grade zone and the granodiorite.  He reads that as hydrothermal fluid from the cooling granite, and therefore as a fluid-flow aureole rather than a burial sequence.

The number then follows in two sentences, and neither is a thermal calculation.  "Based on the catastrophic rate for granite formation of 6–10 days (Snelling, 2006b, 2008a), this regional metamorphic complex would thus have been produced during this same timescale of 6–10 days over which the granite batholith was emplaced and cooled."¹⁰  Then the granodiorite's own 6 to 10 days is added, "so the total timescale for the formation of this regional metamorphic complex with its central granodiorite would have been on the order of 12–20 days."¹⁰  The 6 to 10 days is not derived in this paper.  It comes from Snelling's granite papers, where it rests on polonium-210's 138-day half-life and the assumption that the halos formed as the rock cooled;  the polonium radiohalos article shows that chain also requires accelerated decay and leaves Snelling's own supply-rate objection unanswered.  Every link except the half-life is a claim from another Snelling paper, and the 2008 paper is then offered as confirmation of the model it assumes.

Three further problems, each from Snelling's own sources.

His key source says it is not an aureole.  Snelling's argument needs the complex to be a regional aureole around the batholith, so that the granite's timescale is the metamorphism's.  He cites Ian Williams' 2001 study of Cooma's zircon and monazite repeatedly, for the detrital ages and for the cooling curve.  Williams' abstract concludes that "Cooling of the metamorphic complex was relatively slow (average ∼12°C/10⁶y from ∼730 to ∼170°C), more consistent with the unroofing of a regional thermal high than cooling of an igneous intrusion."¹¹  The rock cooled by being uncovered, not because a pluton next to it went cold.  Snelling does not engage the sentence.

Four clocks give the cooling in the right order.  Snelling reports the mainstream cooling history himself:  built from U-Pb, Rb-Sr, K-Ar and Ar-Ar ages with their different closure temperatures, "the granodiorite and metamorphic complex supposedly took 45 million years to cool from 735 to 150 °C."¹⁰  A body that cooled in days gives every system the same date.  His answer is accelerated decay, which has to explain why the order survives, and which is the heat problem again.

It is the easiest case, and it is a contact claim.  Cooma is low-pressure, high-temperature:  700 °C at 3.5 to 4 kbar, about 13 to 15 km.  Barrow's sillimanite zone is 6 kbar;  Baumgardner's own Franciscan is 20 to 30 km;  the Franciscan eclogites are about 50 to 70 km.  The young-earth literature has never attempted the harder cases.  And a metamorphic aureole around a batholith is contact metamorphism by another name;  the claim that it formed in 12 to 20 days is answered by the aureole arithmetic of Part 3, which gives thousands of years for a kilometre, and by the batholith's own cooling, which the sibling article puts at 10⁴ to 10⁷ years.

Part 6: Where the young-earth side has a point

Four things are granted in full.

The classical conductive model does not work everywhere.  England and Thompson's 1984 model, as Ryan and Dewey restate it, needs "a period of 20 my for thermal relaxation after shortening and before the onset of uplift and erosion," and they call that requirement "perhaps the greatest difficulty for the general applicability" of the model.⁴  Their abstract is blunter:  conductive models "will not produce the observed Barrovian (medium temperature, medium pressure) assemblages within some short-lived orogens."⁴  Viete and Lister say that "without appealing to exceptional heat sources, thermal models have been unable to account for peak metamorphic temperature during collisional orogenesis and subduction."³  Baxter, Ague and DePaolo found that the near-simultaneous peak in three of Barrow's zones "requires an additional source of heat beyond thermal relaxation of a variably over-thickened crust," and proposed "local igneous intrusions, with synmetamorphic ages."¹³  Snelling's magma-and-water mechanism is a live mainstream option.  The dispute is between conduction over twenty million years and advection over a few hundred thousand.

Tectonic overpressure is real.  Luisier and colleagues measured it:  a whiteschist body and the metagranite enclosing it, which "were always at the same depth during the Alpine orogeny," record peak pressures 0.8 ± 0.3 GPa apart.¹⁴  Oard is not misrepresenting this literature.  Its limits are that the effect needs a weak body inside a strong one and so predicts differences between neighbours rather than a uniform error across a terrane;  that 0.8 GPa is measured at ultrahigh-pressure conditions, not at the 0.4 to 0.6 GPa of a Barrovian terrane where the available differential stress is a modest fraction of the load;  and that it changes no temperature.

Garnet growth is pulsed.  Dragovic and colleagues drilled zoned garnets from Sifnos and found "a >2 order of magnitude acceleration in volumetric growth rate from crystal core to rim, with the final growth pulse occurring rapidly (<0.8 My), during a period of nearly isobaric heating at >75 °C/My."¹⁵  Metamorphism happens in bursts.  The bursts are hundreds of thousands of years long, and 75 °C per million years is the fastest measured heating rate in the dossier;  a Flood year needs about seven million times that.

The reactions are fast.  Wise said it first and the mainstream agrees.  The disagreement was never about the reaction.

Objections and responses

"Metamorphic reactions run in days in the laboratory, so metamorphism is fast."  Granted, and stated by Wise in 1986.  The laboratory supplies the temperature by a furnace.  The question is how twenty kilometres of rock reach 600 °C, and the furnace for that is conduction at 10⁻⁶ m²/s, hot water through rock of 10⁻¹⁸ m² permeability, or friction.  Part 3 prices each.

"The mainstream now admits rapid regional metamorphism."  It does, and it has defined the word.  Rapid means under ten million years;  the sub-million-year class comes from geospeedometry that the same review says needs benchmarking.  A creationist who cites Ague and Baxter's 200,000 years, or Camacho's ten-year fluid pulses, is citing a paper whose outer clock reads 10 to 15 million years in the one case and up to 13 million in the other.

"The heat came by hydrothermal fluid, not conduction."  Then the fluid had to get in.  Part 3 computes the water:  14,500 km³ through 1,800 km² in a year, needing about 1.5 darcies through 15 km of crust, against a measured mean of 1.7 × 10⁻¹⁸ m² and a transient ceiling of 5.5 × 10⁻¹⁶ m².  The same water first had to leave a batholith whose own permeability tops out at 0.1 darcy.  A solution would have to show a mechanism that opens the middle crust by a factor of a thousand to a million and keeps it open for a year.

"Tectonic overpressure means the rocks were never that deep."  Partly granted.  It cuts an inferred depth by at most a factor of two at ultrahigh pressure, by much less at Barrovian pressure, and it cuts no temperature.  A rock that records 600 °C still had to be heated to 600 °C, and that is where the year is spent.

"The index minerals record the composition of the original sediment, not depth."  This is Stanton's precursor principle and Snelling's whole 1994 case.  Stanton himself did not draw the creationist conclusion, as Snelling records.²  Three answers.  A garnet that grew from a chlorite precursor still had to reach the temperature at which garnet, not chlorite, is stable;  which garnet forms does not decide whether garnet forms.  The composition-versus-grade scheme Snelling argued against is a 1960s plot that modern thermobarometry does not use;  the exchange thermometers and net-transfer barometers are calibrated on coexisting phases, and an independent elastic barometer agrees with them.  And the precursor model makes a prediction nobody has tested:  that isograds should not follow independent thermometers such as the Raman spectrum of carbonaceous material.  Snelling had the microprobe and did not run the thermometer.  Thirty-two years later no young-earth temperature for any metamorphic rock exists.

"Accelerated decay supplied the heat."  That is a heat source of about 10²⁹ J, audited in the heat problem.  For this article it fails on a narrower point:  it heats rock uniformly by its uranium content, so it cannot draw zones, and it cannot explain why Cooma's four isotopic clocks read in closure-temperature order.

"All these durations assume constant decay rates."  The radiometric ones do.  Ague and Baxter's 200,000 years does not;  it comes from strontium diffusion in apatite and cation diffusion in garnet, with coefficients measured in the laboratory, and it is still 200,000 years.  Camacho's ten years comes from the same argon profiles as his thirteen million.  The fast results and the slow results are not separable.

"The Barrovian rock volume in Part 3 is invented."  It is, and it is labelled so.  Divide the volume by a hundred and the flux is still 1.6 suns for a year and the permeability requirement drops by a hundred, to 9,000 times the measured mean.  Use Snelling's own 300 km² and 16 days instead and every number gets worse.

"The conductive model has failed, so the mainstream has no model either."  Ryan and Dewey's conclusion is that no single heat source explains every Barrovian terrane, and that is reported here as an open problem.  But the dispute is between about 20 million years and about 200,000, and each side of it can be checked against clocks that read in order.  A Flood year is 10⁻⁵ of the short end.

Issues and unanswered questions

• England and Thompson 1984 was not read directly. The founding paper is behind an Oxford paywall that resisted every route tried; its equation and its 20-million-year relaxation are quoted here through Ryan and Dewey 2019 and Ague and Baxter 2007. Viete et al. 2011 is quoted the same way. Williams 2001 and Viete and Lister 2017 were read in abstract only; their full texts would let the article cite Cooma's cooling curve and the short-duration catalogue at page level.
• No young-earth temperature estimate exists to test. The precursor model would be settled by one traverse across one Barrovian isograd with an independent thermometer and a bulk-rock analysis on each sample. Nobody on that side has published it.
• The shear-heating bound is crude. It assumes one plane and a constant 100 MPa; a fault zone weakens as it heats, which makes the bound more generous than reality, not less. Viete's 2006 shear-heating model for the Barrovian was not obtained.
• The fluid calculation assumes bulk Darcy flow. Channelised flow through fractures can carry a higher local flux, but heating a whole terrane needs the whole terrane wetted, and the transient permeability fit used here is already the highest inferred anywhere. Whether catastrophic plate tectonics could generate crust-scale transient permeability has not been modelled by anyone.
• The Franciscan fossils and the blueschist exhumation argument are handled in the catastrophic plate tectonics article and its ultrahigh-pressure section, not here.
• The radiohalo counts at Cooma have no published mainstream reading. Water release rising with grade and falling in the melt zone is what any petrologist would expect, and it does not itself bear on duration; the polonium radiohalos article carries the physics.

Verdict

The young-earth literature on metamorphic rocks is right about one thing and has left the other where Kurt Wise put it in 1986.  Reactions are fast.  Heating kilometres of rock is not.  Conduction moves heat eleven metres in a year;  hot water needs a crust a million times more permeable than the one measured;  friction needs tens of kilometres of slip;  accelerated decay is the heat problem.  The one young-earth number, 12 to 20 days for Cooma, is two granite timescales added together with no heat transfer in the paper, and its own cited source says Cooma did not cool as an aureole.  The mainstream has a genuine dispute about whether the heat arrived by conduction over twenty million years or by magma and water over a few hundred thousand.  Both are measured, both sit inside longer histories, and both are more than a hundred thousand Flood years long.

Sources