So how did the GC get laid down from a mainstream POV? Deterministic models?

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From Tranquility Base:
Refs: The RATE book (see last link) has the diffusion calc in it (I've read it), the mainstream Gentry ref records evidence of vast excess helium in zircons, the web links contain mainstream refs to the helium budget problem, and I link to the RATE site where they report that the experimental helium diffusion rate backs up their previouls argon extrapolation:

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R.V. Gentry, G.L. Glish and E.H. McBay (1982) Geophys Res Lett 9:1129-1130
http://www.answersingenesis.org/docs/1401.asp#r7
http://www.answersingenesis.org/home/area/magazines/tj/docs/v8n2_helium.asp
http://www.icr.org/headlines/ratereport.html

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I'd like to address the helium retention in granite issue:For Creationists, this subject by itself should be enough to convince them of the untenability of YECreationism. A small dose of understanding, and a healthy skepticism of supposed "scientists" who intentionally mislead the lay public will awaken those who are willing to examine the facts objectively.TB's links are the usual data-free content paraded by YEC-mouthpieces (as Joe has complained about). It takes a little more digging to find actual numbers. Here's one bit I found:
Gentry's Helium stuffIt says, in part...
"we cite two interesting items of data from research Dr. Robert Gentry was involved in for the purpose of locating suitable sites for nuclear waste storage. A byproduct of his work was data that supports a recent creation.

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He was studying core sections taken at five different depths from about 3,000 to 15,000 feet during a drilling operation in granite{from a borehole in New Mexico}. He found that the temperature increased with depth--up to 313 C (595 F) at the deepest point......(stuff about lead retention deleted)... [i][b]Helium Absence [/i][/b]{this should read helium excess, of course...whf} [b][i]Indicates Youth[/b]Other experiments with these deep core well sections were run. This time, the amount of helium was measured. During the radiometric decay of uranium to lead, alpha particles are given off. These particles are helium nuclei. Helium, a gas, has been found to migrate out of various minerals, such as zircon, even at room temperature. Hence scientists have generally given up trying to use this system as an accurate radiometric age measurement, even on surface rocks.If the evolutionary suppositions were correct, it would be expected that because of the long earth history and the high temperatures of the deep core wells, that there would be very little or no helium left here. However, if the creation of the earth were recent (several thousand years ago), then measurable quantities of helium would be expected.Gentry’s data indicated amazingly high retention of helium even at 197 C (387 F).[/i]Unfortunately for the YEC case, this entire argument is based on a couple of glaring factual errors, with a few ridiculous assumptions thrown in to sweeten the pot. The result is a slick, plausible-sounding argument that does an excellent job of deluding those already inclined to accept mythology and fairy-tales as factually accurate (thus producing the desired effect - donations!), but is entirely divorced from reality.I'll bet you are just dying to learn about these factual errors and assumptions... yes?No 1.
Helium, a gas, has been found to migrate out of various minerals, such as zircon, even at room temperature. This is misleading to the point of falsehood. Helium does, in fact, migrate out of minerals - even at room temperature. But a few - [i][b]including zircon[/i][/b] - loose so little He at room temperature that they are effectively closed for the lifetime of the Earth (meaning far longer than billions of years). The closure temperature for zircon is 180-230 deg C. Apatite = 70 deg C, and titanite = about 200 deg C.The very next sentence is just plain dead wrong. Only colossal ignorance of geology or intentional deception can explain this:No 2.
Hence scientists have generally given up trying to use this system as an accurate radiometric age measurement, even on surface rocks.As of about 15 years ago this was correct. Then the high closure temperature of these 3 minerals was discovered. Since then, much work has been published using helium diffusion as a thermochronometer (quick tutorial). You can buy a thermal history reconstruction of a sample from many labs (Geotrack International). For a thorough treatise on the subject, read several geochemistry books before tackling this...He diffusion and (U-Th)/He thermochronometry of zircon: Initial results from Fish Canyon Tuff and Gold Butte, Nevada
Ignorance of this work would be appalling incompetence in a serious earth scientist who is interested in the age of the earth. Deliberately failing to mention it would be dishonest. Without more data, I cannot say which is true in this case, although I lean toward the incompetent explanation, given the track record of these "researchers".More subtle is the simplistic assumption built into Gentry's argument:No 3.
Erroneous assumption:
Creationists commonly misapply the principle of uniformitarianism. ASSUMING that the rock has ALWAYS been at 197 deg C is the mistake here. A good clue that this is a faulty assumption is found in the borehole temp vs depth data supplied in the figure above. The 197 deg temp is found at a depth of 3 km, when we would expect to find that temp at a depth of 5 or 6 km or more. Unless this is a cooling, recently emplaced pluton (it's not, it's a billion years old), such high temps define an area of high heat flow from below the surface - a hot spot - similar to the one under Hawaii. As we all know, hot spots move relative to the surface. The hot spot under New Mexico has left a trail of volcanoes through California, Arizona, New Mexico and western Texas.So the rocks in the borehole certainly cannot be assumed to have been at their current temps for a billion years - the hot spot hasn't been there very long in geological terms.One more fatal error remains in this argument. This one is a flaw of logic:No 4.
Under the YEC model favored by Tranquility Base, billions of years worth of helium were released in one massive pulse of radioactive decay only a few thousand years ago. Ignoring the fact that this would melt the entire earth, helium should still be found in ALL minerals of the Earth, regardless of temperature...
"if the creation of the earth were recent (several thousand years ago), then measurable quantities of helium would be expected. "
They would be expected in ALL minerals, not just the zircons, because the diffusion process is so slow. Even for the minerals with low closure temps, significant amounts of helium should still be present after only a few thousand years.The Creationist argument..."If the evolutionary suppositions were correct, it would be expected that because of the long earth history and the high temperatures of the deep core wells, that there would be very little or no helium left here. " ...applies equally well to ALL minerals. Since helium is, in fact, missing in ALMOST all minerals, we only need to explain why a very few minerals contain measureable helium. In the case of zircon, it retains its helium even at a range of temperatures in the neighborhood of 180-230 deg C. Recent heating of the site in New Mexico to slightly more than the closure temp has not finished driving out all the helium from the zircons yet.Far from being evidence for a young Earth, this issue actually presents compelling reasons why the Earth CANNOT be only a few thousand years old. There is no possible mechanism - other than ad hoc appeals to miracles - for removing helium so thouroughly from the vast majority of the minerals in the Earth's crust within the timeframe required by YEC mythology. But miracles are standard fare in mythology... just don't try to pass it off as science.

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Originally posted by Tranquility Base:
Even the mainstream view is that these formed via transgressions/regressions of sea onto land, not via river deltas etc.

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There are large amounts of fluvial deposits (river deltas, etc) forming VAST, FLAT LAYERS found in many area of N. America - like the Moenkoi Formation in this picture... "The Moenkoi Formation, which is about 1,800 ft at its thickest, is composed of fluvial (stream) deposits of silt, sand and mud in the east, which grade westwardly into marine limestone. In areas where large paleostreams can be reconstructed, they appear to have flowed to the west and to the north...Raindrop prints and salt casts are present on some bedding planes also (Chronic, 1990, p. 195). The bulk of the Moenkopi sediments appear to have been deposited by streams moving west-northwest from a cratonic area of low relief (Lemon, 1993, p. 324)."
(from Triassic Strata of the Colorado Plateau)Why are these strata so quickly dismissed from your consideration? Is is because your YEC framework is hopelessly inadequate to explain their presence and formation?

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These erosional and depositional feautres are superimposed on top of the vast beds generated via transgressions. I know that mainstream geolgoists know this but I sometimes think they fail to point out the qualitative differnece of the vast beds generated by transgressions to the Lyellian feautures that formed after each regression.

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This is pure fantasy on your part, TB. The VAST BEDS contain innumerable "Lyellian features" ... incised river channels, hogback ridges, deep and extensive weathering mantles, saprolites and laterites... the list is extensive... all within and part of each VAST, FLAT LAYER.

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I very much understand the gravitational reason why sediments are flat. However, IMO we should only expect them to be very flat when they are rapidly laid down. Normal continental shelf floors are not flat like the Grand Canyon marine strata! I've scuba dived - I know and I can also look at Grand Canyon sections (or the road cuttings near my house) for a comparison.

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Now you are becoming nearly incomprehensible. You say continental shelfs are NOT FLAT?????
What is you definition of flatness?
Using any measure I can think of, the continental shelf is about the second flattest area on the planet. Only the abyssal plain is flatter. Layers of sediment are being deposited today on continental shelfs that extend unbroken for thousands of miles laterally and tens to hundreds of miles offshore. All flatter'n a pancake.What you see while scuba diving on a reef should be compared to reef analogs found on land... like El Capitan in New Mexico. There are numerous other reef structures in the West you could look at. Some form VAST, FLAT BEDS by the widespread accumulation over a large area of small reef structures, sort of like the Great Barrier Reef in Australia. Try to think in the dimension of time as well as space when dealing with geology. Imagine what the Great Barrier Reef would look like if sea-levels slowly rose or fell a few hundred meters...
Since the continental shelf is SO FLAT, such a change in sea level will move the coastline hundreds of km. If the reef-building continued along the way as the coastline moved, the Great Barrier Reef would become a VAST, FLAT BED of limestone composed of a succession of overlapping reef structures.In fact, there are really HUGE layers in N. America composed entirely of the broken fragments of crinoids - a dominate reef building animal in the past.Have you had any luck extracting actual data on helium diffusion from the RATE book? All the links you have provided so far have been consistently content-free as far as numbers, examples, samples and such. Is the basic contradiction contained in this YEC argument beginning to sink in yet?