Neither chlorine-38 nor chlorine-39 are either calcium-40 or argon-40. Sort of like a duck is not a frog, and a persimmon not a paramecium. That, and 40+1-4 does not equal 38, so one argon-40 plus one proton minus one alpha particle ( the four) won't get you to anything-38.
So the only thing I can say, and it goes against conventional understanding, is that 40K/40Ar decay requires a neutron and the expulsion of a proton.
Radioactive decay is a spontaneous reaction. Decay does not require anything except the parent nuclei and the passage of time.
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"For a collision between argon 40 and a proton, the result would be emission of either two protons to get Cl-39 or an alpha particle to get Cl-38."
This would thus mean that, in the cases where the ages of crystals were determined with the K/Ar or Ar/Ar methods, those crystals are actually older than the ages determined by these methods. It would mean that those geologists underestimated the ages of those crystals.
I will explain why, quickly. For example, the K/Ar method starts working with the crystallisation of minerals.
Ar is an inert gas and can't be incorporated in the chemical reactions resulting in the crystal lattices of crystals. That's how we start, from basic chemistry. When the crystal forms, 0% Ar in the crystal lattices.
Then the K in those lattices start decaying according to basic physics.
The more the percentage of Ar in crystal lattices, the older the crystal. So, old OS is telling us that some Ar in the crystal lattices are removed via protons.
OS just confirmed that the earth is old. Very, very old.
On the magma level, it does look like 40K is being forced to turn into 40Ar and 40Ca by neutrons and protons.
Not even wrong.
Calcium is irrelevant to radiometric dating. As I posted before and you denied, 40K decays to 40 Ar by capturing an electron from an inner shell to turn a neutron into a proton and emitting a 1.460 MeV (minimum) gamma ray and a neutrino.
Luckily for humanity, both the K/Ar and Ar/Ar methods only start working after the magmatic phases.
What's your proof?
Pressie is merely calling your attention to a very well known fact, that some rocks contain minerals that take on the orientation of the existing magnetic field as they form. This can happen in volcanic rock, sedimentary rock, and metamorphic rock. The study of such rocks and their layers is called paleomagnetism. This field is how we know the position and orientations of ancient continents over past eons, as shown in videos like this: