i see youre in san diego, thats a bit far....... i was specific. im in the valley. the valley is a well known nickname for an area in AK. i would assume things are quite different here due to its rich prospecting history. id like any links that can be thrown my way , ...
It doesn't matter that Mark's not specifically in your area. His info is true of any state in the USA. You need to say what
type land WITHIN that area. Ie.: the land in the part of AK you speak of might be either a) city, b) county, c) state, d) federal, or e) private. And even within each of those public entities, is mutiple types of land that may differ as well. Ie.: not all city land is city PARK land (so ... meaning, if you found something dire in city parks code, it wouldn't necessarily mean other types city land, like road right-of-way, for instance, since that's not "park" land.
And as for links sent your way, be aware that there need not be any link sent to you saying metal detecting is allowed. There doesn't need to be express allowance for an activity, in order to do it. Example: you will probably not find "laws" that say you can fly frisbees, right? So actually, the ABSENCE of any mention of metal detectors, is actually a good thing. So the absence of "links" you can find, doesn't bode poorly for you, but in fact, bodes well. Because if something is not prohibited, well then presto, it's not prohibited.
And the presence of historical sites does not mean that "well there must be some sort of laws". Because think of it, don't you think that md'rs in all other states seek out old (aka historic) sites? I mean, how boring is it to hunt new sites afterall? And we hit old parks, schools, beaches, camps, etc.... all the time, so long as not specifically forbidden. Unless you're talking sacred sensitive monuments, well sure, use common sense. But run of mill old parks, foundations in the middle of nowhere, etc...? Not necessarily forbidden "just because they're old", unless you saw some specific wording saying such a thing.
So just figure out the entity of the land you have in mind (city, county, or state),and look to see if they have a website listing their municipal codes, laws, rules, etc... If you see no mention of "metal detectors" or "metal detecting", well, then there's your answer

If they don't have a website, you're welcome to go to city hall, and ask where the public can view the city codes, laws, etc... It has to be in writing somewhere, available for public viewing. Eg.: in binder form behind the front desk. Or at the public library, etc... Look it up for yourself, rather than thinking you need someone's "permission", lest you risk a whimsical arbitrary "no", where no such verbage really says such a thing.
But to be honest with you, most of us wouldn't even go that far. Most of us would see if something on the sign at the entrance forbids it, and if not..... well, you get the picture. And sure, don't be an eyesore raiding obviously sacred sites, making holes in manicured turf in front of bored landscapers, etc...