While Tom is correct in saying it doesn't say anything about metal detecting, I would be prepared to be confronted by a Park Ranger if one sees you metal detecting, this is just from my own experiences in similar situations.
If you got the posted "rules/regulations" from the park's website, look to see if they have a search function and if they do search for "metal detecting and or digging" and see if anything comes up, ......
au-seeker, thanx for chiming in. In my reply to the OP, I did warn that someone/anyone could indeed come up to debate the semantics of wordings. Yes, I have said in many posts that *just* because there's no *specifics* saying "no metal detectors", that anyone can still gripe, and tell you you're falling afould of the dreaded "alterations" and "digging" type clauses. Heck, why stop there? They can say you and I are falling afoul of the "taking", "removing" "collecting", and "harvesting" clauses as well! (which were put in places eons ago to prevent someone from thinking he could help himself to the swing sets, tan-bark, roses, etc..., but could, if you asked enough people, be applied to singular coins, pulltabs, etc...).
My answer to that is, that if someone does as you say, and expands his research to include search queeries like "dig", or "destroy", that you will indeed find verbage in EVERY city, EVERYWHERE, all parks that forbids such things. I mean, did you really think any park was going to say "sure! go ahead and '
destroy' the park" doh

But think about it au-seeker: all such verbage inherently infers the end-result. Does it not? So if you leave the area with no trace of your presence, then technically you have not destroyED anything, now have you? Even the term "dig" has an implicit connotation of the end result of "holes".
Now as I said to the OP, might someone come up and debate you on those semantics? Yes, it could happen. But if you plan ahead of time that your hobby is automatically equivalent to such terms (eg.: "metal detecting = destruction") and determine that such wording precludes you from detecting therefore, then give it up. Because I assure you, all public property has rules that forbid "destruction". Thus I do not consider those terms to be a necessary equivalent to metal detecting.
I wish there were a way to ensure that everyone loved us, and rolled out the red-carpet for us. I wish all archies loved us. I wish there were neon signs saying "damage and destruction and taking welcome here". But alas, that's not going to happen. It's a fact that not everyone is going to "love us and our hobby". It's kinda like nose-picking: Not technically "illegal", but ........ we all still use a little discretion on our timing, right? But if you ask enough people "can I pick my nose?" Someone will certainly tell you "no".