I have a 6 year old very authority site for my niche
and have a large article section that had all the articles
ranked first page on google.

Now google decides to NOT rank any of them!!!!
The entire article section of my site (over 250
articles!), which is directly linked off my homepage.

This is a 6 year old site with tons of backlinks and
great content.

I looked at my articles and remembered way back
when that I submitted the same articles to several
article sites that STILL rank first page google for
most of them.

Could it be, because of duplicate content?
I mean between my authority site and all the article sites
I submitted to back in the day?

Will google eventually find out they are good content or would
you advise I go back and tweak the articles on my site
to show google they are different than the article site
articles?

Google shows a regular and consistent caching of my
entire article directory, but rankings are GONE!

Now google decides to NOT rank any of them!!!!They're not in the index at all? Or they're not on the first page anymore? Are they in the supplemental index?

Could it be, because of duplicate content?Sure, it could be.

It could be your content competing with the matching content on the article sites, or it could be your content competing with itself. i.e., does every article have a unique page title and unique "description" meta tag?

Agree, it could well be a duplicate content issue if it's just the article pages that aren't being ranked, and there are no other problems with the indexing and ranking of the rest of your site.

It's worth publising an articl on your own site well before it's submitted to any others and ensuring that it gets indexed and ranks well before you consider publishing it on any other sites.

They're not in the index at all? Or they're not on the first page anymore? Are they in the supplemental index?

Sure, it could be.

It could be your content competing with the matching content on the article sites, or it could be your content competing with itself. i.e., does every article have a unique page title and unique "description" meta tag?

It is strange. If I type the entire title in, I can find some, but not very many. I haven't dug all the way through their thousands of pages, but I am most discouraged at the massive drop of all my articles.

Would it be worthwhile revising the articles on my site in hopes G will come back and see the changes and hopefully rank me again.

I am the authority site in my niche, and have been for over 6 years now.

*Now google decides to NOT rank any of them!!!!*

IMO that seems to point to something other than DC, I'd have expected at least some to keep their rankings if it was a DC filter....

Then what is it? I have not done anything different in 6 years of that site being 'live'. Completely innocent (white hat) strategies.

This is SO frustrating!

Is it just the article pages, or do you have a problem with any other pages on the site?

Put the url in your profile and we'll have a better idea...

BTW, have you submitted a site-map recently?