the Cro-Mags' "Age of Quarrel" was released in 1988, and is a crushing example of hardcore punk infused with thrash metal.
I don't know what "thrash metal" is
The Cro-Mags took their time releasing songs that were, if I recall correctly, written much earlier.
So with 3 years of writing, a solid foundation of songs already in the band's repertoire, along with music from Harley's never released solo recording including "Don't Tread on Me," the Cro-Mags needed only a few more songs to complete the now classic set list. Those songs were completed with John Joseph and on November 2, 1984, and on February 16, 1985 the Cro-Mags went into High Five Studios and recorded 12 songs.http://www.cro-mags.com/history.htm
That moment in time when four very different freaks got together to make music was historic. The recordings made in that session were simply the blue print for all hardcore that followed and set the stage for the definitive hardcore album of all time, "The Age of Quarrel." This CD, now poignantly titled "Before the Quarrel" captured the raw fire that circumstances had created by bringing this unlikely group together. These recordings are revered as the pinnacle moment of the Cro-Mags and the favorite recordings of Cro-Mags fans.
The point stands, of course, but as a general rule, hardcore was dead in 1985, which was fortunate as proto-(death metal/black metal), grindcore, thrash and speed metal had just risen from its ashes 1983-1985. Hardcore lived on in what it influenced, which was fortunate because it was musically limited.
Proto-(death metal/black metal) 1983-1985
Slayer - Show No Mercy
Bathory - The Return
Hellhammer - Apocalyptic Raids
Sodom - In the Sign of Evil
Sepultura - Bestial Devastation
Possessed - Seven Churches
Honorable mention goes to Morbid Angel, who got "Abominations of Desolation" out in 1986, and Necrovore, who recorded at about the same time, beating Chuck Shuldiner and Death by a full two years and influencing their sound for the better (sadly, Chuck died of AIDS fourteen years later RIP).
DRI - Dirty Rotten LP
Cryptic Slaughter - Convicted
Napalm Death - From Enslavement... (I think)
Metallica - Kill 'Em All
Exodus - Pleasures of the Flesh
Nuclear Assault - The Plague
...and it was off to the races. All of these were heavily influenced by hardcore, most notably the British bands The Exploited and Discharge, but not alien to Black Flag and the Cro-Mags.