This study documents an eruptive center, the instrusive Flat River complex and associated Carolina slate belt volcanic rocks near Durham, North Carolina. The zircon Pb/U age of the granite, granodiorite, quartz diorite, gabbro Flat River complex is 650 ± 30 m.y. Local vent breccias, chilled and protoclastically deformed margins, and petrographic comparisons with the experimental results in the qz-ab-or system confirm that the Flat River complex was emplaced at a depth of less than 1 km and was locally surface breaking. Thus, the Flat River can be viewed as a very shallow fossil volcanic magma chamber and may be typical of many granitoid plutons in the Carolina slate belt.

The Flat River was intruded into a pile of coarse, near-vent pyroclastic deposits and lavas of felsic to intermediate composition. Intercalated in these is an exhalative unit of thinly layered to laminated metachert and iron oxide. Shallow to deep (or quiet) probably marine conditions prevailed. Some subaerial pyroclastic rocks may be present in the older parts of this >650-m.y. to 620-m.y.-old sequence of volcanic rocks.