LOCATION: The outcrops are located on the unnamed tributary to Fairforest Creek south of McClure Creek. Park at the gate on S-42-12 located 0.4 miles north of the intersection of Lancaster Road and S-42-12. Walk east along the track and turn right (south, downhill) at the second deerstand down to the creek. (Fig. 9, Jonesville quad)
DESCRIPTION: In a traverse of several hundred meters along this tributary, it is possible to see mafic metavolcanic rocks intruded by an undeformed, unmetamorphosed diorite. In fact the diorite intrudes the contact between mafic metavolcanic rocks and diorite gneiss (Stop 7). The diorite contains foliated xenoliths of mafic metavolcanic rocks (Fig. 12) and mappable blocks of metagabbro and diorite gneiss (Fig. 8) of the Mean Crossroads complex. The orientation of the metamorphic fabric in these xenoliths and blocks is consistent with the orientation in the country rock and at a high angle to the intrusive contact. The diorite gneiss at this location also contains equant (spherical?) mafic enclaves (Fig. 13). Petrographic examination of the undeformed diorite shows igneous textures and mineralogy is preserved (Fig. 14). Every indication is that this rock is a post-metamorphic pluton.
Dennis and Wright (1993, 1996) dated three size fractions of zircon from the diorite at this site by the U-Pb method and interpreted the resulting upper intercept at 535+/-4 Ma as a crystallization age. Comparing this age with that reported by Dennis and Wright (1993, 1996) for Mean Crossroads metadiorite-diorite gneiss, one concludes that the metamorphic fabric observed in these rocks of the Charlotte belt must be older than 535+/-4 Ma. The Acado-Baltic fossils from the Carolina slate belt reported by Samson and others (1990) are middle Cambrian in age. Thus, we conclude that the metamorphic fabric observed here did not form as a consequence of collision of the Carolina arc with Laurentia, but must record events on the fringes of Gondwana (Dennis and Wright, 1995). Jim Hibbard and Scott Samson (1995) have correlated this deformation with the Virgilina orogeny of Glover and Sinha (1973).
(Top Left) Fig. 12. Foliated xenolith in undeformed, unmetamorphosed diorite, Stop 6. Foliation orientation is at a high angle to the contact, and is consistent with orientations of foliation outside the pluton.
(Top Right) Fig. 13. Equant mafic enclave within undeformed, unmetamorphosed diorite, Stop 6.
(Bottom) Fig. 14. Photomicrograph of undeformed, unmetamorphosed diorite, showing good igneous texture and mineralogy, Stop 6. Field of view approximately 25 mm. Plane and X-polar views.