• journal_title：Geology
• Contributor：Kieran O'Hara ; William H. Blackburn
• Publisher：Geological Society of America
• Date：1989-
• Format：text/html
• Language：en
• Identifier：10.1130/0091-7613(1989)017<0524:VLMFTE>2.3.CO;2
• journal_abbrev：Geology
• issn：0091-7613
• volume：17
• issue：6
• firstpage：524

Mylonites from three widely separated localities along the Fries ductile deformation zone in the Blue Ridge province show substantial enrichments in trace and minor elements (TiO₂, P₂O₅, Zr, Y, and V) and depletions in Rb and Sr relative to the protolith. Two end-member hypotheses can explain the enrichments: one involves partitioning to and from an infiltrating fluid and assumes that all the elements were mobile. The second hypothesis assumes that the high-field-strength cations were largely immobile and that their enrichment is due to large volume losses in the mylonites. Modeling indicates that Ti is immobile for fluid/rock ratios as high as 10⁴, and petrographic and modal data support a volume-loss mechanism. Volume loss was accommodated by loss of SiO₂ and alkalies during feldspar dissolution. Calculated fluid/rock volume ratios required to produce the observed SiO₂ fosses (assuming Ti mobility) range from 70 to 600. Variable enrichments in P, Zr, Y, and V are attributed to selective mobility of these elements during fluid infiltration.