Fault-controlled dolomitization in the Montagna dei Fiori Anticline (Central Apennines, Italy): record of a dominantly pre-orogenic fluid migration

The Lower Jurassic platform and basinal deposits exposed in the Montagna dei Fiori Anticline (Central Apennines, Italy) are pervasively affected by dolomitization. Based on the integration of field work, petrography, and geochemistry, two fault-related dolomitization events were recognized and interpreted as having occurred before and during the Apenninic orogeny. Fluid inclusion analysis indicates moderate to elevated salinity values of 3.5 to 20.5 and 12.8 to 18.6 eq. wt % NaCl in the first and the second event, respectively. The estimated salinities, in combination with [delta].sup.18 O values and .sup.87 Sr/.sup.86 Sr ratios, suggest significant involvement of evaporitic fluids in both events, most likely derived from the underlying Upper Triassic Burano Formation. In addition, the .sup.87 Sr/.sup.86 Sr ratios up to 0.70963 suggest the circulation of deep-sourced fluids that interacted with siliciclastic rocks and/or the crystalline basement during the dolomitization events.