Stress-induced smectite dehydration: ramifications for patterns of freshening and fluid expulsion in the N. Barbados accretionary wedge

摘要: Abstract Presented is new experimental evidence that smectites can partially dehydrate from 18.5 A to 15.4 hydrates when they are subjected effective mineral framework stresses above 1.3 ± 0.3 MPa. We show here this process substantially freshen saline pore fluids and impact our understanding of the hydrogeologic processes in convergent margins where abundant. The general anomalous freshening N. Barbados accretionary wedge was previously proposed relate widespread lateral expulsion derived dehydration reactions at great depth. In contrast, analysis suggests a significant part relates stress-induced smectite occurred during Ocean Drilling Program (ODP) water extraction process. Clear for long-distance flow appears be limited localized chloride isotopic anomalies developed 20 m thick, locally mineralized region top decollement horizon Site 948. Our reinterpretation consistent with fluid zone being (1) highly transient on time scales several hundreds years, (2) channeled laterally into heterogeneous finger-like paths apparently not intersected, and/or sampled by drilling most regions toe wedge. incipient may also buffering situ pressures wedge, maintaining ˜1.3 MPa.