Evaluation of factors controlling smectite transformation and fluid production in subduction zones: Application to the Nankai Trough

• DOI: 10.1111/j.1440-1738.2008.00614.x
• Publication Date: 2008-02-14T22:54:49Z
• Authors: Demian M. Saffer; Michael B. Underwood; Alexander W. McKi...
• Keywords: Illite

Abstract The transformation of smectite‐group clay minerals to illite has garnered considerable interest as a potentially important process affecting both the mechanical and hydrologic behavior subduction zones. Illitization can generate fluid overpressure by release bound water, mineralogical change associated cementation may increase intrinsic frictional strength while decreasing sliding stability faults. Released water also contributes pore freshening observed in boreholes at numerous margins. Here authors combine data from Ocean Drilling Program drill sites along two transects Nankai zone with numerical models smectite transformation, (i) quantify distribution production downdip trench; (ii) evaluate its implications. High heat flow ( ca 180 mW/m 2 ) axis Kinan Seamount Chain (Muroto transect) initiates mineral outboard trench, whereas lower (70–120 100 km SW (Ashizuri results negligible presubduction diagenesis. As result, considerably more is subducted Ashizuri transect; simulated peak sources down‐dip trench are higher than for Muroto transect 1.2–1.3 × 10 −14 /s vs 6 −15 /s), shifted further trench. More generally, sensitivity analysis illustrates that flow, taper angle, incoming sediment thickness, plate convergence rate all systematically affect reaction progress These shifts loci volume constraining pathways, provide insight into links between fault mechanics.