A giant sand injection complex: Processes and implications for basin evolution and subsurface fluid flow

Large clastic dykes (the Harutori‐Taro and Harutori‐Jiro dykes) and smaller dykes are exposed in the underground Kushiro Coal Mine (KCM), Japan. This study examines these dykes as a case study to investigate the geological conditions and fluid flow history that lead to the development of large clastic dykes in basins. The composition of the dykes indicates the Beppo and/or Harutori formations as their parent unit. Crystallite size distribution (CSD) analysis reveals Ostwald ripening of the kaolinite in the kaolinitised feldspar from the dykes, suggesting stagnant conditions in the parent unit before the dyke was formed. In contrast, smectite CSDs and the high carbonate content of the dykes suggest that large volumes of fluid flowed through the dykes along the established hydraulic gradient, which was triggered by the breaking of the upper seal. The isotopic and chemical compositions of the calcite and aragonite in the dykes, with moderate siderite and rhodochrosite content, indicate the fluid was a warm (>30°C) mixture of freshwater and saltwater, which was transferred from deeper levels of the parent unit towards the crest of an anticline. Immediately after sand injection, the semi‐closed system of the parent unit near the root of the large dyke was transformed into a major flow channel for overpressurised fluids. Subsequently, a large volume of fluid flowed along the vertical conduit (or dyke) over a long period of time (>1 Myr), which removed fluid from a widespread area (i.e., several hundred square kilometres) of the basin. The results show that thin parent units, poor lateral continuity of the upper seal, and spatially heterogeneous overpressurisation do not preclude the formation of large dykes.

show abstract

Controls on the genesis of a giant sand injection complex; insights into the Paleogene evolution of the stress of northern and central California

Vigorito,

Grippa,

Callow

2024

JGS

View full text Add to dashboard Cite

Giant sand injection complexes and localized swarms of sandstone intrusions are common in Upper Cretaceous to Miocene sedimentary successions of the Central and Northern California within a distance of less than 100 km from the Pacific margin of the North America Plate. One of the best preserved and extensively exposed injection complexes is the late Eocene Tumey Giant Injection Complex. The emplacement of sand injectites was driven by overpressure generated by thermal diagenesis of biosiliceous and smectite-rich mudstone host-rocks. The orientation and size distribution of sandstone intrusions was controlled by stress in which σ 1 and σ 3 were horizontal and, respectively, parallel and perpendicular to the present trace of the San Andreas Fault, and σ 2 was vertical. A strike-slip tectonic regime is inferred. Our analysis documents margin orthogonal extension and draws support for a late Eocene phase of increase of strain, and possibly active slip, along a syn-subduction strike-slip fault zone. Comparison with other injection complexes in the region indicates that the near-field maximum principal stress rotated through time, from normal to parallel with respect to the plate margin, probably in relation to variations of the relative motion vector of the converging plates.

show abstract

A giant sand injection complex: Processes and implications for basin evolution and subsurface fluid flow

Cited by 5 publications

References 72 publications

The Maracangalha injectite complex: An overlooked hydrocarbon play in the Lower Cretaceous Recôncavo Basin, NE Brazil

The Maracangalha injectite complex: An overlooked hydrocarbon play in the Lower Cretaceous Recôncavo Basin, NE Brazil

Geological conditions and fluid flow history that lead to the development of large clastic dykes in basins: A case study from Kushiro, Japan

Controls on the genesis of a giant sand injection complex; insights into the Paleogene evolution of the stress of northern and central California

Contact Info

Product

Resources

About