Abstract

Analogue experiments were used to investigate pluton emplacement during transpression in brittle crust. Models consisted of silicone putty placed within slots in a rigid basement and an overburden of dry sand. The models were transpressed, causing emplacement of silicone intrusions into the overlying sand. Space was made for intrusions by upward displacements of overburden along oblique reverse shear zones, in some cases accompanied by extensional shearing above the intrusions. Silicone putty was progressively accreted to the bases of uplifted blocks, and growing intrusions rode up the shear zones, leaving space for accretion of more silicone. The resulting intrusion shapes depended largely on the geometries of shear zone systems, which in turn depended on overburden thickness. The intrusion profiles and the structural relationships between intrusions and host in the experiments are comparable to some natural examples. A magma accretion model may thus account for pluton emplacement and batholith assembly within some transpressive orogens.

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