Publication Date:
2017-04-04
Description:
The factors controlling the development of different types of fault rock assemblages and, more specifically,
the formation of friction melts are still not fully understood. In this study we compared two
exhumed strike–slip faults in the Adamello batholith (Southern Alps): the Gole Larghe and the Passo
Cercen fault zones, active at 9–11 km depth and temperatures of 250–300 C. Each fault zone consists of
hundreds of sub-parallel strands exploiting pre-existing joints. The Gole Larghe fault strikes N105 5
and is dextral; the fault rocks are cataclasites and widespread, centimetre-thick pseudotachylytes. The
Passo Cercen fault strikes on average N130 and is formed by multiple fault horizons: fault segments
striking N105 –N130 are mainly dextral, whereas faults striking N135 –N140 are mainly sinistral.
Microstructural, mineralogical and geochemical investigations show that the fault rocks are cataclasites
associated with thick epidote þ K-feldspar þ quartz veins and rare, millimetre-thick pseudotachylytes.
Field evidence suggests that in both fault zones, the direction of the maximum horizontal stress s1 was
N135 . The Gole Larghe fault strikes at about 30 to s1 and is favourably oriented for reactivation. By
contrast, the Passo Cercen fault strikes at low angles to s1 and is unfavourably oriented for reactivation,
therefore requiring the development of high pore pressures, as suggested by the occurrence of extensive
epidote veining and hydraulic breccias. It is proposed that frictional melting in the Passo Cercen fault
zone was inhibited by the development of high pore pressures and low effective normal stresses.
Description:
Published
Description:
1511-1524
Description:
3.1. Fisica dei terremoti
Description:
JCR Journal
Description:
reserved
Keywords:
earthquakes
;
pseudotachylytes
;
04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
