Search Results (4)

The Mazenod Lake region of the southern Great Bear Magmatic Zone (GBMZ) of the Northwest Territories, Canada, comprises the north-central portion of the Faber volcano-plutonic belt. Widespread and abundant surface exposure of several coalescing hydrothermal systems enables this paper to document, without ambiguity, the relationships between geology, structure, alteration, and mineralization in this well exposed iron-oxide–copper–gold (IOCG) mineral system. Mazenod geology comprises rhyodacite to basaltic-andesite ignimbrite sheets with interlayered volcaniclastic sedimentary rocks dominated by fine-grained laminated tuff sequences. Much of the intermediate to mafic nature of volcanic rocks is masked by low-intensity but pervasive metasomatism. The region is affected by a series of coalescing magmatic–hydrothermal systems that host the Sue–Dianne magnetite–hematite IOCG deposit and several related showings including magnetite, skarn, and iron oxide apatite (IOA) styles of alteration ± mineralization. The mid to upper levels of these systems are exposed at surface, with underlying batholith, pluton and stocks exposed along the periphery, as well as locally within volcanic rocks associated with more intense alteration and mineralization. Widespread alteration includes potassic and sodic metasomatism, and silicification with structurally controlled giant quartz complexes. Localized tourmaline, skarn, magnetite–actinolite, and iron-oxide alteration occur within structural breccias, and where most intense formed the Sue–Dianne Cu-Ag-Au diatreme-like breccia deposit. Magmatism, volcanism, hydrothermal alteration, and mineralization formed during a negative tectonic inversion within the Wopmay Orogen. This generated a series of oblique offset rifted basins with continental style arc magmatism and extensional structures unique to GBMZ rifting. All significant hydrothermal centers in the Mazenod region occur along and at the intersections of crustal faults either unique to or put under tension during the GBMZ inversion. Full article

In transtensional regions, structures striking obliquely to the extension direction generally exhibit oblique or partitioned slips. However, their on-fault partitioning patterns and controlling factors are less known, hindering our understanding of the evolution of the rifting process. Here, we study the slip distribution of the 2021 Mw6.7 Lake Hovsgol (Mongolia) earthquake occurred in a pull-apart basin using InSAR observations. Our preferred slip model shows a remarkable feature, with three zones exhibiting distinct slip directions at different depths. The Coulomb stress change analysis reveals that this pattern is likely controlled by the left-lateral motion of the Mondy Fault to the north, which also inhibits the growth of a boundary fault to the east of the lake, shaping the asymmetric graben structure in this region. Our results imply the important role of major strike-slip faults bounding the pull-apart basin in the formation and evolution of the oblique rift. Full article

The Dobi graben is a Quaternary, NW-trending continental rift found within the East-Central Block (ECB) of the Afar Depression (AD) in Ethiopia. The AD might be the only place where three active rifts meet on land. This diffused, Rift–Rift–Rift (RRR) triple junction in the ECB comprises the overlap zone between the Red Sea and the Gulf of Aden propagators. Rifting is ongoing in the Dobi graben as evidenced by the August 1989 earthquakes (of magnitude 5.7 < MW < 6.2). This study carried out a surface displacement time-series analysis to examine the kinematics of the Dobi graben and the surrounding area using 18 ascending orbit scenes (between May 2005 and March 2010) along tract 257 and 15 along the descending orbit (tract 006) of the Advanced Synthetic Aperture Radar (ASAR), C-band (λ = 5.6 cm) acquired by the ENVIronmental SATellite (ENVISAT). We utilized the Small Baseline Algorithm (SBA) techniques of the distributed scatterer, which were implemented independently to generate Line of Sight (LOS) displacement maps. These LOS displacement surface movements, identified in both geometries, can be interpreted as ± signs of predominantly vertical movement in both geometries: positive for uplifting and negative for subsidence. Additionally, opposite signs of ± horizontal movement in both geometries indicate that the movement is from East to West (or vice versa). Results from the velocity and displacement maps and time series analysis suggest that creeping is associated mainly with normal faulting and could be the primary mechanism for strain distribution for the Southeastern part of the Dobi graben. The anomalous, continuous uplifting exhibited at the rift shoulder and in the horst area might be linked to the presence of temporary reactivation of normal faulting in the region. The oblique, positive LOS signals observed in different parts of the Dobi graben might serve as a proxy for understanding how strain is accommodated as normal faulting and is distributed in a distinct northeast direction. This explanation supports both the arguments for the Northeast migration of the triple junction and the transfer of strain from the southernmost Red Sea Rift (RSR) to the Central AD. Full article

Bathymetric and seismic data provide insights into the geomorphological configuration, seismic stratigraphy, structure, and evolution of the area between Santorini, Amorgos, Astypalea, and Anafi islands. Santorini-Amorgos Shear Zone (SASZ) is a NE-SW striking feature that includes seven basins, two shallow ridges, and hosts the volcanic centers of Santorini and Kolumbo. The SASZ initiated in the Early Pliocene as a single, W-E oriented basin. A major reorganization of the geodynamic regime led to (i) reorientation of the older faults and initiation of NE-SW striking ones, (ii) disruption of the single basin and localized subsidence and uplift, (iii) creation of four basins out of the former single one (Anafi, Amorgos South, Amorgos North, and Kinairos basins), (iv) rifting of the northern and southern margins and creation of Anydros, Astypalea North, and Astypalea South basins, and (v) uplift of the ridges. Dextral shearing and oblique rifting are accommodated by NE-SW striking, dextral oblique to strike-slip faults and by roughly W-E striking, normal, transfer faults. It is suggested here that enhanced shearing in NE-SW direction and oblique rifting may be the dominant deformation mechanism in the South Aegean since Early Quaternary associated with the interaction of North Anatolian Fault with the slab roll-back. Full article