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Abstract: Jupiter''s moon Io possesses numerous tectonic mountains in addition to its ubiquitous volcanoes and volcanic features. Remarkably, a distinct global anticorrelation exists between the spatial distribution of mountains and volcanic centers on Io. This relationship indicates an explicit connection between volcanism and mountain formation, even though the mountains are tectonic in origin (predominantly upthrusted crustal blocks). Spherical harmonic analysis shows the distribution of mountains and volcanic centers have statistically significant power at degree 2; this result is especially striking for the volcanic center distribution, and directly implicates models of asthenospheric tidal heating. The latter predict enhanced heat flux along the equator in a degree-two pattern that matches observations. Mountain formation on Io appears to be a form of dominantly vertical tectonism unique in the modern Solar System: continual burial by widespread volcanism drives the crust inward, which leads to strong compression, and at discrete locations, mountains. Correlation coefficients between the volcanic and mountain distributions indicate statistically meaningful anticorrelation at low spectral degrees (l =1, 2, 4, and 6); the anticorrelation is especially significant between the longitudinal (sectorial) l =2 components when considered on their own. We compare this anticorrelation with published models that link volcano and mountain formation. While consistent in part with l =2 convection models, which predict such an anticorrelation (in principle), such low degree anticorrelations are also (if not more) compatible with mountain formation due to, or influenced by, thermal expansion of Io''s crust, and deep compression and thrust faulting in regions of lower than average volcanic heat-piping. Positive correlations between mountain and volcanic center distributions at high spectral degree may reflect structural links between a good fraction of mountain blocks and adjacent volcanic paterae, whereas the anticorrelation at low degree implies that most volcanic features (which are far more numerous overall) form independently of mountains. [Copyright &y& Elsevier]

Abstract: Large scale tectonic mode switches from lithospheric shortening to lithospheric extension may play a fundamental role in the tectonometamorphic evolution of orogens located along convergent plate margins. Short-lived episodes of lithospheric extension can be inferred from the concomitant occurrence of bimodal magmatism, rapid exhumation of rock units, activity of extensional shear zones, steep geothermal gradients and, possibly, topographic collapse of the orogenic belt. Here we provide a synthesis of existing data from the European Alps, supporting the hypothesis on tectonic mode switches. Data are interpreted to suggest that at ca. 38–34Ma a period of N–S (orogen perpendicular) shortening led to the formation of medium to ultra-high-pressure mineral assemblages by lithosphere-scale thrust imbrication. A tectonic mode switch took place at ca. 34Ma, marked by the onset of E–W extension. During this extensional event, internal units of the Western and Central Alps were rapidly exhumed to mid-crustal level in the footwall of regional-scale extensional shear zones. Tectonic thinning was also accomplished through pervasive E–W stretching of the nappe pile. Lithospheric stretching resulted in the onset of an anomalous thermal regime, which was responsible for the overprint of the older medium- to ultra-high pressure mineral assemblages by Barrovian-type mineral assemblages and by migmatization. At the same time, attenuation of the isotherms led to partial melting of mantle lithosphere and to bimodal magmatism. Contemporaneous topographic collapse of the orogen is suggested by the deposition in the foreland of flysch units rich in minerals that were probably derived from erosion of the Early Oligocene calc-alkaline volcanics erupted in the hinterland. This short-lived episode of lithospheric stretching took place in no more than 4myr, from ca. 34Ma to ca. 32–30Ma. Renewed lithospheric thickening, which is observed in seismic tomography studies, resulted in large-scale folding of the extensional structures and the in rapid generation of topographic relief, feeding abundant clastic sedimentation in the peripheral basins. [Copyright &y& Elsevier]

Tectonic and metamorphic correlation in ancient (Proterozoic) orogenic terrains has always been problematic. This is because of the lack of a suitable reference frame to correlate deformation and metamorphic events from one orogenic terrain to another. Measurement of porphyroblast inclusion trails as Foliation Intersection/Inflection Axes (FIA) allows the chronological and kinematic linking of deformation as well as metamorphism. FIA measurements in the Mesoproterozoic Mount Isa and Georgetown inliers of the North Australian Craton have revealed two separate orogenic events (O1 and O2), which not only correlate better within the orogen but also between the two terrains. Microstructural corelations have also been made with the Mesoproterozoic rocks of the SW USA. Hence, porphyroblast inclusion trails as FIA provide a new reference frame to help correlate orogenic terrains. [ABSTRACT FROM AUTHOR]

Abstract: Unveiling how the interaction of friction (μ), pore pressure (p) and normal stress (σ n) controls the shear strength distribution along megathrust faults at convergent plate boundaries is crucial to our understanding of processes leading to the occurrence of devastating earthquake and the construction of mountains. An existing density model of the Chilean margin (18°–45°S) allows the computation of the so-called Vertical Stress Anomaly (VSA) that accounts for the component of normal stress due to the weight of the overlying crustal column. A spatial correlation between VSA, surface geology and several earthquake parameters suggests a significant control exerted by the geologically-dominated density structure of the crust on megathrust shear strength. The very seismogenic forearc in front of the high Central Andes (18°–34°S) has positive VSA values (up to 60MPa) and a mafic-dominated crust, which suggest high values of shear strength at the megathrust that are partially controlled by the weight of a dense forearc crustal column, in addition to a likely dry subduction channel characterized by high-μ and low-p. In contrast, the Southern Andean forearc (34°–45°S) shows neutral-to-negative VSA (down to −30MPa) correlated with a felsic-dominated crust, which added to a presumably wet subduction channel (low-μ and high-p) configures a rather weak megathrust below a light forearc. Earthquakes here are concentrated around the Arauco peninsula, a first-order morpho-structural anomaly characterized by comparatively higher values of VSA than the rest of this segment, which is the nest of the giant (Mw 9.5) Valdivia 1960 earthquake and the southern rupture termination of the recent Mw 8.8 Maule earthquake. The ultimately giant size of the 1960 earthquake resulted from rupture propagation along a 1000km long region characterized by negative VSA values. The correlation between VSA and the along-strike segmentation of the Andean orogen indicates that the geologically-inherited density structure of the forearc also rules long-term mechanical coupling between converging plates and prescribes the possible structure of the orogen. Because Central and Southern Andes represent two extremes in terms of orogenic structure and seismogenic behavior, results presented here have significant implications for the general comprehension of processes occurring at short and long time scale at convergent margins. [Copyright &y& Elsevier]

The Pressure–Temperature–time–deformation evolution of the high- to ultra-high-pressure units of the Western Alps has been progressively refined in the last 40years, leading to several paradigm shifts in the understanding of orogenesis. This set of information, combined with Cretaceous–Tertiary plate kinematic reconstructions and Mesozoic palaeogeography, indicates that the Western Alps represent the amalgamation of a Cretaceous and an Eocene orogen, which developed at the expense of the Adriatic and European rifted margins, respectively. In the Cretaceous, NNE-directed drift of the Adriatic plate, parallel to the inherited Jurassic structural trends, led to the development of a highly oblique subduction boundary. In this setting, the Canavese Zone and parts of the Sesia Zone, derived from the hyper-extended Adriatic margin, underwent deformation and metamorphism at conditions ranging from sub-greenschist to eclogite facies. A Lower Eocene switch to NNW-directed motion, perpendicular to the rift-related Jurassic structural trends, culminated in the collision between the proto-Alps and the Briançonnais block at ca. 44Ma. As a result, the Briançonnais Domain and parts of its hyper-extended margin, preserved in the (U)HP Piemonte Units, were accreted to the orogen. Continued convergence was subsequently accommodated by subduction of the more external Valaisan basin and of the thinned European margin. The arrival of thick European continental crust at the subduction zone at ca. 35–30Ma marked the onset of the final continental collision. To a first order, the orogen grew through the progressive episodic accretion of units located towards north-westerly positions. Accretion of subducting units at the front of the orogen was coeval with kinematic reworking of tectonic contacts in the hangingwall units, locally resulting in renewed deformation/metamorphism. [Copyright &y& Elsevier]

The Patagonian Andes record a period of Cretaceous-Neogene orogenesis that began with the compressional inversion of a Late Jurassic rift called the Rocas Verdes basin. Detrital zircon ages from sediment that filled the southern part of the basin provide a maximum depositional age of ∼148 Ma, suggesting that the basin opened approximately simultaneously along its length during the Late Jurassic. Structural data and U-Pb isotopic ages on zircon from granite plutons near the Beagle Channel (55°S) show that basin inversion involved two stages of shortening separated by tens of millions of years. An initial stage created a small (∼60 km wide) thrust wedge that placed the basaltic floor of the Rocas Verdes basin on top of adjacent continental crust prior to ∼86 Ma. Structures and metamorphic mineral assemblages preserved in an exhumed middle to lower crustal shear zone in Cordillera Darwin suggest that this obduction was accompanied by south directed subduction of the basaltic crust and underthrusting of continental crust to depths of ∼35 km beneath a coeval volcanic arc. A subsequent stage of out-of-sequence thrusting, culminating in the Paleogene, shortened basement and Upper Jurassic igneous rock in the internal part of the belt by at least ∼50 km, forming a bivergent thrust wedge. This latter period coincided with the exhumation of rocks in Cordillera Darwin and expansion of the fold-thrust belt into the Magallanes foreland basin. This orogen provides an important example of how orogenesis initiated and led to continental underthrusting and obduction of basaltic crust during closure of a quasi-oceanic rift basin. [ABSTRACT FROM AUTHOR]

Abstract: Convergent plate margins occur when two adjoining tectonic plates come together to form either a subduction zone, where at least one of the converging plates is oceanic and plunges beneath the other into the mantle, or a collision zone, where two continents or a continent and a magmatic arc collide. Convergent plate margins are arguably the most complicated and dynamic plate boundaries on Earth and have been the subject of many investigations and discussions since the advent of plate tectonic theory. This paper provides a historical background and a review of the development of geological and geodynamic theories on convergent plate margins. Furthermore, it discusses some of the recent advances that have been made in the fields of structural geology, geophysics and geodynamics, which are fundamental to our understanding of this phenomenon. These include: (1) the finding that plates and plate boundaries move at comparable velocities across the globe; (2) the emerging consensus that subducted slabs are between two to three orders of magnitude stronger than the ambient upper mantle; (3) the importance of lateral slab edges, slab tearing and toroidal mantle flow patterns for the evolution of subduction zones; and (4) clear evidence from mantle tomography that slabs can penetrate into the lower mantle. Still, many first-order problems regarding the geodynamic processes that operate at convergent margins remain to be solved. These include subduction zone initiation and the time of inception of plate tectonics, and with it convergent plate margins, on Earth. Fundamental problems in orogenesis include the mechanism that initiated Andean mountain building at the South American subduction zone, the potential episodicity of mountain building with multiple cycles of shortening and extension, and the principal driving force behind the construction of massive mountain belts such as the Himalayas–Tibet and the Andes. Fundamental questions in subduction dynamics regard the partitioning of subduction into a trench and plate component, and the distribution of energy dissipation in the system. In seismic imaging, challenges include improving resolution at mid to lower mantle depth in order to properly understand the fate of slabs, and better constraining the 3-D flow-related anisotropic structure in the surrounding mantle. Future insights into such fundamental problems and into the regional and global dynamics of convergent plate margins will likely be obtained from integrating spatio-temporal data, structural geological data, geophysical data and plate kinematic data into plate tectonic reconstructions and three-dimensional geodynamic models of progressive deformation. [Copyright &y& Elsevier]

Abstract: The Early–Middle Miocene exhumation of the crystalline core of the Himalaya is a relatively well-understood process compared to the preceding phase of burial and prograde metamorphism in the Eocene–Oligocene. Highly deformed rocks of the Greater Himalayan Sequence (GHS) dominate the crystalline core, and feature a strong metamorphic and structural overprint related to the younger exhumation. The Tethyan Sedimentary Series was tectonically separated from the underlying GHS during the Miocene by the South Tibetan Detachment, and records a protracted and complex history of Cenozoic deformation. Unfortunately these typically low-grade or unmetamorphosed rocks generally yield little quantitative pressure–temperature–time information to accompany this deformation history. In parts of the western Himalaya, however, the basal unit of the Tethyan Sedimentary Series (the Haimanta Group) includes pelites metamorphosed to amphibolite facies. This presents a unique opportunity to explore the tectono-thermal evolution of crystalline rocks which record the early history of the orogen. Pressure–temperature–time–deformation (P–T–t–d) paths modelled for two Haimanta Group pelitic rocks reveal three distinct stages of metamorphism: (1) prograde Barrovian metamorphism to 610–620 °C at c. 7–8 kbars, with garnet growing over an early tectonic fabric (S1); (2) initial decompression during heating to 640–660 °C at c. 6–7 kbars, with development of a pervasive crenulation cleavage (S2) and staurolite and kyanite porphyroblast growth; (3) further exhumation during cooling, with minor retrograde metamorphism and modification of the pervasive S2 fabric. Monazite growth ages constrain the timing of initial garnet growth (>34 Ma), the start of D2 and maximum burial (c. 30 Ma), and the termination of garnet growth (c. 28 Ma). Muscovite Ar/Ar ages indicate cooling through c. 300 °C at c. 13 Ma, from which we derive an initial exhumation rate of c. 1.3 mm year−1 for the Haimanta Group. The underlying GHS was exhumed at a rate of 2.2 to 3 mm year−1 during this time. The difference in exhumation rate between these two units is considered to reflect Early Miocene displacement on the intervening South Tibetan Detachment. Slower exhumation (c. 0.6 mm year−1) of both units after c. 13 Ma followed the cessation of major displacement on this structure, after which time the Haimanta Group and the GHS were exhumed as one relatively coherent tectonic block. [Copyright &y& Elsevier]

Abstract: A high degree of correlation between present-day relative rock uplift measured using continuous GPS geodesy and spatially averaged surface elevations suggests that long-wavelength topographic relief is presently increasing along the southeastern flank of the Sierra Nevada range and within an adjacent portion of the northern Basin and Range province. Current estimates for erosion rate are an order of magnitude smaller than the relative rates determined by geodesy. Thus, although the uplift serves to enhance long-wavelength relief, it cannot be explained entirely as an isostatic response to erosion. If uplift rates have been constant through time, the duration over which the uplift could have been active (<1.6Myrs) is shorter than expected based on our current understanding of the geodynamic history of the region. One possible explanation for the observed present-day uplift pattern is that it represents an ongoing isostatic response to gradual reduction of the equivalent elastic thickness (EET) of the lithosphere under temporally constant loads. Another explanation is that the loads currently supporting the high elevations of the southern Sierra are evolving with time. According to either hypothesis, vertical surface motions may have slowly accelerated since ~mid-Pliocene time. Several possible mechanisms for progressive reduction of EET may be attributable to thermo-mechanical disequilibrium that began with the removal of an ultramafic root from the Sierran batholith during late Miocene or early Pliocene time. Specific mechanisms for ongoing enhancement of loads are less obvious. Based on these results, we suggest that dense networks of long-running continuous GPS stations around the world currently represent an underutilized resource for studies of orogenesis and upper mantle processes. [Copyright &y& Elsevier]

A synthesis of the main physical shapes of the area of Bocas del Toro archipelago is made by the author, and in conclusion gives some recommendations for a permanent and sustainable regional planning. [ABSTRACT FROM AUTHOR]

Abstract: Basin-averaged cosmogenic 10Be concentrations, apatite (U–Th)/He thermochronometry and incision into a dated palaeosurface constrain spatial and temporal variations in the rates of denudation experienced during the early-stages of orogenesis in the San Bernardino Mountains, California. Cosmogenic 10Be analysis measures denudation over intermediate (∼102–104 years) time scales and records rates which decrease from a maximum of 2700±500 mm ka−1 in the south to a minimum of 52±5 mm ka−1 in northern catchments. Corresponding rates from (U–Th)/He and incision into a dated palaeosurface measure long-term (∼106 years) denudation rates which decrease from between 1200±400 mm ka−1 in the south to a minimum of 30±20 mm ka−1 in the north. The temporal consistency observed in the broad-scale patterns of denudation rates probably results from the persistent imprint of the initial crustal architecture and drainage network. These have maintained an influence on slope distributions, and are thus fundamental factors controlling the gross patterns of denudation throughout the early stages of orogenesis. Where variations between the denudation rates measured over different time scales are apparent the intermediate-term rates are found to be consistently greater than the long-term, with the increase being more pronounced around the fault bounded peripheries of crustal blocks relative to quiescent block interiors. This provides empirical support for a model of mountain building whereby topographic development is dictated by the headward retreat of drainage systems that propagate away from zones of displacement. Our findings indicate that recent localised increases in denudation rates in young fault block orogens may be explained by a progressive denudational response to prior tectonic uplift, rather than a consequence of climatic change. [Copyright &y& Elsevier]

Abstract: The origin of high temperatures during regional low-pressure granulite facies metamorphism within the Proterozoic Broken Hill Block, Australia, has been reinterpreted to be the result of burial of anomalously hot rock packages for which the lithospheric geothermal gradient was initially elevated during early rifting ca. 1.71–1.67Ga, and then maintained during a ca. 1.62Ga short-lived mid-crustal extensional event. Mid-crustal extension at ca. 1.62Ga was associated with amphibolite facies metamorphism and elevated lithospheric geothermal gradients, and occurred prior to activity along D2 high-temperature shear zones, peak low-pressure granulite facies metamorphism (ca. 1.60Ga) and crustal shortening during the Olarian Orogeny (ca. 1.60–1.59Ga). This reinterpretation places the Broken Hill Block within an environment in which multiple episodes of transient extension (ca. 1.71–1.62Ga) were followed by a switch to shortening at ca. 1.60Ga. The interpreted tectonic environment is a continental back-arc setting located in the over-riding plate of a subduction zone along the southern margin of Palaeoproterozoic Australia. [Copyright &y& Elsevier]

Eastern Anatolia is the location of a young continent-continent collision between the Arabian and Eurasian plates. Long-period magnetotelluric data have been used to image the electrical resistivity of the crust and upper mantle in this region. The Anatolian block is being extruded to the west and is characterized by a low-resistivity (fluid rich) lower crust underlain by relatively normal upper mantle structure. The Anatolian Plateau has a lower crust that contains pockets of very low resistivity that may indicate local accumulations of melt. This is underlain by an upper mantle with an anomalously low resistivity that can be accounted for by an asthenosphere containing a few percent partial melt. The presence of fl uids may weaken the crust and mantle sufficiently to permit lateral flow, and may also allow a decoupling of the upper and lower portions of the lithosphere. The lithospheric structure of the Anatolian Plateau is similar to that of the northern Tibetan Plateau, with zones of elevated fluid content. However, low resistivity in the Anatolian crust is found in isolated pockets, rather than the widespread regions observed in Tibet. [ABSTRACT FROM AUTHOR]

Analysis of detrital zircon from previously geochronologically unconstrained metasedimentary rocks in the eastern Arunta region, using U - Pb LA-ICPMS and SHRIMP, provides ages reconcilable with Australian sources. Maximum depositional ages of the analysed samples fall into two groups, three samples having maximum depositional ages of ca 1780-1760 Ma and two at ca 2510-2490 Ma. Metamorphic monazite from two pelitic rocks provides bimodal age populations of 1773 ± 9 Ma and 325 ± 8 Ma from one sample, and 1719 ± 9 Ma and 341 ± 5 Ma from the second. The age of 1773 ± 9 Ma is the first direct evidence of monazite growth in the interval ca 1780-1770 Ma, and is attributed to high-grade contact metamorphism associated with the proximal emplacement of granodioritic bodies previously thought to be subduction-related. The metamorphic age of 1719 ± 9 Ma is attributed to the Strangways Orogeny (1730-1710 Ma). The Carboniferous ages of 325 ± 8 Ma and 341 ± 5 Ma in both samples are attributed to partial resetting and new growth of monazite during the Alice Springs Orogeny (ca 400-300 Ma). Sm - Nd isotope systematics of the metasedimentary rocks display a large variation ranging from εNd(1760) = - 1.4 to - 8.8 and, when coupled with the detrital-zircon age populations, allow for a locally derived (North Australian Craton) source for the metasedimentary rocks. Analysis of igneous zircon from a felsic layer of the Entia Gneiss Complex intimately interlayered with the metasedimentary rocks yielded a 207Pb/206Pb weighted average age of 1771 ± 10 Ma, interpreted as the crystallisation age of the igneous precursor. This age is indistinguishable within error from that of the granodioritic intrusions (Inkamulla Granodiorite 1773 ± 4 Ma), here thought to be responsible for the high-grade metamorphism in the metasedimentary rocks. Given that the granodioritic bodies have previously been characterised as subduction-related intrusions, the approximately coincident ages of metamorphism, deposition of at least some of the metasedimentary rocks, and the intrusion of voluminous felsic and mafic magmas, suggests that the deposition and metamorphism of the precursor to the metasedimentary rocks may be related to active subduction along the southern margin of the Arunta region. [ABSTRACT FROM AUTHOR]

Integrated structural, metamorphic and geochronological data demonstrate the existence of a contractional orogen preserved in the ca 1850 Ma Donington Suite batholith along the eastern margin of the Gawler Craton, South Australia. The earliest structures are a pervasive gneissic foliation developed in the Donington Suite and interleaved metasedimentary rocks. This has been overprinted by isoclinal and non-cylindrical folding, and zones of pervasive non-coaxial shear with north-directed transport, suggesting that deformation was the result of orogenic contraction. SHRIMP U - Pb zircon data indicate that a syn-contractional granitic dyke was emplaced at 1846 ± 4 Ma. Overprinting the contractional structures are a series of discrete, migmatitic high-strain zones that show a normal geometry with a component of oblique dextral shear. U - Pb zircon data from a weakly foliated microgranite in one such shear zone give an emplacement age of 1843 ± 5 Ma. Rare aluminous metasedimentary rocks in the belt preserve a granulite-grade assemblage of garnet + biotite + plagioclase + K-feldspar + silicate melt that formed at ∼600 MPa and ∼750°C. Peak metamorphic garnets are partially replaced by biotite + sillimanite+ cordierite assemblages suggesting post-thermal peak cooling and decompression, and are indicative of a clockwise P - T evolution. Chemical U - Th - Pb electron microprobe ages from monazites in retrograde biotite yield a minimum estimate for the timing of retrogression of ca 1830 Ma, indicating that decompression may be linked to the development of the broadly extensional shear zones and that the clockwise P - T path occurred during a single tectonothermal cycle. We define this ca 1850 Ma phase of crustal evolution in the eastern Gawler Craton as the Cornian Orogeny. [ABSTRACT FROM AUTHOR]

Abstract: The underlying cause of Indosinian thermotectonism remains unclear, in part because the term has also been adopted to explain Triassic orogenesis across southern China. This paper puts forward the case that use of the term Indosinian should be confined to Vietnam where deformation is linked to continental accretion as opposed to southern China where Triassic igneous activity, metamorphism and deformation are linked to the development of an active plate margin through north-directed subduction of the Pacific oceanic plate. A review of the regional palaeogeography, as well as palaeontological and thermochronological data, highlights the lack of evidence to support the Indosinian as a major mountain building event. There is no definitive evidence for Triassic collision between the Indochina and South China blocks. Preference is given to a plate tectonic model that explains the Indosinian as a reactivation event driven by accretion of Sibumasu block to Indochina. [Copyright &y& Elsevier]

Abstract: Evidence of two burial–exhumation cycles that took place during a single orogeny has been found in rocks belonging to the Piemonte unit of the Western Alps. An early high pressure event, which resulted from tectonic burial down to pressures of 1.5 GPa, was followed by exhumation to ca. 0.20–0.35 GPa as a result of extensional deformation. Renewed shortening culminated in a second burial episode down to pressures of 0.65–0.80 GPa, before the final exhumation took place. Existing geochronological data allow only ca. 13–19 Ma for the completion of both burial–exhumation cycles. Therefore, we suggest that the evolution of orogens is characterized by multiple short-lived burial–exhumation cycles related to orogen-scale alternance between shortening and extensional deformation. [Copyright &y& Elsevier]

Abstract: Seventy skarn-type gold deposits, including 1 super-large, 19 large and 24 medium-sized, are known from different geotectonic units of China. They contain a total resource of approximately 1000 t of gold (625 t in South China), and account for 20% of China''s gold reserves. These skarn deposits are sited in collisional orogenic belts, fault-controlled magmatic belts and reactivated cratonic margins. All of the Chinese skarn gold provinces were affected by Phanerozoic collisional orogenesis. The timing of the metallogenic events and the spatial–temporal distribution of the Chinese skarn gold deposits indicates that they were formed during ore-forming processes linked to the transition from shortening to extension in the geodynamic evolution of a collision orogen, and not to subduction systems as is commonly advocated for porphyry copper systems around the Pacific Rim. [Copyright &y& Elsevier]

Abstract: Among the south Asian Sericini only a very few endemic monophyletic lineages developed in the lowland areas, such as the taxa belonging to Maladera (subgenus Cycloserica). Twenty species of Sericini (Coleoptera: Scarabaeidae) representing the principal lineages of Maladera occurring in the Palearctic region were included in a parsimony analysis based on 37 morphological characters. Maladera (Cycloserica) was found be monophyletic, composed by a clade comprising (Maladera caspia (Cycloserica excisipes, Leucoserica arenicola)) being distributed in the Middle Asian lowlands and its sister group the Maladera quinquidens-group with four endemic species in the Himalayan and North Indian lowlands. The ranges of these two clades as well as of the sister group of Cycloserica reveal a separating effect by the uplifted Himalayan–Alpine belt. It is hypothesized that these two Cycloserica lineages existed before they dispersed into the two separated areas, the northern Indian subcontinent (Himalayas) and the Middle Asian lowland. Due to the sister group relationship of Cycloserica and Leucoserica, both nested deeply within the species of Maladera, it seems reasonable to consider both synonymous with Maladera. Based on this conclusion one new combination is necessary, Maladera (Cycloserica) arenicola, and Leucoserica Reitter, 1896, is placed in synonymy with Cycloserica Reitter, 1896). [Copyright &y& Elsevier]

By virtue of its large area of exposure of different crustal levels, and preservation of a protracted (~400 million years) Palaeoproterozoic to Mesoproterozoic tectonic evolution, the Mt Isa Inlier is an excellent natural laboratory to study Proterozoic tectonic processes. The inlier preserves evidence of intracontinental basin development, plutonism, low-pressure metamorphism, orogenesis at different crustal levels, and crustal-scale metasomatism. In addition, the Mt Isa Inlier is endowed with a variety of ore deposits, including the Mt Isa Pb – Zn – Ag and Cu deposits, Century Zn – Pb – Ag deposit, Cannington Ag – Pb – Zn deposit, and the Osborne and Ernest Henry iron oxide Cu – Au deposits. Basement rocks were deformed and metamorphosed during the ca 1900 – 1870 Ma Barramundi Orogeny and intruded by the granitic rocks of the ca 1850 Ma Kalkadoon and Ewen Batholiths and their coeval Leichhardt Volcanics. Three stacked and superimposed superbasins evolved between ca 1800 and ca 1595 Ma. These basins evolved in an environment characterised by elevated heat flow and transient episodes of magmatism and basin inversion in an inferred continental backarc setting. The ca 1600 – 1500 Ma Isan Orogeny probably records two phases of orogenesis. The first phase ( ca 1600 – 1570 Ma) involved approximately north – south to northwest – southeast shortening in which a northwest-vergent fold-thrust belt evolved in the Eastern Fold Belt and localised basin inversion occurred in the Western Fold Belt. The second phase ( ca 1550 – 1500) involved thick-skinned deformation in the Eastern and Western Fold Belts, characterised by upright folding, reverse faulting, and dextral wrenching. Voluminous granites were emplaced throughout the Eastern Fold Belt between ca 1550 and 1500 Ma. Exhumation and cooling of the crustal pile following the Isan Orogeny were related to crustal extension and widespread erosion in eastern and southern Australia. Subtle reactivation of faults within the inlier following the Isan Orogeny records the distal effects of Mesoproterozoic to Neoproterozoic breakup events and orogenesis in central Australia. [ABSTRACT FROM AUTHOR]

A fundamental change from thin-skinned to thick-skinned tectonics in the Mt Isa Terrane is interpreted to reflect a westward shift in the locus of crustal thickening during Mesoproterozoic orogenesis in northeastern Australia. Geochronological constraints indicate that west-directed, thin-skinned deformation in the eastern part of the terrane occurred before ca 1540 Ma. This upper crustal system is interpreted to link with deeper crustal thickening in the Georgetown Inlier to the east, where synorogenic granites intruded at ca 1550 Ma. This early system was dissected by basement-cutting reverse faults across the entire Mt Isa Terrane after 1540 Ma. The nature of deeper crustal tectonics within the Mt Isa Terrane is determined by evaluating possible origins for the crustal structure revealed in a seismic-refraction profile. In particular, alignment of shallowly west-dipping, mid-crustal, high-velocity layers is interpreted to reflect tectonic duplication of underplated crust. This crustal stacking fault is inferred to be the controlling structure for the thick-skinned deformation associated with the Isan Orogeny. [ABSTRACT FROM AUTHOR]

Abstract: The sediment archive, of material eroded from an active tectonic region and stored in adjacent basins, can provide a valuable record of hinterland tectonism especially when information in the source region itself is obscured by later metamorphism or removed by tectonism or erosion. Using the sediment record to document tectonism is a well established approach, but more recently there has been a burgeoning of the number of isotopic techniques which can be applied to detrital material, in particular single-grain analyses. Thus the scope for application of detrital studies to a number of different tectonic problems has widened considerably. In this review, the example of sediments eroded from the Himalayan orogen and preserved in the suture zone basin, foreland basin, remnant ocean basins and deep sea fans is used to illustrate the approach. Techniques as diverse as petrography, heavy mineral, XRF and Sr–Nd studies; single grain dating by Ar–Ar, U–Pb and fission track methodologies; and single grain Sm–Nd and Pb isotopic analyses, are described. The paper documents how the sediment record can be used to determine the thermal and tectonic evolution of the orogen, constrain mechanisms of continental deformation, exhumation rates and palaeodrainage. [Copyright &y& Elsevier]

Importants fluctuations of the lake of Nicaragua levels had been observed during the Quaternary. The lake appears to be a conjugated factors of the Rivas isthmus Quaternary orogenesis, the Nicaragua's grabben neotectonic and the arrival of sedimentary floods (fans) from the Central and Guanacaste volcanic ranges in Costa Rica: [ABSTRACT FROM AUTHOR]

The southern margin of the Pilbara Craton in northwestern Australia underwent regional heating, folding, and thrusting as well as extensive fluid flow during collision in the Paleoproterozoic. However, the precise tinting of this event is uncertain. Previous geochronologic studies of Archean basement rocks have yielded a wide range of younger radiometric dates (from ca. 2.4 Ga to ca. 2.0 Ga), interpreted to record multiple hydro- thermal alteration events. In situ U-Pb geochronology of authigenic monazite and xenotime in very low grade Archean metasedimentary rocks from across the craton suggests that the Pilbara was affected by at least two cryptic thermotectonic events, the first between ca. 2430 Ma and ca. 2400 Ma, and the second between ca. 2215 Ma and ca. 2145 Ma. The older event is restricted to three localities in the west, and its cause is unknown. The younger event affected most of the craton (>100,000 km²), spanning a 70 m.y. period from ca. 2215 Ma nearest the collisional margin in the south, to ca. 2145 Ma toward the craton interior in the north. The widespread geographic and stratigraphic distribution of ca 2.2 Ga phosphates suggests that fluid flow was pervasive. This event was probably driven by the northward-advancing Ophthalmian fold-and-thrust belt that developed during protracted collision. The associated low-grade metamorphic front migrated over ∼350 km at an average rate of ∼5.0 mm/yr, placing important constraints on the rate and duration of deformation and metamorphism in orogenic settings. [ABSTRACT FROM AUTHOR]

Field mapping, structural analysis, and geochronologic data from northwestern Nepal reveal major normal right-slip motion along a previously unrecognized west-northwest striking system of shear zones that we term the Gurla Mandhata-Humla fault system (GMH). The GMH obliquely cuts across the Greater Himalayan Crystalline sequence and into the Lesser Himalayan imbricate thrust belt via two right-step-over structures. The average slip direction on the GMH parallels the strike of the Himalayan orogen. Motion along this fault system has resulted in an apparent left separation of the South Tibet Detachment, Main Central thrust zone, and Lesser Himalayan imbricate thrust belt along a north striking segment of the fault system. We estimate a minimum of 21 km of net slip on the southern branch of the GMH by restoring the trace of the Main Central thrust zone parallel to the average slip direction on the fault. Taking into account slip estimates from the northern branch of the GMH yields a minimum net slip estimate of 24.4 to 32.4 km for the GMH. The 232Th/208Pb ion microprobe monazite ages from leucogranite bodies indicate that motion on the GMH occurred after 15 Ma. Its initiation immediately followed crustal thickening between the Main Central thrust zone and Indus-Yalu suture zone. Motion on the GMH is contemporaneous with arc-normal contraction in the southernmost Himalayan orogen. These observations can be explained by a model that involves foreland propagating structural systems facilitating arc-normal contraction in the foreland and arc-parallel extension in the hinterland that work together to maintain the arcuate shape of the Himalayan orogen. [ABSTRACT FROM AUTHOR]

Abstract: During Upper Triassic to Lower Jurassic time, arc magmatic rocks of the Stikine terrane, arc-marginal sediments of the Whitehorse Trough, igneous and mantle rocks of the Cache Creek ‘ophiolite’ and Kutcho assemblage, and oceanic sedimentary and volcanic rocks of the Cache Creek terrane represented a magmatic arc, forearc basin, forearc basement, and subduction complex, respectively. The Cache Creek subduction complex was thrust to the southwest over the Whitehorse Trough forearc basin and the Stikine terrane in the Middle Jurassic during collision with an inboard continental domain. Interpretation of the various lithotectonic assemblages of the northern Intermontane belt in terms of a new plate tectonic model has a number of important implications for the Canadian Cordillera: (a) the model allows comparisons to be drawn with available seismic reflection interpretations of Cordilleran crustal structure; (b) ‘ophiolite’ emplacement was achieved by ramping of forearc oceanic lithosphere onto thick crustal parts of a subducting plate during collisional orogenesis; (c) island–arc collision and accretion were the principal mechanisms for continental growth with relatively minor contributions from ‘sliced-off’ oceanic seamounts and/or plateaux; and (d) some terrane-bounding faults such as the Nahlin Fault do not represent major lithospheric-scale boundaries and their importance in tectonic reconstructions has been overemphasised. [Copyright &y& Elsevier]

The Balakot Formation of the Himalayan foreland basin in Pakistan was originally described as a >8 km thick clastic red bed succession within which are stratigraphically intercalated four gray marl bands containing fossils dated at 55-50 Ma. On this basis, and the reported conformable contact with the underlying Paleocene Patala Formation, the Balakot Formation red beds were interpreted as tidal facies dated at 55-50 Ma, by >20 Myr the oldest foreland basin sediments eroded from the metamorphic orogen. However, our new detailed structural mapping shows the Balakot Formation to be in tectonic contact with the underlying Patala Formation, and the marl bands to be structurally intercalated with the red beds. Hence neither the nature of the Balakot Formation lower contact nor the intercalated marl bands can be used to date the red beds. Our Ar/Ar dating of 257 individual detrital white micas from the Balakot Formation red bed sandstones shows that the red bed succession must be younger than 37 Ma, and we thus conclude that the first exposed foreland basin continental sediments eroded from the metamorphic mountain belt were deposited after 37 Ma, at least 15 Myr later than previously believed. These new structural, stratigraphic, and isotopic data from the Balakot Formation provide new constraints to the early tectonic evolution of the mountain belt, result in reassessment of the facies and provenance of the Balakot Formation, and force reconsideration of models of orogenesis, basin evolution, and the timing and diachroneity of India-Asia collision that are based on the original documentation of the Balakot Formation. [ABSTRACT FROM AUTHOR]

A research on the Mesozoic fill-sequences of Hefei basin, located at the north foot of Dabie Mountains, shows two-phase evolution. The first phase, early- to mid-/late-Jurassic, is characterized by terrestrial clastic deposits, with four times of reverse-grading units at least, and forms greatly thick molass reconstruction in the mid-/late-phase, which reflects gradually strong thrusting-orogenesis in the north Dabie and flexural depression in the north foreland of Dabie Mountains. The second phase, late-Jurassic to Cretaceous, includes two-episode rifting processes. The first episode (J3) shows calc-alkalic and alkali volcanic rocks interstratified pyroclastic rocks, which may reflect upwelling igneous magma from mantle-source due to the Yangtze continent slab breakoff induced by deep subduction process. A suite of lacustrine, fluvial and piemount facies, about 3000 –3500 m in thickness, develops in the second episode (J3-K1), which reflects regional extensional setting and intense elevator diversity of mountain-basin in the study area. This research renews and deepens cognition for the Mesozoic Dabie orogenesis [ABSTRACT FROM AUTHOR]

Hypersaline (Na–Ca–Cl) fluids are associated with late-stage quartz veining and retrogression of garnet, kyanite and other high P–T phases in the vicinity of thrusts and major lithological boundaries in the Scandian nappes of the Troms-Ofoten region, northern Norway. They record early Devonian fluid infiltration during rapid exhumation in the final stages of Caledonian orogenesis. The δ18O and δD characteristics of these late fluids provide compelling evidence for deep circulation of meteoric fluids. The sub-greenschist to low greenschist facies retrogression (P=2±1 kbar; T =300–350 °C) suggests infiltration to depths of 7–9 km in a regime of supra-hydrostatic fluid pressure. Peak metamorphic quartz veins and associated fluids have δD and δ18O characteristics consistent with a metamorphic origin (δD -47 to -75; δ18O+8.6 to +17.4). However, late quartz veins and associated fluids show a broad spread of δD from -42 to -148, interpreted in terms of meteoric fluid infiltration. Such negative δD values are only recorded in present-day high-latitude or high-altitude settings, and since north Norway was in an equatorial setting (10° S) in the early Devonian, a high-altitude origin is deduced. By calculation, and by comparison with modern examples, the early Devonian mountains of the north Norwegian Caledonides are interpreted to have had a topography in excess of 5 km. The deep circulation of surface waters is interpreted in terms of topographically driven flow, linked with a hydrothermal system induced by elevated geothermal gradients due to rapid uplift. Whilst the case for deep penetration of surface-derived fluids has been promoted for Mesozoic and younger mountain belts, this study represents one of the first documented examples for a Palaeozoic orogenic belt. It suggests that many of the fundamental processes operating during the exhumation of mountain belts are similar irrespective of age. [ABSTRACT FROM AUTHOR]

The India-Asia collision zone is the archetype to calibrate geological responses to continent-continent collision, but hosts a paradox: there is no orogen-wide geological record of oceanic subduction after initial collision around 60-55 Ma, yet thousands of kilometers of post-collisional subduction occurred before the arrival of unsubductable continental lithosphere that currently horizontally underlies Tibet. Kinematically restoring incipient horizontal underthrusting accurately predicts geologically estimated diachronous slab break-off, unlocking the Miocene of Himalaya-Tibet as a natural laboratory for unsubductable lithosphere convergence. Additionally, three endmember paleogeographic scenarios exist with different predictions for the nature of post-collisional subducted lithosphere but each is defended and challenged based on similar data types. This paper attempts at breaking through this impasse by identifying how the three paleogeographic scenarios each challenge paradigms in geodynamics, orogenesis, magmatism or paleogeographic reconstruction and identify opportunities for methodological advances in paleomagnetism, sediment provenance analysis, and seismology to conclusively constrain Greater Indian paleogeography., (© The Author(s) 2022. Published by Oxford University Press on behalf of China Science Publishing & Media Ltd.)

New fieldwork and tectonic analysis has been carried out along the Andean morphotectonic frontline between 46°30' and 47°30′S. The right lateral transtensional Marques–Zeballos Pass fault system (MZPRS) controlled the 800–1200 m uplift of the Andes at 16.1–18.1 Ma. Our data and analysis indicate that there was no lower Miocene contractile event along the Andean morphotectonic frontline. The Main Andean Thrust (MAT), which is deeply rooted in the upper crust is a retroarc thrust dipping 10–15° westward, and provides evidence for major crustal shortening at ~120 Ma. At that time the arc volcanic strata of the Ibañez Fm (148–178 Ma) was transported eastward above the rift volcanic Quemado Fm (144179 Ma), which lies unconformably on the Deseado basement massif. The geologic records from the fieldwork together with the available data allow us to identify the processes controlling the dynamic evolution of the two main topographic features of the studied Andean segment. (1) Upward convection originating from the subducted South Chile Ridge −1 segment (SCR −1) is dynamically sustaining the high topography of the North Patagonian Icefield (4070 m at the Mt. San Valentin, ~2 km higher than the Southern South Volcanic Zone). This, together with the locus of maximum moisture being at 47°S during glacial events has resulted in producing the two largest glacial lobes of Patagonia. (2) The 180 km long, E –W trending antiformal arch structure of the Mt. Zeballos Ridge (MZR, a hinge zone trending N–S along the MZPRS) straddling the Andes and the Foreland is proposed to be the morphological "twin" of the South American Plate Moho Plateau (SAM MOHO P). The SAM MOHO P controls the location of both the MZPRS and the MZR boundaries location through time. The Patagonia Slab Window and SAM asthenospheric dynamics (upward and corner flows, respectively) and their in–depth interaction appear to control the morphotectonic evolution of the whole studied segment through a powerful feedback loop between tectonics, morphology, and climate, at least for the past 3–4 Myr. [ABSTRACT FROM AUTHOR]

The geodynamic system of Earth is controlled by the horizontal motion of fragmented tectonic plates due to complex interaction between the mantle and the crust. Land and marine paleomagnetic signatures, along with extensive petrochronological and structural data, suggest non-continuous, multi-directional convergence histories for modern orogenic belts, as seen in the Himalayas and Betic Cordillera, among others. The consequences of radical changes in the direction of plate motions are obscured by complex structural settings and repeated cycles of metamorphism in orogenic belts. Although, subduction was operational on Earth in the Paleoproterozic, one of the major questions is: how far back in geological time can we trace the scale of modern-style subduction, collisional tectonics and poly-metamorphism? The metasedimentary and volcanic rocks (2.5 to 2.05 Ga) of the Sodankylä belt of northern Finland were deformed and metamorphosed during a prolonged period, now represented by the Svecofennian orogen (ca. 1.92–1.77 Ga). The orogenic belt represents a window into the deep levels of a Paleoproterozoic crust, where the interplay between deformation and metamorphism can be compared with the modern orogenic settings. In this study, five discrete heterogeneously developed superimposed, near-orthogonal, deformation events (D1 to D5) have been identified and mapped based on the high-resolution aeromagnetic data and field studies. Regional correlation of tectonic fabrics, along with metamorphic textures across the Sodankylä belt and northern Finland, suggest that each deformation event was a regional-scale phenomenon rather than a local one. Previous geochronological data obtained from the Sodankylä belt and adjacent Central Lapland Granitoid Complex on different Paleoproterozoic deformed rocks allow us to propose a time-constrained tectono-metamorphic model for the Sodankylä belt. The sequence of near-orthogonal deformation history and the polymetamorphic evolution offer comparisons with modern-style orogenic settings. The most notable aspect is the occurrence of Mesoarchean and Paleoproterozoic eclogitic high-pressure granulites reported from the Belomorian belt of Fennoscandian Shield, which lies to the east of the Sodankylä belt. From a tectono-metallogenic viewpoint, the Sodankylä belt is located in the centre of Ni-Cu-PGE, orogenic gold-cobalt deposits of the northern part of Fennoscandian Shield, therefore, the tectonic processes and overprinting role of multiple deformation phases need to be well understood as they directly link mineral exploration to the timing and controls on mineralization. [ABSTRACT FROM AUTHOR]

Granitic plutons of the Wangetti and Mt Formartine Supersuites intrude the Hodgkinson Formation of the Macalister Range district of the eastern Hodgkinson Province, north Queensland, Australia. Field and microstructural analyses of country-rock fabrics and those of the granites show four deformational events (D1–D4) for the district, in common with other sectors of the Hodgkinson Province. Structural relationships show that plutons of the two supersuites were emplaced at different times. The Wangetti Granite lacks fabric development, but the deflection of country-rock cleavage trends around it and the microscale crenulation of S2 on the rims of D4 porphyroblasts within its aureole indicate syn-D4 emplacement, consistent with the Early Permian crystallisation age attributed to this pluton from isotopic evidence. Plutons of the Mt Formartine Supersuite show the effects of multiple (D2–D4) deformation. An emplacement age of 357 ± 6 Ma (latest Devonian) was obtained for this granite by SHRIMP U–Pb analyses of zircon. This identifies an early episode of plutonism for the Hodgkinson Province, most granites from which are of Permian age. The new date constrains the age of D2 for the Macalister Range district and the age of the protolith of the Hodgkinson Formation as pre-Carboniferous. It matches the age previously determined for one of several small, related granitic stocks in the southeastern Camel Creek Subprovince of the Broken River Province. Structural relationships for granites of this age suggest that their emplacement was broadly associated with the first episode of regional-scale orogenesis and the development of penetrative fabrics in the Hodgkinson – Broken River Fold Belt. [ABSTRACT FROM AUTHOR]