bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tectonic controls on magmatic-hydrothermal gold mineralization in the magmatic arcs of SE Asia
Authors: Barley M. E. , Rak P. , Wyman D. 
Published: April 2008

Abstract
The magmatic arcs of SE Asia contain some of the world’s major gold deposits. These are mainly related to magmatic-hydrothermal activity and include epithermal, porphyry Cu-Au and skarn deposits. Most gold deposits in SE Asian arcs formed during three intervals of tectonic reorganization rather than during periods of normal or steady-state subduction. These plate reorganizations and periods of gold mineralization were caused initially by the collision of the Australian craton with the Philippine Sea plate arc at 25 Ma. A second Mid-Miocene period of mineralization accompanied plate reorganization following maximum rotation or extrusion of Indochina and the cessation of spreading of the South China Sea at 17 Ma. However, the vast majority and largest deposits formed since 5 Ma in a broad belt from Taiwan to the Solomon Islands during an important period of tectonic reorganization. This tectonic reorganization accompanied a postulated change in the relative motion between the Indian-Australian and Pacific plates between 5 and 3.5 Ma following collision of the Philippine arc and the Eurasian plate in Taiwan. Arc-related magmatism in unusual tectonic settings produced the most abundant and largest deposits with many deposits associated with relatively rare high-K calc-alkaline, shoshonite, adakite and alkaline magmatism. In particular peak mineralization appears related to melting of mantle that had been previously modified by subduction. During large-scale plate reorganization this can occur at the end of a period of normal subduction, following the cessation of subduction, following arc collision or accompanying subduction reversal at approximately the same time in different parts of a complex system of magmatic arcs such as those in SE Asia. Such tectonic controls may be impossible to recognize in older orogenic belts where recognition of a major change in tectonic style and unusual magma types may be the best guides to mineralization.
Tectonics, geodynamics and gold mineralization of the eastern margin of the North Asia craton
Authors: Fridovsky Valeriy Yu. , Prokopiev Andrei V. 
Published: April 2008

Abstract
The North Asia craton is a crustal block including the Siberian platform and marginal fold-and-thrust belts. On the eastern margin of the North Asia craton there is the Verkhoyansk fold-and-thrust belt making up the western part of the Verkhoyansk-Chersky collisional orogenic belt extending for 2000 km from the Laptev Sea in the north to the Sea of Okhotsk in the south. A system of frontal thrusts separates the belt from the platform structures. The frontal part of the belt is mainly made of Carboniferous and Permian terrigenous rocks of palaeodeltas and submarine fans which grade eastward into Triassic and Jurassic sediments of the continental slope. The front of the belt is characterized by thrusting and strike-slip faulting with large horizontal displacements. The largest anticlinoria at the front of the belt have a duplex structure. Formation of the major gold deposits and fold and fault structures, as well as igneous activity in the region, are related to the collision of the North Asia craton with the Kolyma-Omolon superterrane and the Okhotsk terrane in the Late Jurassic-Neocomian. The collision occurred in two stages: the early Neocomian frontal collision and the late Neocomian oblique collision.
Supercontinents, superplumes and continental growth: the Neoproterozoic record
Authors: Condie Kent C. 
Published: April 2008

Abstract

Between 1300 and 500 Ma the Neoproterozoic supercontinent Rodinia aggregated (1300–950 Ma), broke up (850–600 Ma) and a new supercontinent, Pannotia-Gondwana, formed (680–550 Ma). Only
c.
11% of the preserved continental crust was produced during this 800 Ma time interval and most of this crust formed as arcs, chiefly continental margin arcs. At least 50% of juvenile continental crust produced between 750 and 550 Ma is in the Arabian-Nubian Shield and in other terranes that formed along the northern border of Amazonia and West Africa. An additional 20% occurs in Pan-African orogens within Amazonia, and
c.
16% in the Adamastor and West African orogens. The growth rate of continental crust between 1350 and 500 Ma was similar or less than the average rate of continental growth during the Phanerozoic of 1 km
3
/a, and this low rate characterizes both formation and breakup stages of the supercontinents.

The low rates of continental growth during the Neoproterozoic may be due to the absence of a superplume event associated with either Rodinia or Pannotia-Gondwana. If supercontinent breakup is required to produce a superplume event, perhaps by initiating catastrophic collapse of lithospheric slabs at the 660 km seismic discontinuity, the absence of a Meso-proterozoic-Neoproterozoic superplume event may mean that a Palaeoproterozoic supercontinent did not fully breakup prior to aggregation of Rodinia.
Sedimentary response to tectonics in extensional basins: the Pechelbronn Beds (Late Eocene to early Oligocene) in the northern Upper Rhine Graben, Germany
Authors: Derer C. , Kosinowski M. , Luterbacher H. P. , Schäfer A. , Süß M. P. 
Published: April 2008

Abstract
The deposition of the late Eocene to early Oligocene Pechelbronn Beds in the northern Upper Rhine Graben was controlled by changes in accommodation space, sediment supply and basin physiography, imposed by the syn-rift tectonic framework. Base-level cycles, defined by variations of the ratio of accommodation space to sediment supply (A/S ratio), allow untangling of the depositional history in this complex structural setting. A transfer zone divided the northern part of the Upper Rhine Graben into a southern and a northern sub-basin and created major depositional gradients. The low A/S ratio in the transfer zone led to sediment bypassing and cannibalisation. Only asymmetric cycles of fluvial and alluvial fan deposits developed, as the sediment was transported to the sub-basins. The higher A/S ratio on the major gradient of the southern sub-basin, which increased from the transfer zone to the south, allowed the formation of symmetric delta/shoreface and lacustrine cycles. At times starvation occurred in the transfer-zone-distal parts of the sub-basin. On subordinate scale, within the southern sub-basin, tilt-blocks bounded by growth faults created halfgrabens with inferior depositional gradients. On the footwall crest, due to low A/S ratio, bypassing and erosion occurred. Here asymmetric cycles of coarse-grained channel fill deposits were preserved. On the hangingwall, close to the normal fault, high A/S conditions were present and symmetric cycles developed. The creation of accommodation space kept pace and even outpaced the footwall-derived sediment supply, which created thick shallow water deposits.
Subsidence, stress regime and rotation(s) of a tectonically active sedimentary basin within the western Alpine Orogen: the Tertiary Piedmont Basin (Alpine domain, NW Italy)
Authors: Carrapa B. , Bertotti G. , Krijgsman W. 
Published: April 2008

Abstract

The Oligocene to Miocene Tertiary Piedmont Basin (TPB) is located in the NW part of Italy at the junction between the Apennine and the Alpine thrust belts. The position of the TPB on top of the Alpine/Apennine Orogen poses fundamental questions as to the tectonics of the basin subsidence. Having undergone little deformation, the TPB sediments provide an insight into the stress regime and rotations in the kinematically very complex area surrounding the basin itself. In this study we integrate subsidence and structural analysis with measurements of magnetic susceptibility anisotropy (AMS) and natural remanent magnetization (NRM) in order to better constrain the tectonic kinematics of the basin evolution. A major important period of subsidence occurred in the Middle Miocene involving the whole basin. During this period the TPB experienced NE-SW-directed compression and limited shortening. Some NW-SE-directed compressional features have been identified and they were probably active during post Tortonian times. Structures associated with north-south tension are quite common, but the amount of strain that they accommodate is minor. In addition this research provides new preliminary data suggesting counterclockwise rotation in the TPB by
c
. 20° which has taken place during Middle Miocene time.
Active or passive continental margin? Geochemical and Nd isotope constraints of metasediments in the backstop of a pre-Andean accretionary wedge in southernmost Chile (46°30′-48°30′S)
Authors: Augustsson C. , Bahlburg H. 
Published: April 2008

Abstract

Provenance analysis of siliciclastic sedimentary rocks gives indications of the tectonic evolution and setting of source regions and the rocks contained in them. The composition of sedimentary rocks ideally reflects the nature of these regions, and only indirectly the tectonic setting of the basin where the erosional debris is deposited. This makes it possible to interpret Late Devonian to Early Carboniferous metasedimentary basement rocks of the Andes in southernmost Chile as having been deposited at a passive margin, despite geochemical indications of an active margin setting for the source rocks, and the position of the metasediments in the backstop of an accretionary wedge. Major and trace elements point to felsic source rocks from an active margin environment. The Nd model ages of 1170–1490 Ma indicate that the source rocks were part of an old continental crust in the Late Palaeozoic. The ɛ
Nd
(T) values range between −7 and −2. These characteristics, in combination with the regional geology, suggest that the geochemical signal is dominated by rocks formed at an active margin, which later acted as feeders for the sediments deposited in a passive-margin environment. If corroborated by research in progress this emphasizes the problem of deducing the tectonic setting of a depositional basin from provenance data.
Effects of rate and nature of synkinematic sedimentation on the growth of compressive structures constrained by analogue models and field examples
Authors: Nalpas T. , Gapais D. , Verges J. , Barrier L. , Gestain V. , Leroux G. , Rouby D. , Kermarrec J.-J. 
Published: April 2008

Abstract
Compressive basins show various geometries of growth structures. In this paper, we examine the effects of the rate and nature of synkinematic sedimentation by comparing analogue models and field examples. We performed different types of experiments in order to simulate various natural conditions, the parameters tested including the rate of synkinematic sedimentation and the presence of a potential décollement layer deposited during deformation. Modelling techniques are similar to those usually used for experiments on brittle-ductile systems made of sand and silicone putty.

To study the influence of the synkinematic sedimentation rate, we used sets of experiments with different velocity ratios
R
between the rate of sedimentation (
V
s
) and the rate of uplift of the top of the structure (
V
u
). In standard experiments, we deposited only sand during deformation. In all experiments, growth folds and growth faults developed. The geometry of growth folds changes from a steep anticline for
R
=1, to a rounded broken anticline when
R
exceeds 2. The geometry of growth reverse faults changes: from segments which initiate with a dip angle of about 30°, but then flatten or steepen, for
R
=1/2 and for
R
=1, respectively. For some sets of experiments, a thin silicone layer deposited instead of sand at some stage of sedimentation simulated the introduction of potential décollement layers.

When a change in the nature of synkinematic sedimentation occurs between the two flanks of a fold, a fault develops in the flank where brittle material dominates. The direction of growth folds forming during compression in front of a ramp and above a décollement layer is parallel to the ramp and oblique to the direction of bulk shortening.
Good correlations are observed between experimental geometries and field examples from the southern Pyrenees (Eastern Ebro Basin and Jaca Basin, Spain) and the Apennines (Italy).
The role of spectral curvature mapping in characterizing subsurface strain distributions
Authors: Wynn T. J. , Stewart S. A. 
Published: April 2008

Abstract

The curvature of structured geological surfaces can be used to assess the degree of strain they have undergone. In many hydrocarbon reservoirs, this strain is expressed as brittle fracturing that may significantly impact reservoir performance. Here we describe the development of an algorithm for measuring the curvature of gridded surfaces derived from seismic data. For any grid node, the algorithm calculates the magnitude and orientations of the two principal curvatures,
K
1
and
K
2
, from which other curvature measurements can be derived, such as Gaussian curvature and summed absolute curvature (
K
1
+
K
2
). The algorithm has also been used to generate plots of summed absolute curvature as a function of grid node separation (
k
versus λ). These ‘spectral’ or
k
λ plots can be generated for each grid node and allow the definition of short-wavelength, high-amplitude noise cut-off lengths. They also deliver intermediate wavelength features such as fault drag or buckle folding and the identification of long-wavelength (basin-scale) curvatures. Portions of these data can be collapsed into single values by calculating the integral of the
k
λ curve. Further filters designed to screen the effects of background tectonic, or non-tectonic, curvatures can be applied to the
k
λ integral.

This algorithm has been tested using data from several North Sea chalk fields. A range of alternative types of curvature and curvature spectra are compared with other approaches to curvature calculation and other factors relevant to the calibration of such techniques in terms of the distribution of brittle fractures in sedimentary rocks.

The
k
λ integral provides a relatively simple approach to calculating the degree of multi-wavelength strain present at a particular grid node. Freeing algorithms from the restriction of the ‘arbitrarily’ selected minimum grid node spacing is a key step towards calibrating measured curvature against strain mechanisms. However, care must be taken to separate intrinsic and tectonic curvatures when generating and interpreting
k
λ plots and their integrals.
Reservoir characterization for the management of stress-sensitivity
Authors: Smart Brian G. D. , Somerville Jim McL. , Jin Min , Koutsabeloulis Nicos C. 
Published: April 2008

Abstract
Reservoir stress-sensitivity operates at the near-wellbore and the reservoir scale. While the near-wellbore effects have been recognized and managed for some time, awareness of the significance of the reservoir scale effects is only now developing, aided by extreme examples such as Ekofisk, HP/HT reservoirs and unconsolidated sands. Fractured reservoirs must also be considered to be stresssensitive, with this possibly being masked in the past by high productivities and abundant reserves. It is proposed that the appropriate conceptual model for all reservoirs is that of intact blocks of rocks bounded by discontinuities (fractures and bedding-parallel), loaded by an anisotropic stress state. This model should be used to drive the collection of stress-sensitive reservoir characterization data, knowing that the new generation of coupled simulators can usefully accommodate this data set. The data set listed enables all aspects of reservoir stress-sensitivity to be examined.
Geological evidence of patterns of fluid flow through fracture networks: examination using random realizations and connectivity analysis
Authors: Jolly Richard J. H. , Cosgrove John W. 
Published: April 2008

Abstract
Fluid flow through fractured media is dependent upon a variety of parameters including fracture length, orientation and density, and also on the relative magnitude of the lithostatic stress and the fluid pressure. Because of this it is often difficult to determine the fluid pathway through a particular fracture system even when the geometry of the network is known. Although many fluids (e.g. gas, water etc.) leave little or no evidence of their passage through the rock others such as magmas and fluidized sediments preserve the pathways they follow by forming dykes and sills.
It is found that the pathways preserved by the two types of fluids are different i.e. the spacing of the clastic dykes follows a power-law distribution and that of the igneous dykes a log-normal distribution. It is suggested that this in part might reflect the different properties of the dyke material (specifically its permeability) which determines whether or not the fracture containing the dyke can continue to act as a channel of easy fluid migration once the dyke has been emplaced.
Cenozoic strike-slip faulting from the eastern margin of the Wilkes Subglacial Basin to the western margin of the Ross Sea Rift: an aeromagnetic connection
Authors: Ferraccioli Fausto , Bozzo Emanuele 
Published: April 2008

Abstract
Tectonic modelling of regional aeromagnetic anomaly patterns suggests Cenozoic right-lateral strike-slip faulting along an inherited fault system of the Transantarctic Mountains and adjacent hinterland. We name it here the Prince Albert Fault System. The Reeves Fault and David Fault are Cenozoic right-lateral strike-slip faults and form part of the NW-SE-striking segment of this complex fault system, extending to the eastern margin of the Wilkes Subglacial Basin. Our aeromagnetic interpretation suggests therefore that the Wilkes Subglacial Basin may be connected to the Cenozoic strike-slip kinematic framework of the Transantarctic Mountains and western Ross Sea Rift. The southernmost segment of the Prince Albert Fault System parallels the N-S-striking McMurdo Sound Fault Zone and, together with it, defines a transtensional western Ross Sea Rift margin. High-resolution aeromagnetic images define the Cape Roberts pull-apart basin and suggest that Cenozoic magmatism may have focused along the transtensional western Ross Sea Rift margin itself.
Late Palaeozoic formation and development of the St Marys Basin, mainland Nova Scotia, Canada: a prolonged record of intracontinental strike-slip deformation during the assembly of Pangaea
Authors: Murphy J. B. 
Published: April 2008

Abstract
The Late Palaeozoic evolution of the St Marys Basin, mainland Nova Scotia, preserves evidence of protracted dextral shear along an intracontinental fault zone during collisional orogenesis and the assembly of Pangaea. The St Marys Basin formed within the E-W-trending Minas Fault Zone (MFZ) along the boundary between the Avalon and Meguma terranes and contains latest Devonian-Tournaisian continental clastic rocks that are 3000–4000 m in thickness.

The origin and evolution of the basin is attributed to either discrete or progressive dextral strike-slip tectonics along the MFZ between the Late Devonian and Late Carboniferous. Evidence for the Late Devonian origin of the basin is recorded along its southern flank by the fabrics of the deformed
c.
370 Ma granites, the overall sedimentary facies distribution, and some syndepositional features within the clastic rocks. The most intense deformation within the basin is concentrated in a relatively narrow ENE-trending zone, in which predominantly fine-grained clastic rocks are deformed into periclinal folds and related reverse faults. The orientation of this zone relative to the MFZ is consistent with dextral shear. At least some of this deformation occurred after the deposition of the overlying Visean Windsor Group. The style of deformation along the present northern margin of the basin (the Chedabucto Fault) is also consistent with regional dextral shear.

The St Marys Basin is an example of basin development and evolution adjacent to an intracontinental fault zone associated with oblique convergence during orogenesis. Its evolution provides constraints on the potential relationship between the termination of the mid-Palaeozoic Acadian orogeny, subsequent basin development, and the ongoing interactions between the Avalon and Meguma terranes, and between Laurentia and Gondwana during the assembly of Pangaea. More generally, because the relationship between fabric development and motion along intracontinental strike-slip faults in continental zones is difficult to interpret, the sedimentology and structural geology in basins developed along these fault zones may preserve a less ambiguous record of the main tectonic events.
Geometry, kinematics and scaling properties of faults and fractures as tools for modelling geofluid reservoirs: examples from the Apennines, Italy
Authors: Cello G. , Tondi E. , Van Dijk J. P. , Mattioni L. , Micarelli L. , Pinti S. 
Published: April 2008

Abstract

The study of some major fault zones in the Apennines was mostly focused on the acquisition of quantitative data
in situ
aimed at deriving input parameters for modelling faulted rock volumes. Structural data collected in the Monte Alpi area (southern Italy) and in the central Apennines allowed us to: (i) estimate the fractal dimension characterizing the geometric complexity and size distribution of different fault and fracture patterns; (ii) assess the appropriate parameters defining the overall architecture, anisotropy and related permeability structure of the mapped fault zones; and (iii) constrain the scaling properties of some of the attributes (i.e. length, spacing, map pattern, fracture density, etc.) of both fault-related and regional fracture sets.

The results of our work suggest that the above data are appropriate for extrapolating field based information at different scales, and for producing 3D models of fault and fracture networks.
3D finite element model of major tectonic processes in the Eastern Mediterranean
Authors: Heidbach O. , Drewes H. 
Published: April 2008

Abstract

A three-dimensional finite element model of the Eastern Mediterranean was developed in order to investigate the tectonic processes and model parameters which are mainly responsible for the observed surface deformation. The main faults are modelled as surfaces with Coulomb friction. Boundary conditions are slab pull at the Hellenic arc and the displacement for the African and Arabian plate taken from the rigid plate model NUVEL-1A. The rheology is elasto-visco-plastic. By varying the model properties a set of parameters can be determined which leads to a minimal mean deviation comparing the velocity field of the models with the space geodetic observations at 42 sites from global positioning system (GPS) and satellite laser ranging (SLR). The best result was attained with a low friction coefficient between 0.2 and 0.45 along the subduction zones and the main faults, a slab pull stress of 150 MPa and different cohesive strengths
C
in areas with compressional (
C
= 460 MPa) and extensional tectonic regimes (
C
= 40 MPa). The velocity field of the models shows the overall pattern of a westward escape of Anatolia and the SSW movement of the Aegean region.
3D discrete kinematic modelling of sedimentary basin deformation
Authors: Cornu T. , Schneider F. , Gratier J. -P. 
Published: April 2008

Abstract
3D coupled backward and forward deformation of geological layers is a new step in basin modelling. This problem can be treated with a mechanical or a kinematic approach. Because of the difficulties met with the mechanical approach, the kinematic approach is more often used. The kinematic model described here allows a geologically acceptable path to be built, which takes into account an incremental evolution of time. To obtain a better description of 3D geometries, the model uses a full hexaedric discretization. The discrete neutral surface of each layer is used to perform the flexural slip deformation.