Structural fabric evidence for indentation tectonics in the Nambucca Block,southern New England Fold Belt,New South Wales

Structural studies of Lower Permian sequences exposed on wave‐cut platforms within the Nambucca Block, indicate that one to two ductile and two to three brittle — ductile/brittle events are recorded in the lower grade (sub‐greenschist facies) rocks; evidence for four, possibly five, ductile and at least three brittle — ductile/brittle events occurs in the higher grade (greenschist facies) rocks. Veins formed prior to the second ductile event are present in some outcrops. Further, the studies reveal a change in fold style from west‐southwest‐trending, open, south‐southeast‐verging, inclined folds (F₁ ⁰) at Grassy Head in the south, to east‐northeast‐trending, recumbent, isoclinal folds (F₁ ⁰; F₂ ⁰) at Nambucca Heads to the north, suggesting that strain increases towards the Coffs Harbour Block. A solution cleavage formed during D₁ in the lower grade rocks and cleavages defined by neocrystalline white mica developed during D₁ and D₂ in the higher grade rocks. South‐ to south‐southwest‐directed tectonic transport and north‐south shortening operated during these earlier events. Subsequently, north‐northeast‐trending, open, upright F₃ ² folds and inclined, northwest‐verging, northeast‐trending F₄ ² folds developed with poorly to moderately developed axial planar, crenulation cleavage (S₃ and S₄) formed by solution transfer processes. These folds formed heterogeneously in S₂ throughout the higher grade areas. Later northeast‐southwest shortening resulted in the formation of en échelon vein arrays and kink bands in both the lower and higher grade rocks. Shortening changed to east‐northeast‐west‐southwest during later north‐northeast to northeast, dextral, strike‐slip faulting and then to approximately northwest‐southeast during the formation of east‐southeast to southeast‐trending, strike‐slip faults. Cessation of faulting occurred prior to the emplacement of Triassic (229 Ma) granitoids. On a regional scale, S₁ trends east‐west and dips moderately to the north in areas unaffected by later events. S₂ has a similar trend to S₁ in less‐deformed areas, but is refolded about east‐west axes during D₃. S₃ is folded about east‐west axes in the highest grade, multiply deformed central part of the Nambucca Block. The deformation and regional metamorphism in the Nambucca Block is believed to be the result of indenter tectonics, whereby south‐directed movement of the Coffs Harbour Block during oroclinal bending, sequentially produced the east‐west‐trending structures. The effects of the Coffs Harbour Block were greatest during D₁ and D₂.     

Country‐rock structural fabrics as a guide to pluton emplacement depth: An example from the Hodgkinson Province,northeastern Australia

Country‐rock structures adjacent to plutons of the linear, northwest‐southeast‐trending Mt Alto Supersuite, Hodgkinson Province, northeastern Australia, are variably developed from north to south along the belt. S₃ and S₄ cleavages show close temporal relationships with pluton emplacement and are better and more widely developed around plutons in the north, whereas much weaker cleavages of the same generation are only sporadically developed to the south. Cleavage trend lines anastomose around less elongate plutons to the north but are generally truncated by more elongate plutons to the south. It is proposed that a major crustal dislocation, the Alto Fault Zone, comprises a set of subparallel structures that formed prior to granite intrusion and controlled emplacement of some plutons and their final shapes. The north‐south variation in structural relations is interpreted to reflect a corresponding variation in depth of emplacement from north to south, which resulted when post‐emplacement reactivation of the Alto Fault Zone uplifted and sinistrally displaced the northern end of the supersuite relative to the southern end. Reactivation of the fault zone after granite emplacement is supported by the truncation of some plutons.     

A tale of two synclines: Rifting,inversion and transpressional popouts at Lake Julius,northwestern Mt Isa terrane,Queensland

This study reviews the origin of two approximately east‐west‐trending synclines in the Lake Julius area at the eastern edge of the Leichhardt Rift. The genesis of one of these structures can be found in a north‐south shortening event (D₁) that occurred at the beginning of the compressional Isan Orogeny (at ca 1600 Ma). Metasediments in a cross‐rift were rammed against a competent buttress defined by the pre‐existing rift architecture, producing the approximately east‐west‐trending Somaia Syncline and its associated axial‐plane slaty cleavage. In contrast, the Lake Julius Syncline was produced by reorientation of an originally approximately north‐south‐trending (D₂) fold, in a transpressional zone adjacent to a strike‐slip fault, at the end of the Isan orogeny. The effects of late fault movement can be partially reconstructed, based on correlations assuming that regionally developed trains of upright folds formed during the peak of the Isan Orogeny (D₂). These folds have been offset, as well as having been tightened and disrupted at the same time as fault movements took place. The overall pattern of movement in the Lake Julius region can be explained as the result of an ‘indentor’ ramming into the ancient edge of the Leichhardt Rift, which acted as a buttress.     

Deformation history and timing of granite emplacement in the Butchers Hill — Helenvale region,northern Hodgkinson Province,Queensland

Granite plutons of the Whypalla Supersuite in the Butchers Hill — Helenvale region of north Queensland were intruded into the upper crust of the Hodgkinson Formation during contractional deformation associated with the Permian‐Triassic Hunter‐Bowen Orogeny. A four‐stage structural history has been resolved for the area, with fabric overprinting relationships, porphyroblast‐matrix microstructural geometries and isotopic ages being consistent with granite emplacement during D₄ shortening at ca 274 Ma. Microstructural relationships suggest the possibility of a minor syn‐D₃ phase of granite emplacement. The deformation‐emplacement history of the Butchers Hill — Helenvale area is consistent with that recognised regionally for the Hodgkinson Province, indicating province‐wide synchronous syntectonic granite intrusion during a major phase of contractional deformation. Intense syn‐emplacement deformation partitioning was ongoing in the country rocks during progressive D₄ and was associated with upward translation of country rock from the microscale to the macroscale along D₄ cleavages and shears. Kinematic indicators show that this progressive uplift, at the scale of the area examined, was east‐side‐up.     

Variable hangingwall palaeotransport during Silurian and Devonian thrusting in the western Lachlan Fold Belt: Missing gold lodes,synchronous Melbourne Trough sedimentation and Grampians Group fold interference

The western margin of the Lachlan Fold Belt contains early ductile and brittle structures that formed during northeast‐southwest and east‐west compression, followed by reactivation related to sinistral wrenching. At Stawell all of these structural features (and the associated gold lodes) are dismembered by a complex array of later northwest‐, north‐ and northeast‐dipping faults. Detailed underground structural analysis has identified northwest‐trending mid‐Devonian thrusts (Tabberabberan) that post‐date Early Devonian plutonism and have a top‐to‐the‐southwest transport. Deformation associated with the initial stages of dismemberment occurred along an earlier array of faults that trend southwest‐northeast (or east‐west) and dip to the northwest (or north). The initial transport of the units in the hangingwall of these fault structures was top‐to‐the‐southeast. ‘Missing’ gold lodes were discovered beneath the Magdala orebody by reconstructing a displacement history that involved a combination of transport vectors (top‐to‐the‐southeast and top‐to‐the‐southwest). Fold interference structures in the adjacent Silurian Grampians Group provide further evidence for at least two almost orthogonal shortening regimes, post the mid‐Silurian. Overprinting relationships, and correlation with synchronous sedimentation in the Melbourne Trough, indicates that the early fault structures are mid‐ to late‐Silurian in age (Ludlow: ca 420–414 Ma). These atypical southeast‐vergent structures have regional extent and separate significant northeast‐southwest shortening that occurred in the mid‐Devonian (‘Tabberabberan orogeny’) and Late Ordovician (‘Benambran orogeny’).     

Deformation Stages and Ar‐Ar Age Data of the Wan‐Zhe‐Gan Tectonic Zone,Southeast China,and Their Tectonic Significance

The major tectonic zone that passes through the border regions of the Anhui, Zhejiang, and Jiangxi Provinces in southeast China has been commonly referred to as the Wan-Zhe-Gan fault zone. Geologically, this zone consists of several regional fault belts of various ages and orientations. We have categorized the faults into four age groups based on field investigations. The Neoproterozoic faults are northeast striking. They start from the northeast Jiangxi Province and extend northeastward to Fuchuan in Anhui Province, the same location of the northeast Jiangxi-Fuchuan ophiolite belt. The faults probably acted? during the Neoproterozoic as a boundary fault zone of a plate or a block suture with mélange along the faults. The nearly east-west- or east-northeast-striking faults are of Silurian ages (40Ar/39Ar age 429 Ma). This group includes the Qimen-Shexian fault and the Jiangwang-Jiekou ductile shear belt. They represent a major tectonic boundary in the basement because the two sides of the fault have clear dissimilarities. The third group of faults is north-northeast striking, having formed since the early-middle Triassic with 40Ar/39Ar ages of 230–254 Ma. They form a fault belt starting from Yiyang in northern Jiangxi and connect with the Wucheng as well as the Ningguo-Jixi faults. This fault belt is a key fault-magmatic belt controlling the formation of Jurassic-Cretaceous red basins, ore distribution, magmatic activity, and mineralization. When it reactivated during the late Cretaceous, the belt behaved as a series of reverse faults from southeast to northwest and composed the fourth fault group. Therefore, classifying the Wan-Zhe-Gan fault zone into four fault groups will help in the analysis of the tectonic evolution of the eastern segment of the Jiangnan orogen since the Neoproterozoic era.     

Basin shape and sediment architecture in the Gun Supersequence: A strike‐slip model for Pb–Zn–Ag ore genesis at Mt Isa

Sequence‐stratigraphic correlations provide a better understanding of sediment architecture in the Mt Isa and lower McNamara Groups of northern Australia. Sediments record deposition in a marine environment on a broad southeast‐facing ramp that extended from the Murphy Inlier in the northwest to the Gorge Creek, Saint Paul and Rufous Fault Zones in the southeast. Depositional systems prograded in a southeasterly direction. Shoreline siliciclastic facies belts initially formed on the western and northern parts of the ramp, deeper water basinal facies occurred to the east and south. The general absence of shoreline facies throughout the Mt Isa Group suggests that depositional systems originally extended further to the east and probably crossed the Kalkadoon‐Leichhardt Block. Fourteen, regionally correlatable fourth‐order sequences, each with a duration of approximately one million years, are identified in the 1670–1655 Ma Gun Supersequence. Stratal correlations of fourth‐order sequences and attendant facies belts resolve a stratigraphic architecture dominated by times of paired subsidence and uplift. This architecture is most consistent with sinistral strike‐slip tectonism along north‐northeast‐oriented structures with dilational jogs along northwest structures as the primary driver for accommodation. Although reactivated during deformation, the ancestral northwest‐trending May Downs, Twenty Nine Mile, Painted Rocks, Transmitter, Redie Creek and Termite Range Fault Zones are interpreted as the principal synsedimentary growth structures. Sinistral strike‐slip resulted in a zone of long‐lived dilation to the north of the May Downs/Twenty Nine Mile and Gorge Creek Fault Zones and a major basin depocentre in the broad southeast‐facing ramp. Subordinate depocentres also developed on the northern side of the ancestral Redie Creek and Termite Range fault zones. Transfer of strike‐slip movement to the east produced restraining or compressive regions, localising areas of uplift and the generation of local unconformities. Northwest‐ and north‐northeast‐oriented magnetic anomalies to the south and west of Mt Isa, identify basement heterogeneities. Basement to the south and west of these anomalies is interpreted to mark intrabasin siliciclastic provenance areas in the Gun depositional system. Pb–Zn–Ag deposits of the Mt Isa valley are interpreted as occurring in a major basin depocentre in response to a renewed phase of paired uplift and subsidence in late Gun time (approximately 1656 Ma). This event is interpreted to have synchronously created accommodation for sediments that host the Mt Isa deposit, while focusing topographically and thermobarically driven basinal fluids into the zone of dilation.     

Geological observations in high‐grade mid‐Proterozoic rocks from Else Platform,northern Prince Charles mountains region,east Antarctica

Granulite facies rocks on Else Platform in the northern Prince Charles Mountains, east Antarctica, consist of metasedimentary gneiss extensively intruded by granitic rocks. The dominant rock type is a layered garnetbiotite‐bearing gneiss intercalated with minor garnet‐cordierite‐sillimanite gneiss and calc‐silicate. Voluminous megacrystic granite intruded early during a mid‐Proterozoic (ca 1000 Ma) granulite event, M₁, widely recognized in east Antarctica. Peak metamorphic conditions for M₁ are in the range of 650–750 MPa at ～800°C and were associated with the development of a gneissic foliation, S₁ and steep east‐plunging lineation, L₁. Strain partitioning during progressive non‐coaxial deformation formed large D₂ granulite facies south‐dipping thrusts, with a steep, east‐plunging lineation. In areas of lower D₂ strain, large‐scale upright, steep east‐plunging fold structures formed synchronously with the D₂ high‐strain zones. Voluminous garnet‐bearing leucogneiss intruded at 940 ±20 Ma and was deformed in the D₂ high‐strain zones. Textural relationships in pelitic rocks show that peak‐M2 assemblages formed during increasing temperatures via reactions such as biotite + sillimanite + quartz ± plagioclase = spinel + cordierite + ilmenite + K‐feldspar + melt. In biotite‐absent rocks, re‐equilibration of deformed M₁ garnet‐sillimanite‐ilmenite assemblages occurred through decompressive reactions of the form, garnet + sillimanite + ilmenite = cordierite + spinel + quartz. Pressure/temperature estimates indicate that peak‐M₂ conditions were 500–600 MPa and 700±50°C. At about 500 Ma, north‐trending granitic dykes intruded and were deformed during D₃‐M₃ at probable upper amphibolite facies conditions. Cooling from peak D₃‐M₃ conditions was associated with the formation of narrow greenschist facies shear zones, and the intrusion of pegmatite. Cross‐cutting all features are abundant north‐south trending alkaline mafic dykes that were emplaced over the interval ca 310–145 Ma, reflecting prolonged intrusive activity. Some of the dykes are associated with steeply dipping faults that may be related to basin formation during Permian times and later extension, synchronous with the formation of the Lambert Graben in the Cretaceous.     

Structural and metamorphic evolution of the Moornambool Metamorphic Complex,western Lachlan Fold Belt,southeastern Australia

The wedge‐shaped Moornambool Metamorphic Complex is bounded by the Coongee Fault to the east and the Moyston Fault to the west. This complex was juxtaposed between stable Delamerian crust to the west and the eastward migrating deformation that occurred in the western Lachlan Fold Belt during the Ordovician and Silurian. The complex comprises Cambrian turbidites and mafic volcanics and is subdivided into a lower greenschist eastern zone and a higher grade amphibolite facies western zone, with sub‐greenschist rocks occurring on either side of the complex. The boundary between the two zones is defined by steeply dipping L‐S tectonites of the Mt Ararat ductile high‐strain zone. Deformation reflects marked structural thickening that produced garnet‐bearing amphibolites followed by exhumation via ductile shearing and brittle faulting. Pressure‐temperature estimates on garnet‐bearing amphibolites in the western zone suggest metamorphic pressures of ～0.7–0.8 GPa and temperatures of ～540–590°C. Metamorphic grade variations suggest that between 15 and 20 km of vertical offset occurs across the east‐dipping Moyston Fault. Bounding fault structures show evidence for early ductile deformation followed by later brittle deformation/reactivation. Ductile deformation within the complex is initially marked by early bedding‐parallel cleavages. Later deformation produced tight to isoclinal D₂ folds and steeply dipping ductile high‐strain zones. The S₂ foliation is the dominant fabric in the complex and is shallowly west‐dipping to flat‐lying in the western zone and steeply west‐dipping in the eastern zone. Peak metamorphism is pre‐ to syn‐D₂. Later ductile deformation reoriented the S₂ foliation, produced S₃ crenulation cleavages across both zones and localised S₄ fabrics. The transition to brittle deformation is defined by the development of east‐ and west‐dipping reverse faults that produce a neutral vergence and not the predominant east‐vergent transport observed throughout the rest of the western Lachlan Fold Belt. Later north‐dipping thrusts overprint these fault structures. The majority of fault transport along ductile and brittle structures occurred prior to the intrusion of the Early Devonian Ararat Granodiorite. Late west‐ and east‐dipping faults represent the final stages of major brittle deformation: these are post plutonism.     

桐柏碰撞造山带及其邻区变形特征与构造格局

桐柏碰撞造山带及其邻区可以划分为九个大地构造单元,自北向南分别是:华北克拉通南缘岩石构造单元——宽坪岩群、具弧后盆地性质的二郎坪岩石构造单元、具岛弧性质的秦岭杂岩单元、龟山岩组和南湾岩组构成的俯冲前缘楔构造带、构造混杂岩带、桐柏北部高压岩片单元、桐柏核部杂岩单元、桐柏南部高压岩片单元以及随州构造变形带。根据详细的构造解析以及新的地质年代学资料,本文将中生代以来的构造变形划分为五幕,前两幕变形主要发育在构造混杂岩带以南的各个岩石构造单元中,之后的三幕变形则波及整个研究区。第一幕变形的时间约为255～238Ma,以发育区域上透入性的片理及北西西向的拉伸线理为主,并导致了高压岩片早期自西向东的挤出。第二幕变形的时间约为230～215Ma,以自北向南的逆冲推覆构造为主,使得高压岩片进一步垂向抬升。第三幕变形应早于下侏罗统,以近北西西向的宽缓褶皱为主要特征,该幕变形期间桐柏核部杂岩及其两侧高压岩片单元发生同步的抬升。第四幕变形大致发生在140～130Ma之间,主要表现为桐柏核部杂岩两侧走滑型韧性剪切带的活动,桐柏核部杂岩表现出向东的挤出。第五幕变形发生在120～80Ma,表现为北西向及北东向的脆性断裂活动,并切割以上所有构造形迹。桐柏高压岩片的抬升剥露受多幕变形控制,呈阶段性的抬升。     

Barry Granodiorite and Sunset Hills Granite: Wyangala‐style intrusion at the margin of a regional ductile shear zone,northern Lachlan Fold Belt,New South Wales

The Barry Granodiorite is a weakly deformed I‐type, and the Sunset Hills Granite is a moderately deformed S‐type, granite. Both granites were passively intruded into an already foliated greywacke and volcanic sequence. Emplacement may have been facilitated by faults related to the oblique opening of the late Early Silurian Hill End Trough. The granites display a dominant foliation which formed during the late Middle Devonian and subsequently was reoriented during the Early Carboniferous. The Barry Granodiorite and Sunset Hills Granite are on the margin of north‐south ductile shear zones related to the Wyangala Batholith. These granites and the adjacent Carcoar Granodiorite have undergone reorientation during movement on ductile shear zones either due to megakinking during late‐stage north‐south shortening, or southeastward movement of the southern margin of the west‐northwest‐trending Lachlan Transverse Zone.     

Using airborne geophysical data in identifying tectonic lineaments in east of Iran

In this paper we tried to identify the main tectonic lineaments in Eastern Iran including Lut block and Sistan suture zone from the airborne geomagnetic data together with tilt filter. As the map of obtained lineaments from airborne geomagnetic data has been studied, four distinct set of lineaments has been identified: (i) north–south, (ii) east–west, (iii) northeast–southwest, and (iv) northwest–southwest that are concurrently with structural zones and area’s big faults. New faults which have been identified in this investigation are lineaments with trend northeast–southwest and east–west. The depth of these lineaments has been calculated through Euler modeling. Magnetic lineaments trending east–west have the most depth, so these lineaments are related to basement faults.     

Thick‐skinned folding in the eastern Lachlan Fold Belt,Shoalhaven River Gorge,New South Wales

In the Shoalhaven River Gorge, in the eastern Lachlan Fold Belt, the Ordovician quartz‐turbidite succession (Adaminaby Group) is affected by one major phase of deformation with northerly trending, gently plunging, upright, close to tight folds (F₁) characterised by a range in half wavelengths up to 3 km. Several anticlinoria and synclinoria are developed and folds occur in at least four orders; these characteristics are consistent with buckling occurring at several scales and are controlled by the thickness of competent units in the multilayered succession. F₁ folding is thick‐skinned in style with the whole crust probably having been affected by deformation. D₁ occurred during the Silurian to Middle Devonian interval and was associated with crustal thickening and the shallowing of depositional environments over time. Locally, F₁ is overprinted by south‐southeast‐trending, steeply to moderately inclined F₂ that reorients F₁ to recumbent attitudes. D₂ is of Early to Middle Carboniferous age. Both deformations are related to convergence in an intra‐arc to backarc region and occurred inboard of a subduction zone, remnants of which occur in the New England Fold Belt.     

Timing of megakinks and related structures: Constraints from the Devonian Bunga‐Wapengo Basin,Mimosa Rocks National Park,New South Wales

The Bunga beds are bounded by faults adjacent to which are fanglomerates that form part of an early Late Devonian volcanic rift basin. Some cross‐faults acted as precursors for later regional deformation that kinked the Ordovician basement and gently folded the basin sediments in a northwest‐southeast direction. Details of the faulted junction at Picnic Point and orientation of cleavage microstructures in the fanglomerates support the dating of the north‐south regional F₂ deformation as Middle Devonian or older and the northwest‐southeast F₃ kinking as post‐early Late Devonian.     

Proterozoic deformation in the east Pilbara Craton and tectonic setting of fault-hosted manganese at the Woodie Woodie mine

Neoarchean and Mesoproterozoic sequences in the Oakover Basin provide a record of deformation and sedimentation along the eastern edge of the Archean Pilbara Craton. The early extensional history of the Oakover Basin is overprinted by subsequent compressional events. Five distinct deformation events are recognised in the Woodie Woodie region; the Archean D₁ event, comprising west-northwest–east-southeast extension associated with formation of the Neoarchean Hamersley Basin; the Mesoproterozoic D_2a event, with northwest–southeast extension and basin formation associated with manganese mineralisation; the D_2b event, with renewed extension associated with intrusion of Davis Dolerite during the ca 1090–1050 Ma Warakurna event; the D₃ event, comprising northeast–southwest-directed compression attributed to the ca 900 Ma Edmundian Orogeny; the Neoproterozoic D₄ event, with east-northeast–west-southwest extension producing large D₄ grabens associated with the opening of the Officer Basin; and, the Neoproterozoic D₅ event comprising north–south-directed compression attributed to the ca 550 Ma Paterson Orogeny. Abundant manganese deposits are hosted by the Neoarchean and Mesoproterozoic sequences in the Oakover Basin, including the large high-grade manganese deposits at Woodie Woodie. The orebodies are predominantly hydrothermal in origin, with a late supergene overprint, and deposition of primary manganese mineralisation was synchronous with northwest–southeast Mesoproterozoic D_2a extension and basin formation. The manganese is associated with normal faults, and many of these represent growth faults related to basin formation. Stratabound manganese is found above or adjacent to fault-hosted manganese. An initial structural framework established during Archean rifting was reactivated in the D_2a event and provided a major structural control on manganese distribution. High-grade manganese deposits at Woodie Woodie mine appear to be located in a zone of oblique dextral extension on major north-northwest- to north-trending faults that mark the eastern ‘active’ or faulted margin of an early rift basin. These large north-northwest-trending normal faults are linked to a major northwest-trending transform fault zone (Jewel-Southwest Fault Zone) that separates the Oakover Basin into a northern and southern basin. The transform fault represents a major deep fluid conduit for hydrothermal fluids and most likely accounts for the concentration of significant manganese occurrences immediately to the north and south of this structure.     

青藏高原东西向伸展及其地质意义

东西和南北向伸展是青藏高原最显著的地质特征之一。南北向伸展形成的东西走向伸展构造,主要包括藏南拆离系(STDS),和沿喀喇昆仑—嘉黎断裂带(KJFZ)发育的正断层体系。东西向伸展形成数目众多的南北走向伸展构造,它们切割青藏高原几乎所有的东西走向构造单元,包括羌塘地块、KJFZ和STDS等,说明东西向伸展以整体形式发生并同时波及整个青藏高原,而不是由以KJFZ和STDS为边界的不同地块的不均匀挤出所致。南北走向伸展构造在地表呈之字形,为南北向挤压形成的追踪张断裂;剖面上表现为被后期高角度正断层叠加的拆离断层,拆离断层形成于中-晚中新世而高角度正断层形成于上新世及以后。导致拆离断层的东西向伸展可能是南北向挤压的变形分解,后期高角度正断层作用可能是高原隆升后的垮塌所致。东西向伸展是控制青藏高原新生代浅色花岗岩和盆地形成的主要因素。     

Structural analysis of the Mystery Bay area,New South Wales

The Ordovician sedimentary rocks of the southeastern Lachlan Fold Belt in the Mystery Bay area are folded into two approximately coaxial and subhorizontally plunging fold series: F₁ and F₂. Regional domains with internally consistent F₁ and F₂ trends are juxtaposed along strike‐slip faults. Locally developed kink bands commonly have a close spatial relationship with the domain boundaries.

A faulted domain boundary is exposed in coastal rocks at Mystery Bay between north‐northeasterly trending turbidites and northwesterly trending complexly deformed cherts and pelites of the Wagonga Beds. South of the boundary fault, F₁ and F₂ trends in the turbidite succession exhibit a segmented 75° counterclockwise rotation about a near‐vertical axis within a 750 m wide zone parallel with the coast, relative to regional trends preserved farther south. The rotation zone hosts prolific subvertical kink bands and crenulations. The turbidite succession youngs towards the east and hence its present position is incompatible with its projected along‐strike position on the western limb of a major anticline exposing the older Wagonga Beds.

At least three generations of faulting are recognized. Within the coastal Wagonga Beds, a set of post‐F₁ faults is subparallel to the tectonic grain and probably had vertical motion. Two systems of post‐F₂ strike‐slip faults include a conjugate system in coastal outcrops, with offsets indicative of layer‐normal shortening; and a series of northerly trending faults, with probable sinistral displacements, recognized from inland exposures.     

Structural history of the Arthur Lineament,northwest Tasmania: An analysis of critical outcrops

The Arthur Lineament of northwestern Tasmania is a Cambrian (510 ± 10 Ma) high‐strain metamorphic belt. In the south it is composed of metasedimentary and mafic meta‐igneous lithologies of the ‘eastern’ Ahrberg Group, Bowry Formation and a high‐strain part of the Oonah Formation. Regionally, the lineament separates the Rocky Cape Group correlates and ‘western’ Ahrberg Group to its west from the relatively low‐strain parts of the Oonah Formation, and the correlated Burnie Formation, to its east. Early folding and thrusting caused emplacement of the allochthonous Bowry Formation, which is interpreted to occur as a fault‐bound slice, towards the eastern margin of the parautochthonous ‘eastern’ Ahrberg Group metasediments. The early stages of formation of the Arthur Lineament involved two folding events. The first deformation (CaD₁) produced a schistose axial‐planar fabric and isoclinal folds synchronous with thrusting. The second deformation (CaD₂) produced a coarser schistosity and tight to isoclinal folds. South‐plunging, north‐south stretching lineations, top to the south shear sense indicators, and south‐verging, downward‐facing folds in the Arthur Lineament suggest south‐directed transport. CaF₁ and CaF₂ were rotated to a north‐south trend in zones of high strain during the CaD₂ event. CaD₃, later in the Cambrian, folded the earlier foliations in the Arthur Lineament and produced west‐dipping steep thrusts, creating the linear expression of the structure.     

Deformation of host rocks and stratiform mineralization in the Hilton Mine area,Mt Isa

The Hilton deposit is a deformed and metamorphosed Proterozoic stratiform Pb‐Zn‐Ag‐Cu deposit hosted by dolomitic and carbonaceous sediments of the Urquhart Shale of the Mt Isa Group. Rocks in the Hilton area show a history of folding and faulting which spans the time range recognized elsewhere in the Western Succession of the Mt Isa Inlier, though the effects of relatively late and brittle deformation are more pronounced in the Hilton area. The Hilton area shows intense faulting relative to similar rocks to the south in the Mt Isa‐Hilton belt. Faulting in the Hilton area has generally resulted in east‐west shortening and extension in both north‐south and vertical directions. This relatively intense late strain is attributed to the geometry of the Paroo Fault Zone, a major north‐trending zone that bounds the Hilton area to the west, and the Sybella Batholith, which formed a relatively rigid indenter during late deformation in the Hilton area. The structural history of the Hilton area is broadly consistent with ongoing east‐west shortening during progressive uplift from mainly ductile to more brittle conditions. Based on these observations, thinning of the Mt Isa Group which was previously attributed to synsedimentary faulting, can now be shown to be related to heterogeneous strain during late faulting. Sulphide layers show a history of folding which is similar to that of the surrounding rocks. Pyrite which is paragenetically associated with mineralization is overprinted by a bedding‐parallel foliation which predates all other structures in the area. This suggests that stratiform sulphide mineralization in the Hilton area predates deformation. Deformation has affected the Hilton orebodies at all scales. Changes in thickness and ‘fault windows’ in the orebody interval occur on the scale of the entire deposit. Mesoscopic ore thickness changes are often clearly related to extensional and contractional structures within sulphide layers. These macroscopic and mesoscopic ore‐thickness variations are spatially associated with cross‐cutting brittle faults, suggesting that strain incompatibility between brittle host rocks and more ductile ore layers played a major role in the present geometry and thickness of sulphide ores at Hilton.     

Large‐scale structures on Gazelle Peninsula,New Britain: Implications for the evolution of the New Britain arc

Geological mapping of fault systems on the Gazelle Peninsula, eastern New Britain arc, combined with a reinterpretation of existing sea floor data indicate that faults previously thought to be a possible location of the boundary between the North and South Bismarck Plates, do not appear to be directly related to the plate boundary spreading centres and transform faults in the 3.5 Ma Manus Basin. Structure on the Gazelle Peninsula is dominated by the Mediva Fault (new name) and the Wide Bay Fault System, both north‐northwest trending, deep‐seated features. The Mediva Fault, an element of the Baining Mountain Horst and Graben Zone, is an extensional structure which has focused Middle Miocene intrusive activity, controlled Mio‐Pliocene sedimentation in the central Gazelle Peninsula, and displaced Quaternary volcanic deposits. The Wide Bay Fault System has been active since at least the Late Oligocene. One hundred kilometres of sinistral strike‐slip motion is likely on this fault since at least the late Middle Miocene, moving the Gazelle Peninsula in a north‐northwest direction with respect to the remainder of New Britain. The nature and timing of movements along these two major structures indicate that some other major tectonic process has operated (and presently continues) in this region of the New Britain arc to create these structures.