bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cainozoic sedimentation in basins adjacent to a major continental transform boundary in southern New Zealand
Authors: Norris R. J. , Carter R. M. , Turnbull I. M. 
Published: December 2007

The Indo-Australian/Pacific plate boundary crosses the New Zealand continental block as the Alpine fault system, an oblique continental transform. Plate tectonic calculations for the SW Pacific imply the inception of this plate boundary in the latest Eocene. In western South Island, rapidly subsiding flysch basins were established at this time. Southeast of the Alpine Fault, basins developed along an active tectonic trend, the Moonlight Tectonic Zone. Early Oligocene infilling by thick submarine fan sequences was accompanied by regional subsidence, so that by late Oligocene, deep marine mudstone was dominant in basins and limestone on adjacent shelf areas. In contrast, early to mid Miocene time was characterized by contemporaneous uplift and subsidence, with tectonic activity on basin margins and development of new source areas adjacent to the Alpine Fault. Reverse faulting, folding and uplift developed at about 12 Ma and continues today.
The sedimentary history is consistent with the development of the plate boundary from a zone of slow oblique extension, to a through-going continental transform, to a compressive transform system. Continental transform boundaries appear to be characterized by small, tectonically active basins, and by a complex tectonic history, particularly when close to the pole of relative rotation. Although difficult to recognise, they may be important in the geologic record.
Metallogenesis in SE Asia
Authors: Hutchison C. S. , Taylor D. 
Published: December 2007

Southeast Asia may be subdivided into three distinct metallogenic provinces— (
a
) peripheral Cenozoic volcanic arc, (
b
) Mesozoic Sundaland core, and (
c
) cratonic China north of the Red River Suture:
a
is a major producer of copper with minor gold and silver;
b
is the World's foremost producer of tin with subordinate tungsten and antimony;
c
is the World's premier tungsten and antimony province, with subordinate tin and mercury.

Ophiolites, obducted since the Palaeocene from Pacific and marginal basin lithosphere, yield substantial chromite, increasing amounts of nickel from residual laterite, and massive Cyprus-type sulphides.
Palaeocene to Miocene dioritic stocks, within the ensimatic arcs of the Philippines and north Sulawesi, contain important porphyry coppers. Gold and silver are important associates, but molybdenum is rare. Kuroko-type sulphides and mesothermal copper-gold vein deposits are important in the Philippines and Taiwan. Epithermal gold-silver telluride vein deposits are more widespread throughout the Cenozoic volcanic arc.

Tin mineralization, spatially related to acid granitoids of Permo–Triassic age in Indonesia and the Malay Peninsula and of Cretaceous age in Phuket and Tenasserim, is widespread in province
b.
Important lode deposits are confined to Billiton and the East Coast Belt of the Peninsula, emplaced within the zone of fracture around high level granitoids. Some stratiform iron-tin deposits characterize this Eastern Belt. Other tin fields, which yield the bulk of the region's production, contain few worthwhile lode deposits. Huge amounts of tin have been produced from the contact zones of large deep-seated batholiths in Bangka, along the Main Range of the Malay Peninsula, and in the Phuket region of Thailand. The tin has been concentrated in Quaternary placers by the favourable combination of climate and topography.

In the Southern Shan States and north Thailand, the deposits are associated with Triassic granites and have yielded more tungsten than tin, as well as significant amounts of antimony. Major tungsten and less important tin deposits are associated with Mesozoic granitoids in the Caledonian foldbelt of southeastern China. The important antimony and mercury occurrences lie on the continental side of the tungsten-tin belt.
Gold, antimony and mercury mineralization is associated with Tertiary igneous rocks in West Borneo, and mercury occurs in Palawan island.
Iron contact-metasomatic and sedimentary ore deposits are associated with the Mesozoic igneous rocks in China and Sundaland, and with Cenozoic dioritic rocks in the Philippines.
The metallogenic zonation of China may be related to subduction of oceanic material beneath a continental margin, persistent since the early Mesozoic. In SE Asia, more complex patterns of subduction have resulted in less well defined metal zonation in the continental regions. Cenozoic mineralization in the Philippines and Indonesia resulted from convergent tectonics of great complexity involving both continental and oceanic crust of diverse origins.
Geochemical evolution in an advancing, periodically replenished, periodically tapped, continuously fractionated magma chamber
Authors: O’Hara M. J. , Mathews R. E. 
Published: December 2007

A summary of the development of ideas concerning geochemical evolution in periodically replenished, periodically tapped, continuously fractionated magma chambers lists 28 main conclusions or observations. The main body of the paper presents the derivations of the relationships which underpin these conclusions and lead on to a further 10 observations about the likely behaviour of such systems.
If periodically replenished, periodically tapped, continuously fractionated magma chambers exist, they will evolve products whose phase petrology and trace element chemistry appear (in hitherto conventional interpretations) to require variable degrees of partial melting of in homogeneous source regions for their petrogenesis. When the additional effects arising from assimilation by the magma of the roof of the chamber and from variation of mineralogy at the solidus of even a chemically homogeneous peridotite mantle are added, the scope for confusion is greatly increased. Moreover, these relationships cannot be inverted in order to deduce uniquely the magma chamber parameters or mantle source compositions from a knowledge of the erupted products. Available evidence suggests that interpretation of many igneous provinces, especially that of the mid-ocean ridges, will be complicated by these considerations.
The geology of the Kuh-e Dalneshin area of southern Iran, and its bearing on the evolution of southern Tethys
Authors: Stoneley R. 
Published: December 2007

The Kuh-e Dalneshin area lay close to the northern margin of the Arabian continent during Mesozoic and Palaeogene times. Recent mapping has shown that, except perhaps in the late Cretaceous, it was inactive until it collided with Central Iran in the Miocene: the collision, represented by a Neogene mélange zone in the NE, resulted in the Zagros orogeny, and is expressed in the shelf sediments by folding, parallel faulting and a possible arcuate sinistral shear.
In the late Cretaceous, a localized deepening of the shelf dates from the Cenomanian. A narrow trough in the W subsided to abyssal depths in the Turonian. Following a period of faulting, a more wide spread subsidence affected the shelf in the Coniacian and Santonian: autochthonous cherts and associated sediments accumulated. Basaltic volcanics were erupted in the NE part of this basin, and Permian to Cenomanian neritic exotic blocks were derived presumably from an uplift at the shelf edge. The rocks from the outer edge of this basin slid westwards over their autochthonous counterparts, probably in the Campanian, accompanied by further gliding of masses of earlier Mesozoic cherts, which had previously been emplaced on the continental margin. A sheet of mantle peridotite, partly serpentinized and enclosing neritic and metamorphic exotics, in turn slid into the basin. Shelf sedimentation was renewed in the late Campanian or Maestrichtian, but the transgression did not reach the area until the Eocene.
The derivation and emplacement of the allochthonous rocks in the late Cretaceous are still imperfectly understood: alternative models are discussed, one involving gliding from an aborted spreading ridge along the continental margin, the other more conventionally based on subduction processes. A preference is expressed for the former.
Depositional history of the late Pleistocene limestones of the Kenya coast
Authors: Braithwaite C. J. R. 
Published: December 2007

The coastal limestones of Kenya extend approximately 180 km N-S from Malindi to the Tanzanian border. They are at least 20 m thick and may be subdivided into sedimentary units representing major periods of marine deposition punctuated by sub-aerial erosion.
Their foundations are formed by thick fluvial and aeolian quartz sands but there is local evidence of marine deposition following these. In the main limestone unit, deposited about 240,000 years ago, initial high energy shallow-shelf deposition was replaced by quiet water sediments with scattered corals. Sea level stood about 8 m higher than at present. Quartzose sands were confined to western areas.
A return to shallow water heralded a new phase of emergence and erosion, producing karst surfaces and sub-aerial sediments. These are overlain by herring-bone cross-bedded quartz-rich calcarenites which were the products of a tidally dominated shelf and, at Watamu and Wasini, pass upwards into aeolian dune deposits. However, these were also emersed and subject to karst erosion before deposition of a further widespread marine limestone. Within this, coral knolls are well developed. Much of the sediment accumulated in shallow water, but the ecological succession indicates that knolls were at times in deeper waters. These deposits formed about 125,000 years ago when sea level ultimately stood 15–20 m above its present position.
More recently in the area sea level has again fallen. However, the descent was not continuous and pauses were marked by marine terrace formation and subsequent karst erosion with sub-aerial deposition. Brief reversals caused both terraces and sediments to be overlain by thin marine deposits. Sea level paused at its present position about 30,000 years ago when the present reef platform was probably defined. It continued to fall to a maximum of about-120 m before rising to its existing level 7000 years ago and beginning the current cycle of sediment accumulation.
A coal depositional model for the Durham Coal Measures of NE England
Authors: Fielding C. R. 
Published: December 2007

The Upper Carboniferous (Westphalian) Coal Measures of the Durham coalfield were deposited on a broad, flat, deltaic plain. In early Westphalian A times, a lower delta plain setting prevailed, evolving through southward deltaic progradation into an upper delta plain by mid-Westphalian A.
Detailed facies analysis of large, opencast exposures, supported by extensive subsurface data, has shown that a hierarchy of depositional controls operated across the Durham area during Westphalian times; (i) on the large scale, depositional geometry was controlled by patterns of major delta progradation and switching; (ii) on the medium scale, by a combination of structurally and compactionally induced subsidence, and (iii) on the small scale, by local sedimentary processes and subsidence patterns.
These observations form the basis of a coal depositional model for the Durham Coal Measures, which predicts that the thickest coals are to be found in upper delta plain domains controlled by compactional subsidence and not underlain by substantial channel sandstones. This model may also be applicable to other coalfields of northern England, and to ancient delta plain sequences elsewhere in the world.
U-Pb zircon geochronology and geological evolution of the Halaban-Al Amar region of the Eastern Arabian Shield, Kingdom of Saudi Arabia
Authors: Stacey J. S. , Stoeser D. B. , Greenwood W. R. , Fischer L. B. 
Published: December 2007

U-Pb zircon model ages for eleven major units from the Halaban-Al Amar region of the eastern Arabian Shield indicate three stages of evolution: (1) plate convergence, (2) plate collision, and (3) post-orogenic intracratonic activity.
Convergence occurred between the western Afif and eastern Ar Rayn plates that were separated by oceanic crust. Remnants of oceanic crust now comprise the ophiolitic complexes of the Urd group. The oldest plutonic unit in the study is from one of these complexes and gave an age of 694 ± 8 Ma. Detrital zircons from the sedimentary Abt formation of the Urd group, which is intercalated with the ophiolitic rocks, were derived from source rocks with a mean age of 710 Ma. The Abt formation may be an accretionary wedge on the western margin of the Ar Rayn plate. Plate convergence was terminated by collision of the Afif and Ar Rayn plates during the Al Amar orogeny which began about 670 Ma. During collision, the Urd group rocks were deformed and in part obducted on to one or both plates. Synorogenic leucogranitoid rocks were intruded from 670 to 640 Ma. From about 640 to 630 Ma, widespread unfoliated dioritic plutons were emplaced in the Ar Rayn block, and represent the end of orogenesis related to collision. There is no definitive evidence for a significantly older basement beneath the study region.
Pressures and temperatures of metamorphism in the eastern Dalradian
Authors: Baker A. J. 
Published: December 2007

Pressures and temperatures have been determined from locations in the eastern Dalradian using a number of different geothermometers and geobarometers. Temperatures range from 550°C in the low kyanite zone to about 800°C in the sillimanite–K feldspar zone. Pressures range from about 5.5 kbar in Glen Esk to 9–10 kbar in the Central Highlands. The barometric calibrations employed are consistent with the kyanite–sillimanite equilibrium.
Evidence from mineral zoning suggests that rocks outside the Buchan area (in the Duchray Hill Gneiss, Glens Clova and Avon and in the Schichallion area) underwent a pressure decrease synchronous with the metamorphic peak.
Regional temperature variations define a thermal high centred on the Cromar–Glen Muick–Duchray Hill Gneiss area. To the W of this high temperatures decrease rapidly. A sharp thermal break occurs between high grade sillimanite–K feldspar gneisses in Glen Muick and kyanite–staurolite schists to the W. This thermal contrast is attributed to a structural break which may be analogous to a number of other thermal features in the Dalradian.
The use of cluster analysis in the study of some non-marine bivalvia from the Westphalian D of the Sydney Coalfield, Nova Scotia, Canada
Authors: Vasey G. M. , Bowes G. E. 
Published: December 2007

Cluster analysis is combined with Principal Components Analysis in an attempt to study the variation in shell-shape displayed by non-marine bivalves of the genusAnthraconautapruvost from the Sydney coalfield, Nova Scotia. Two assemblages of shells, 89 from above the Phalen seam and 91 from between the Harbour and Hub seams of the Westphalian D, are analysed.The method requires the measurement of only six linear shell dimensions in order to produce a phenetic classification. The results are presented in the form of phenograms, stereo Principal Component plots and pictographs. Use of Principal Components Analysis allows the construction of reproducible pictographs with identified variational trends.A new morphospecies,Anthraconauta calveri, is figured and described as a result of the analyses which are found to be broadly in agreement with the Trueman & Weir system of nomenclature presently in use for the classification of Upper Carboniferous non-marine bivalvia. Suggestions are made as to how this system of nomenclature might ultimately be modernized and revised
The Structure of the West Orkney Basin, northern Scotland
Authors: ENFIELD M. A. , COWARD M. P. 
Published: December 2007

The West Orkney Basin developed in Devonian times, as the western part of the Orcadian intermontane basin. It has been studied using commercial speculative seismic reflection data and the MOIST deep seismic data. The NW edge of the West Orkney Basin is formed by listric faults which are also strongly arcuate in plan, while the SE part is composed of straight domino-type faults which formed parallel to earlier (Caledonian) layering in the basement. Fault restoration and balancing suggest that initial extension in the basin occurred on low-angle reactivated Caledonian thrust faults. Steeper breaching faults cut the low-angle set, forming planar (domino-type) faults in the centre of the basin but listric faults at the NW margin. The maximum extension is about 45% in the basin centre, most of this being taken up on the later breaching fault system. This extension decreases to the SW, where fault tips occur on-shore, but some may transfer to fault systems in the Minches. The faults apparently decouple at a depth of 18-20 km and the extension suggests an initial post-Caledonian crustal thickness of up to 40 km. However, the sedimentary thickness is an average of only 3 km in the basin centre, much less than would be expected had the lithosphere thinned homogeneously, and there is no evidence of a thermal subsidence phase to the basin. This suggests that the extension shown by the West Orkney Basin was transferred to lower lithospheric levels to the east along the deep decoupling zone.
The Devonian sediments on-land show facies changes and periods of uplift and erosion which may be related to extension during basin development. They also show a phase of pre-Late-Permian tectonic inversion where the beds are locally folded and thrusted, probably related to the Hercynian events further south. The West Orkney Basin is capped by Mesozoic sediments and was probably reactivated during Mesozoic basin development in the Minches and Moray Firth.
The shape of the faults, their orientation and decoupling levels are strongly controlled by the earlier Caledonian structure, in particular by the layering and crustal anisotropy developed along and above the Moine thrust. The West Orkney Basin with its 20 km deep decoupling level formed by extension of Caledonian thickened crust. It is notable that the major basin-bounding faults to the NW, the Outer Isles and Flannan faults, which developed where the crust was thinner and hence less ductile at depth, decoupled at much deeper structural levels, at the Moho or below.
Structural evolution of Mesozoic Peninsular Malaysia
Authors: HARBURY N. A. , JONES M. E. , AUDLEY–CHARLES M. G. , METCALFE I. , MOHAMED K. R. 
Published: December 2007

Field evidence from Upper Palaeozoic and Mesozoic strata exposed in Peninsular Malaysia demonstrates that the structural style, degree and orientation of folding, axial-plane cleavage, and faulting in the Triassic, Jurassic and Cretaceous rocks of the central basin are remarkably similar. In contrast, the Upper Palaeozoic strata, especially the Carboniferous rocks exposed in the eastern part of the peninsula, show multiple phase folding and regional metamorphism unlike anything seen in the Mesozoic rocks. These observations demonstrate that two important compressional events affected Peninsular Malaysia, one in Late Permian times and the other in the mid- to late Cretaceous. The Late Palaeozoic compressional event was a major orogenic mountain building phase with associated emplacement of major Permo–Triassic granite plutons that form the eastern and main ranges. No indications were found of the widely reported Triassic orogenic compression. The palaeotectonic and palaeogeographical implications of these discoveries are important for interpreting the evolution of eastern Gondwana and Tethys.
The Raub–Bentong line was an important fault zone active during the Mesozoic but does not appear to have been a major tectonic suture since the Late Palaeozoic. We postulate that the Permo–Triassic granites of the eastern belt and those presently exposed in the main range were originally about 30–50 km apart, and that Triassic and Jurassic crustal attenuation and subsidence led to the separation of these two granitic belts by more than 100 km.
Sedimentology, geochronology and provenance of the Proterozoic Itremo Group, central Madagascar, and implications for pre-Gondwana palaeogeography
Authors: COX RÓNADH , ARMSTRONG RICHARD A. , ASHWAL LEWIS D. 
Published: December 2007

Proterozoic metasediments of the Itremo Group in central Madagascar probably represent a passive margin sequence predating Gondwana assembly. The quartzites are well-sorted quartz arenites that contain flat lamination, wave ripples, current ripple cross-lamination, and dune cross bedding. The carbonate rocks preserve abundant stromatolites and algal laminates. A continental source is indicated by mudrock major and trace element chemistry. The combination of lithologic association, sediment architecture and mudrock chemistry indicates that the sequence was deposited on a continental shelf or platform.SHRIMP data from detrital zircons indicate that the source area included early Proterozoic and late Archean rocks with ages between 1.85 and 2.69 Ga, and that the depositional age of the Itremo Group must be less than 1855 ± 11 Ma. The sequence has been deformed into a series of large-scale folds separated by ductile shear zones. SHRIMP data indicate both massive lead loss from detrital zircons and new zircon growth in the metasediments at 833 ± 112 Ma, which we interpret as the age of metamorphism of the sequence. Comparison of detrital grain ages with basement ages in East Africa and in India indicates that the source area for the Itremo Group probably lay on the present African mainland.
Central subsidence in the layered Hypersthene-gabbro of Centre II, Ardnamurchan, Argyllshire
Authors: Skelhorn Raymond Richard , Elwell Royston William Dunlop 
Published: December 2007

Summary
The layering in the Hypersthene-gabbro of Centre II, Ardnamurchan has been mapped in as much detail as possible. The dips are confocal and steepen inwards, up to more than 50°, towards a central area occupied by later intrusions. The pattern of confocal dips is incomplete, partly because the eastern half of the gabbro has been cut out by Centre III intrusions and partly because the gabbro is not rhythmically layered throughout. There is convincing evidence that the layering was produced by bottom accumulation on successive floors which were more or less horizontal, so that the inward steepening must be due to later deformation. It is considered that the deformation concerned represents a downbending produced by movement on a ring fault, which is now obliterated. This process of cauldron subsidence dropped the central part of the gabbro to a lower level and permitted the emplacement of the next intrusion in the Centre II sequence, the granophyric quartz-dolerite. From a survey of the literature it would appear that there are other gabbros for which the attitude of the layering shows a pattern which we think may have been produced by cauldron subsidence.
A Precambrian conglomerate with an amphibolite matrix near Kaladar, Ontario
Authors: van de Kamp Peter Cornelis 
Published: December 2007

Summary
The mineralogy and chemistry of the amphibolitic matrix of a metamorphosed Precambrian conglomerate throw light on the derivation of the deposit from eroded basic and acid igneous parent rocks. Chemical analyses for 31 elements in 25 samples illustrate the mafic nature of the conglomerate matrix and show the influence of both basic and acid source types. Indicative of basic source rocks are high Mg, Fe, Cr, Ni, and low Si. Acid rock contributions are recognized by high K and Rb (present in K-feldspar and biotite).
The conglomerate is a peculiar type of metasedimentary amphibolite quite unlike ‘normal’ hornblende-plagioclase amphibolites of meta-igneous origin or the para-amphibolites from Ontario and Scotland previously described. It does not however have a unique composition amongst coarse clastic rocks and similar examples from other locations are cited. Such clastic rocks are probably all first cycle alluvial or fluvial deposits from source areas rich in mafic rocks.