bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase-controlled molecular fractionations in migrating petroleum charges
Authors: Larter Stephen , Mills Nigel 
Published: April 2008

Abstract
An experimental approach has been used to make a preliminary examination of the possible effects of partitioning processes distributing molecular markers between vapour and liquid petroleum phases during petroleum migration in the system gas-saturated oil/condensate-saturated gas. These effects are discussed with reference to several traditional petroleum geochemical parameters. Some source and maturity related geochemical parameters are dispersed from the inherited source values when a petroleum system undergoes a transition from a single phase gas-condensate to a two phase system and it is probable that partitioning is one of the many processes that contribute to the scattered data sets observed in natural systems particularly those associated with gas/condensates.
In addition to affecting gross composition and gas and gasoline range composition, physical partitioning of petroleum components between vapour and liquid phases in deep reservoirs containing rich gas condensate vapour and a liquid petroleum phase in equilibrium can affect even high molecular weight components, selectively partitioning lower homologues into the vapour phase. This may disperse to various degrees any source inherited signature in source facies or maturity interpreted from parameters such as aromatic hydrocarbon distribution, gasoline range parameters, or sterane carbon number distribution.
Migration history, or the frequency and extent of multiple equilibrations between vapour and liquid phases in deep high pressure reservoirs followed by selective release of one phase to a shallower position to produce a two phase petroleum system is proposed as an important variable in the geochemical interpretation of once equilibrated petroleum systems. It is concluded that phase related effects must be considered in addition to accepted source and maturity considerations as controlling the molecular composition of two-phase petroleums derived from single-phase precursors. This is particularly so for rich gas condensate systems.
A case study of migration from the West Canada Basin
Authors: Piggott N. , Lines M. D. 
Published: April 2008

Abstract
A regional model for hydrocarbon charge in the West Canada Basin is presented. Three discrete ‘hydrocarbon cells’: Devonian, Mississippian-Neocomian and mid Upper Cretaceous (Post-Mannville) host petroleum which was indigenously generated from five major source rocks. Source depositional environment and Columbian-Laramide basin geometry control this pattern. On a regional scale, lateral carrier bed migration dominates basin plumbing, with the mid Cretaceous Mannville Group (oil sands) acting as the ultimate gathering point for subcropping source-carrier systems.
At a play-specific level, an example of significant local vertical migration within the gas phase is presented to explain charge of Permo-Carboniferous sands in the Peace River Arch area.
The northern Oman Tethyan continental margin: stratigraphy, structure, concepts and controversies
Authors: Robertson A. H. F. , Searle M. P. 
Published: April 2008

Abstract

The Oman Mountains constitute one of the best areas in which to study the development and subsequent deformation of a passive continental margin. Pulsed rifting of the Arabian craton in Early and Late Permian time was followed by Middle to Late Triassic sea-floor spreading and opening of the Tethys ocean. Passive margin subsidence continued throughout the Jurassic and Early Cretaceous, interrupted by a pulse of crustal extension in Late Jurassic (Tithonian) time. The Semail ophiolite was generated during the Cenomanian (
c.
95–98 Ma), probably above a newly initiated intra-oceanic subduction zone. Mesozoic Tethyan oceanic crust was later consumed in an oceanward- (northeast-ward)-dipping subduction zone. The essential driving force was the attempted subduction of the Tethyan continental margin. Progressive collision led, in turn to the development of a peripheral bulge and foreland basin (
c.
90 Ma), thrusting and eventual emplacement of the ophiolite onto the margin during late Campanian-Maastrichtian time. Thin-skinned thrust tectonics dominate the entire northern Oman continental margin, with late-stage deeper level thrusting affecting shelf edge and platform carbonates. The basal detachment extends down into deeper levels in the pre-Permian basement in the Musandam Peninsula in the north, and the Jebel Akhdar and Saih Hatat windows further south. During the Early Tertiary, continuing convergence was accommodated along the opposing Makran active margin, while a relatively stable platform was restored in the Oman Mountains area. Renewed compression during the mid-Tertiary, related to continental collision in the Zagros Mountains to the northwest resulted in short distance thrusting further onto the foreland in the northern Oman Mountains. The whole area currently lies within a zone of diachronous continental collision between the African and Eurasian plates.
Sedimentary and structural evolution of a continental margin transform lineament: the Hatta Zone, Northern Oman Mountains
Authors: Robertson A. H. F. , Kemp A. E. S. , Rex D. C. , Blome C. D. 
Published: April 2008

Abstract

The Hatta Zone, Northern Oman Mountains, is interpreted as a
c.
50 km long left-lateral offset of the North Oman passive continental margin that was generated by right-lateral transform faulting during spreading of the Neo-Tethys ocean. During Early-Late Triassic time, slumps, debris flows and calciturbidites composed of redeposited upper slope and shelf carbonates accumulated at the base of a steep carbonate platform slope (Maqam Fm., Mayhah Fm.; Sumeini Group). Clasts in channelized conglomerates include basement-derived quartzose sandstone, schist and basic extrusives. Basaltic pillow lavas were erupted at the foot of the Late Triassic continental rise of the Hatta Zone transform lineament (Zulla Fm.). During Early to mid Jurassic time, oolitic and lithoclastic calciturbidites and debris flows accumulated on tectonically unstable base of slope (Mayhah Fm.) and continental rise (Guweyza Limestone Fm.) settings. During mid-Cretaceous time (Albian-Cenomanian), alkaline magmatism constructed seamounts along the inferred oceanward extension of the Hatta transform lineament. K/Ar ages of diabase sills range from 109 Ma ± 4 Ma, to 105 Ma ± 3 Ma on sills, while basalts gave ages of 104 Ma ± 4, to 93 Ma ± 4. During the Late Cretaceous ophiolite emplacement, abyssal plain and base of slope units were deformed into a major transverse culmination (Jebel Quimah), mainly controlled by collision with the Hatta Zone continental margin transform lineament. Hanging wall imbrication and overturning of structurally high thrust sheets occurred above an inferred footwall ramp. As the Semail ophiolite overrode a northfacing transform escarpment margin, footwall slope sediments were sheared and deformed into a major lateral ramp, now represented by the Jebel Raudha-Masfut ridge. Normal faulting and deep erosion ensued, followed by Maastrichtian-early Tertiary shallow marine carbonate deposition on an unstable shelf. During renewed, mid-Tertiary deformation the Hatta Zone was reactivated, giving rise to NW-SE trending open-folding at right angles to the regional W-directed compression, followed by differential erosion to form the present lineament.
The tectonic evolution of pre-Permian rocks, Central and Southeastern Oman Mountains
Authors: Mann A. , Hanna S. S. 
Published: April 2008

Abstract
The structural history of pre-Permian basement rocks exposed in the domal uplifts of Jebel Akhdar, Jebel Nakhl and Saih Hatat, central and southeastern Oman mountains, is dominated by Late Palaeozoic and Late Cretaceous deformation and metamorphism. In Jebel Akhdar pre-Permian rocks have been deformed by large NE-SW trending thrusts and folds and intense cleavage during Late Palaeozoic compression. Later reactivation of these structures accompanied by a major flattening deformation caused by loading may be related to thrusting and folding in the overlying Permian to Cenomanian platform carbonates. These structures are ascribed partly to Late Cretaceous deformation. The complex internal structure of Saih Hatat is attributed to overprinting of possible Proterozoroic and Late Palaeozoic tectonic events by Late Cretaceous thrusting, folding and associated blueschist metamorphism. The identification of a major basement-cover duplex involving pre-Permian rocks and platform carbonates in Saih Hatat suggests that the pre-Permian basement and platform carbonates did not remain as autochthonous units during Late Cretaceous deformation. Instead, both basement and cover have been thrust southwards during emplacement of the Tethyan thrust sheets onto the Arabian continental margin. Sedimentological evidence from the Tertiary sequence reinforces the development of the Saih Hatat dome as a Late Cretaceous culmination above a deep seated thrust which may have been rejuvenated during the Tertiary. In Jebels Akhdar and Nakhl there is no evidence of a basement-cover duplex. Nevertheless, reactivation of pre-Permian structures and imbrication of cover rocks (Mesozoic platform carbonates) in Jebel Akhdar has important implications to the timing of its structural growth. An alternative model of under-thrusting of the N Arabian margin beneath a subduction trench is also proposed to explain the formation and subsequent elevation of the Oman blueschists.
The interpretation of gravity data in Oman: constraints on the ophiolite emplacement mechanism
Authors: Shelton A. W. 
Published: April 2008

Abstract

The results of the gravity survey which was carried out as part of the Open University Oman Research Project and briefly reported by Lippard
et al.
are presented in detail to further constrain the emplacement mechanism of the Semail Ophiolite. The principal conclusions of the gravity (and magnetic) study are that (i) the Semail Ophiolite nappe continues for a limited distance under the Batinah coastal plain and appears to have a smoothly tapering ‘trailing edge’; (ii) the lower surface of the nappe is approximately planar; (iii) the ‘leading edge’ of the nappe comprises slices some 20% of the thickness of the block to which they are attached; (iv) beneath the coastal plain, to the east of the Hawasina Window culmination, a completely unexposed ophiolite block exists. These conclusions favour the gravity-driven emplacement of the ophiolite nappe of Oman.
The influence of hydrography, bathymetry and productivity on sediment type and composition of the Oman Margin and in the Northwest Arabian Sea
Authors: Shimmield G. B. , Price N. B. , Pedersen T. F. 
Published: April 2008

Abstract
The hydrography, bathymetry and sediment composition of the Oman Margin and NW Indian Ocean areas between latitudes 24°N and 13°N, have been studied. A pronounced oxygen minimum zone characterizes the water column between 200 and 1500 m depth and extends throughout the NW arabian Sea. The bathymetry of the margin is complex, resulting from tectonic movement along the Masirah Line. Small, anoxic intrashelf basins are developed south of Masirah. The Owen/Murray Ridge provides a barrier to westward progradation of terrigenous detritus from the Indus Fan. Upwelling and surface productivity result in the deposition of biogenic calcareous and siliceous sediments, the latter being restricted to the shelf and slope regions. Depositional controls, such as redistribution by bottom currents and bathymetry, greatly affect the quality of organic carbon deposited. Evidence is presented to suggest that much of the organic matter on the Oman shelf is degraded prior to burial. This has important connotations for sediment diagenesis and hydrocarbon maturation. The distribution of calcareous and siliceous sediments resulting from upwelling may well provide an index for determining the Neogene history of upwelling in the NW Arabian Sea.
The volcano-tectonic setting of oceanic lithosphere generation
Authors: Searle R. C. 
Published: April 2008

AbstractThe past two decades have seen a revolution in our knowledge of the detailed structure, tectonic and volcanic patterns of mid-ocean ridge spreading centres and transform faults, brought about mainly by the use of a variety of high-resolution sonars. This paper reviews those studies, and attempts to provide an up-to-date description of those aspects of mid-ocean ridge structure that are most relevant for comparison with ophiolites.
Quaternary marginal basin volcanism in the Bransfield Strait as a modern analogue of the southern Chilean ophiolites
Authors: Keller Randall A. , Fisk Martin R. 
Published: April 2008

Abstract
The Bransfield Strait is an actively-spreading, 65 km wide, Quaternary marginal basin at the northern tip of the Antarctic Peninsula. Across the Drake Passage from the Bransfield Strait are the Tortuga and Sarmiento ophiolites of southern Chile, which have been interpreted as uplifted, Jurassic-Cretaceous, marginal-basin curst that formed in a setting similar to the present Bransfield Strait. We present a comparison between the Bransfield Strait and the Chilean ophiolites, emphasizing new petrological and geochemical data for volcanic rocks dredged from two seamounts at the Bransfield Strait rift axis and published analyses of volcanic rocks from the marginal basin now preserved as the Chilean ophiolites.
Volcanic rocks from the seamounts are about 100 000 years old, and major element abundances in these rocks are broadly similar to enriched mid-ocean ridge basalt (E-MORB). The rocks are slightly enriched in light rare earth elements (LREE) relative to heavy rare earth elements (HREE), as in E-MORB, but they are moderately enriched in alkali, and alkali earth elements, as in arc basalts, and concentrations and ratios of diagnostic trace elements show island arc affinities. Geochemical discrimination diagrams suggest that Bransfield Strait lavas represent the initial stages of a petrogenetic transition linked to the tectonic transition from rifting in an ensialic arc to rifting in a marginal basin.
Published rare earth element data from dykes and lavas in the Chilean ophiolites range from mildey depleted in LREE in the Tortuga ophiolite (Ce/Yb = 0.5 to 0.8, normalized to chondrites) to mildly enriched in LREE in the Sarmiento ophiolite (normalized Ce/Yb = 1.6 to 2.5). The latter are strikingly similar to data from the seamounts in the Bransfield Strait both in LREE enrichment (normalized Ce/Yb = 2 to 2.5) and total REE concentrations (20–45 times chondrite). We believe these chemical similarities, as well as other geological similarities pointed out by other authors, suggest that the Bransfield Strait marginal basin is at the same stage of development as was the marginal basin now preserved as the Sarmiento ophiolite.
Deformation styles adjacent to transform faults: evidence from the Troodos ophiolite, Cyprus
Authors: Allerton Simon , Vine F. J. 
Published: April 2008

Abstract
In the southeast part of the Troodos ophiolite much of the tectonic fabric is demonstrably associated with its formation at a spreading ridge adjacent to the Southern Troodos Transform Fault. A combined palaeomagnetic and structural study has revealed many features of its genesis. Palaeomagnetism can be used to identify original dyke intrusion directions and any subsequent block rotations. The region can be subdivided into two distinct sub-areas on the basis of their dyke orientations. In the southeast corner of the ophiolite, dykes had an original northwest strike, and have suffered only simple tilting about strike-parallel normal faults to assume their present orientation. In contrast, further west, dykes now striking northeast or east have been rotated on average 100° clockwise on sets of strike-slip faults, from an original northwest strike.
A model for the structural processes active at ridge-transform intersections is suggested. Normal faulting dominates at the outside corner, where there is no slip across the transform. At the inside corner, oblique normal/strike-slip faulting is prevalent. Within this context, the eastern area of the ophiolite developed at the outside corner, and the area further west, at the inside corner. A ridge-jump boundary has been preserved between the areas, where a new ridge, which subsequently formed the eastern area, cut the older, western area.
Conodont colour maturation indices for the Carboniferous of west-central Scotland
Authors: Dean Mark T. 
Published: April 2008

Abstract
The colour alteration of conodont elements from Carboniferous samples from west-central Scotland is summarized, and most values fall within indices 1 to 1.5. This range corresponds to geothermal temperatures of <50°C to 90°C which lie within the immature (early dry gas) to mature (perhaps mid-oil window) stages of hydrocarbon generation. Where the index values are 1.5, and other necessary geological criteria are satisfied, support is offered here for oil generation through burial maturation.
Carboniferous source rocks of the Canadian Atlantic margin
Authors: Mossman David J. 
Published: April 2008

AbstractCarboniferous source rocks of relatively low to moderate maturity occur onshore along the Canadian Atlantic margin in Palaeozoic basins of western Newfoundland, New Brunswick and Nova Scotia. Coals of predominantly Westphalian age are widespread and locally abundant. In the Devono-Carboniferous Albert Formation of New Brunswick, and in equivalent Horton Group strata elsewhere in the Maritimes Basin, oil-prone type-I kerogen is predominant.Throughout the Canadian Appalachians, the similarity of Carboniferous strata in various sedimentary basins has facilitated the recognition of four major stratigraphic cycles of deposition. Bounded in nearly every instance by unconformities, these cycles are likewise recognized offshore, where in some cases they have been the focus of commercial investigation. In the Gulf of St. Lawrence region, hydrocarbon-generating potential was early confirmed by drilling in rocks of the Windsor and Canso-Riversdale sequences. These strata may extend north from the Magdalen Basin into the Anticosti Basin, northwestward into the St. Lawrence estuary, and northeast of western Newfoundland.Carboniferous sections south and east of Newfoundland are in most cases strongly overmature. However, recognition of equivalent Horton Group strata within the oil window in a Grand Banks well indicates the potential of Upper Palaeozoic strata to contribute to the accumulation of oil, not only within the Palaeozoic section, but also in younger strata.
Dynamic stratigraphy of the Triassic and Jurassic of the Hebrides Basin, NW Scotland
Authors: Morton Nicol 
Published: April 2008

Abstract
The evolution of the Hebrides Basin during the late Triassic and Jurassic has been established by integrating analyses of subsidence history, sequence stratigraphy and stratigraphical architecture. Two episodes of three-phase evolution occurred from extension-related variable sequences (1A, late Triassic to early Sinemurian; 2A, latest Toarcian to late Bajocian), through sag-related laterally more uniform sequences (1B, mid-Sinemurian to earliest Toarcian; 2B, late Bajocian to late Bathonian), to stabilization—related condensed sequences (1C, Toarcian; 2C, late Bathonian to Callovian). A final third episode of subsidence in Oxfordian to early Kimmeridgian was followed by partial basin inversion in latest Jurasic or early Cretaceous, which caused faulting, tilting and uplift of basement ridges. These structures are unconformably overlain by Upper Cretaceous sediments and Palaeocene volcanics.
There was a single Hebrides Basin during the late Triassic and Jurassic subsiding as a half-graben bounded on the west by the Minch Fault. The intrabasinal Camasunary and related faults are demonstrated not to have been significant tectonic features during the Jurassic. Occasionally they were slightly active but they did not divide the area into two sub-basins. They are largely post-Jurassic. There is evidence of a less strongly subsiding central Skye block, apparently in the area of the later Palaeocene plutonic centre.
The origin of Upper Palaeozoic sedimentary basins in Northern Ireland and relationships with the Canadian Maritime Provinces
Authors: Mitchell W. I. 
Published: April 2008

Abstract
The evolution of Carboniferous and early Permian sedimentary basins in Northern Ireland is related to a rapidly changing pattern of tectonic episodes. Characteristic sedimentary assemblages and facies changes are associated with discrete phases of basin formation and were related to tectonic events that can be correlated with events in a wide zone of dextral strike-slip in the Canadian Maritime Provinces. Small, localized non-marine basins developed during late Asbian-early Brigantian and Westphalian B times. These data support the extension of the Canadian Maritime transform fault system into Northern Ireland in late Silesian times.
Recent developments on the classification of mineral reserves and resources
Authors: Schaffalitzky C. 
Published: April 2008

Abstract
The Institution of Mining and Metallurgy (IMM) and the Irish Association for Economic Geology (IAEG) have felt for a long time that the absence of usable definitions, particularly in ‘the City’ was bringing the minerals industry into disrepute. The IMM has now addressed this problem and has published draft proposals to be presented to the membership. This paper presents a brief personal review of these proposals and suggestions for further improvements.
Assaying in resource evaluation: the need for a clear and open mind
Authors: Sawyer J. B. P. 
Published: April 2008

Abstract
This paper is concerned mainly with assaying of precious and noble metals, gold, silver, and platinum group metals.
The determination of the amount of saleable metals (or other mineral products), in an ore is the most important step in evaluation of a mineral deposit. Most assays, even if well done, will not tell you how the material occurs in the rock or how much of it can be recovered, but if the amount that is present in the first place is unknown, it is impossible to make any comment as to the efficiency of a recovery system. This may not be important because if a recovery can be made which will provide a large profit, that which is not recovered will not seriously affect the economics of the operation. However, where the grade, and thus the operation is marginal, this is a different matter.
Fire assaying, with its origins in antiquity, is widely regarded as the best, if not the only, way to determine precious metals in naturally occurring ores. There are a lot of misconceptions about the universal applicability of fire assay methods and the more recent combination of traditional fire assay collection techniques with laboratory instrumentation has given rise to a serious, if not ludicrous, situation in the case of some materials.
There are some naturally occurring materials which cannot be successfully determined by fire assay. Some of those same materials can only be determined by instrumental techniques if their chemistry is understood.
Even the most sophisticated instruments in the world will not yield the correct answers if the chemistry of the ores being tested is not taken into consideration in designing the sample preparation and instrumental procedures to be used. Such considerations can only be made if the chemistry is understood, and such proper understanding requires the availability of a mind open to the fact that there may indeed by something new (to man) under the sun. It is important to appreciate the implications of the fact that naturally occurring materials may be in an unusual form; hence the need for a clear as well as an open mind.
The evaluation of precious metal deposits of a certain type involves an appreciation of their setting in terms of plate tectonics models.
Case histories of assaying problems with ores from south-western United States are presented which illustrate all of the above points. Attention is drawn to the possible implications of the phenomena described for mineral exploration in the UK as well as world-wide.