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An examination has been made of the more important forms previously referred to the genus rhynchonella fischer de aldeas which occur in the chalk, with special attention to their internal structure. The morphology of the Mesozoic rhynchonellidae is discussed, and reference is made to the types of crura. Previous work on subdivision of Mesozoic form of Rhynohonella is reviewed. Reference is made to Wieniewska description of Rhynohonella; it is evident that no representatives of the genus sensu stricto have been recorded from the Chalk. The internal structure of Cyclothyris McCoy and that of Buckman's genus Stolmorhynchia to which he referred the Creteceous species invertebrates Rhynchonella sulcate (Parkinson), are discussed. Reference is also made to other Mesozoic Rhynchonellid genera including Lacunosella Wieniewska. Many Chalk Rhynchonellids were found to possess an internal structure similar to that of Stolmorhynchia Buckman and Lacunosella Wieniewska, and have been grouped in a new genus Platyrhynchia. They include the species Rhynchonella mantellianu (J. de C. Sowerby), P. wiestii (Quenstedt), R. cuvieri d'Orbigny, P. reedensis Etheridge and Terebratula obliqua James Sowerby, together with fourteen new species which are described in the paper. Rhynochonella plicatilis (James Sowerby) were found to have similar crura to those in Cyclothyris McCoy, but this median septum in the former is better developed. The species has been assigned to a new genus Cretirhynchia together with Rhynchonella Octoplicata (James Sowerby) Rhynchonella woodwardi Davidson, Rhynchonella limbata (Schlotheim) and four new species. Rhynchonella grasiana d'Orbigny, which is characterised by a well developed median septum and very fine costae is assigned to a new genus Capillirhynchia.

The Ben Loyal igneous complex forms a group of mountains, situated about six miles to the south of Tongue in northern Sutherland. The three plutonic masses of the complex are (a) The Ben Loyal range, (b) Cnoc nan Cuilean, and (c) Beinn Stumanadh. Though all three are composed essentially of syenites, each presents distinct petrographic features, and the Cnoc nan Cuilean mass, unlike the other two, shows a development of basic contact and basic marginal igneous rocks. The present paper is concerned primarily with the petrology of the Cnoc nan Cuilean mass, but the Ben Loyal intrusion is also considered in connexion with the form and structure of the complex. The country rocks are dominantly highly siliceous granulites of the Moine Series, which, beyond the area affected by the intrusions, dip at 20°- 30° to the south-east. As the igneous areas are approached, the strike tends to become parallel to the intrusion margins and the dips become steeper. It is suggested that the Ben Loyal and Cnoc nan Cuilean intrusions are irregular cones in shape, with their apices pointing downwards and with marginal sheet-like apophyses. The igneous rocks of the Cnoc nan Cuilean area are (a) the main syenite (pulaskite), composed, essentially of anorthoclase and albite (largely intergrown as perthite) and aegirineaugite (b) variable marginal syenites, consisting of more melanocratic syenites, "basic patches" (composed of aegirineaugite) and evident xenoliths. These are traversed by complex sets of pegmatite and aplite veins and small dykes. In the vicinity of the igneous mass the Moine granulites have been transformed metasomatically into rocks ranging from highly albitic granulites to aegirine-augite-schisis and hornblende-schists. Chemical and mineralogical evidence shows that the alkalies (principally soda) and alumina were "fixed" first and also possessed the greatest mobility. Later, such additional constituents as lime, magnesia and iron oxides formed, aegirine-augite and hornblende: these minerals attain their maximum development in the immediate vicinity of the contact. The source of the metasomatizing agencies is difficult to ascertain, but it seems very improbable that they were supplied by a syenitic magma. It is therefore suggested that "primary" alkalumina emanations displaced cafemic constituents from deep-seated "rocks of Lewisian type" thereby providing the materials necessary for the development of the marginal metasomatic rocks. The rocks of Lewisian type, which consist of hornblende-gneisses and schists, occur interbanded with the Moine granulites and, although they are not exposed at the surface nearer than the north-western slopes of Ben Loyal, there is structural evidence for their existence below the Cnoc nan Cuilean mass. The igneous contact itself is often characterized by transitions from basic schists to basic marginal syenites. A significant feature of these phenomena is the assumption of igneous characters by the more felspathic foliae of the schists and their injection into the basic bands. The contact transitions are considered to be rheomorphic phenomena, representing the final stage in the process of metasomatism, whilst the variable marginal syenites are interpreted as due to the hybridization of modified basic-metasomatic rocks (as represented by the "basic patches") by felspathic syenite magma("migma") of rheomorphic origin.

Of the ten Tertiary and pre-Tertiary alkaline igneous centres in Eastern Uganda, three (Budeda, Tororo and Toror) are described in this thesis, and a summary of a fourth (Napak) is presented. The earliest intrusive rock at Budeda and Napak is melteigite/pyroxenite which in both areas becomes converted to variable ijolite by replacement in the form of diffuse patches and well-defined veins. Melanite, wollastonite and calcite are characteristic of later phases of ijolite at Napak and Tororo. Nepheline syenites are produced by the development of feldspar in the marginal zone of the ijolites. At Budeda, cancrinite and calcite also occur in these rocks. They show intrusive relations with the fenites but are gradational towards the ijolite. At Napak, the cancrinite syenites and related feldspathic types occur as dyke-like masses within the ijolite. Feldspathization also affects the mixed rocks of the agglomerate (including ijolite and nepheline syenite) adjacent to the carbonatite at Tororo, locally producing orthoclasites. At Toror, the gneisses around the carbonatite are in places converted to feldspathic fenites (potash-feldspar rocks). Feldspathic breccias and intrusive rocks of similar composition (about 12% K2O) include trachytes, which evidently represent the mobilized products. The carbonatite at Budeda is a small mass formed by the replacement of melteigite, but at the other complexes it is clearly intrusive. Pyroxene, biotite and magnetite are considered to be derived from assimilated silicate rocks. Around the intrusive complexes fenites were formed by alkali metasomatism of the Basement. At Budeda syenitic fenites are widely developed, and have a foliated character which is related to early crushing. Locally the Budeda fenites are nepheline-bearing; they are also extensively feldspathized. The writer finds no direct evidence (with the exception of the trachytes) of mobilization of fenites to give rocks of the intrusive series. The intrusive rocks are considered to be derived from a melanephelinite magma, which by differentiation and the retention of volatiles led ultimately to the formation of a carbonatite residuum.

The results of detailed mapping confirm the Dalradian Succession suggested by E.B. Bailey, but his structural interpretation of the area proves to be incorrect. Mapping of the Baddoch Burn area indicates that the suggestion by Bailey of a complex system of slides contemporaneous with the original folding occurring in this region is also erroneous. It is shown from further field evidence that the region is affected by two major thrusts which, in this area of study, are developed on either side of the Blair Atholl Series. These thrusts divide the schists into three structural levels. The highest of these, the Morrone Nappe, is a primary structure in which the Ben Eagach Schist is overlain by the older Perthshire Quartzite. The thrust at the base of the Morrone Nappe is gently folded. The thrust-bounded Blair Atholl Series are squeezed out in the Clunie Lodge region, where the upper and lower thrusts merge, and bring the Morrone Nappe in contact with a lower nappe. In this locality the Ben Eagach Schist and the Perthshire Quartzite are exposed at a lower structural level. Three episodes of folding preceded the thrusting, and the main metamorphism was synchronous with, and overlapped the second folding. Garnet growth occurred during this F2 period, and was accompanied by kyanite and staurolite when these movements ceased. Contemporaneous with the third folding, many of the earlier formed minerals were replaced by chlorite. Biotite was also formed during this period and both minerals continued growing after this deformation. The thrust movements were followed by a sinistral folding about a near vertical axis, causing a marked change of strike in the vicinity of the Cairnwell. Finally normal faulting and brecciation of the country rock was associated with the intrusion of a suite of acid and intermediate dyke rocks.

The Husfjord area of Soroy essentially comprises a plutonic igneous complex which has been emplaced into Eocambrian meta sediments during the Caledonian orogeney. The metasedimentary envelope of the complex consists mainly of a sequence of psammites, pelites, semi-pelites, calc-silicate-schists, and metalimestones, which have suffered a prolonged regional metamorphism and two principal episodes of deformation. The regional metamorphic event commenced before the first folding episode, reached its peak in the almandine-amphibolite facies between the deformation episodes, and waned during the second period of folding. The various members of the igneous complex were emplaced synchronous with these metamorphic and tectonic events. Contact metamorphie effects produced by some members have been superimposed upon those of the regional metamorphism. The earliest member, the Husfjord metagabbro, was intruded towards the end of the first deformation episode, and has undergone the highest grades of regional metamorphism. A norite and a suite of diorites were emplaced during the second deformation episode and these have only suffered a low-grade regional metamorphism. The Husfjord metagabbro and the diorite complex were emplaced essentially by a mechanism of permissive intrusion. The latest members of the igneous complex were the Vatna gabbro, the Slatten gabbros, and a number of minor intrusions including perthosite sheets, basic dykes, and nepheline-syenite pegmatites. The main diorite suite appears to have developed from a dioritic melt, which was generated deep in the crust by the syntexis of sialic material with basic magma emplaced from beneath. Metamorphic mineral paragenesis in pelitic hornfelses suggests that the depth of emplacement of the Husfjord plutonic complex was in the order of 23 km.

The study area is situated on the northern extension of the Tuzgolu basin, (Central Anatolia) and contains Upper Cretaceous--Tertiary volcanic, clastic, and carbonate rocks with evaporites deposited on an ophiolitic melange basement, the Ankara Melange. The present structure of the area is the result of tectonism during late Alpine movements. The movements controlled the timing and conditions of sediment accumulation. The Bala basin evolved on the northern continental margin of the Kirsehir block. A brief period of south dipping subduction, which originated a continental island arc, was followed by oblique subduction, transform fault and continent to continent collision stages. These determined the shape and depositional characteristics of the basin. This is supported by independent magnetic evidence which suggests a 90° anti-clock wise rotation of the Kirsehir block during the Upper Cretaceous-Eocene period. Deposition of sediments occurred in two phases. The Upper Cretaceous-Middle Eocene phase contains seven formations, Four are believed to have been deposited in a deep marine environment by mass movements and turdidity currents sometimes forming submarine fans, and two are shallow marine to continental deposits. The seventh is composed mainly of Andean type calcalkaline volcanic rocks and their pyroclas-tics and was formed by subaerial lava flows. The formations reflect conditions of deposition in different parts of the basin and therefore some are the time equivalent of others. The Middle Eocene to probably Oligocene phase consists of two interfingering formations deposited in continental and marine environments of deposition. Palaeocurrent and petrographic data suggest that during the first phase, the source area was to the southeast and formed by volcanic rocks of Sarikaya formation and Ankara Melange, while in the second phase sediments were derived.

The Harsit-Koprubasi Cu-Pb-Zn sulphide deposit is located on the Black Sea coast about 3 km to the east of Tirebolu in the Giresun province of Turkey. It is one of the important polymetallic sulphide deposits occurring within the submarine volcanic environment of the Eastern Pontus ore province. Petrographic and chemical studies of the country rocks, despite their heavy alteration, show that they have similar features to the calcalkali rock series of orogenic belts. The investigated area exhibits submarine volcanic rocks and sediment intercalations. Volcanicity took place between Upper Jurassic - Lower Cretaceous and Oligocene - Miocene and is represented by three distinct cycles. The first cycle shows an almost total fractionation sequence, however the last two contain only basic rocks. The ore mineralisation of the area like most occurrences within the Eastern Pontus ore province, is associated with the so-called "ore-bearing dacite". The Harkkoy polymetallic and the Israil pyritic sulphide deposits have been studied for the purpose of comparison of their ore minerals with those of the Harsit-Koprubasi deposit. An electron probe microanalyser was used to determine the composition of the rock forming, and ore minerals, and also to compare various representatives of continuous isomorphous series of some sulphosalts. The majority of the analyses were of sphalerites; the Fe, Mn and Cd contents being found useful for purposes of comparison. Homogenisation and last-ice-melting temperatures of the fluid inclusions in sphalerite, quartz and barite crystals from the Harsit-Koprubasi deposit range between 239° to 338°C, and -1.0 to -3.1°C, respectively. From the evidence afforded by field, underground and borehole data, together with that from detailed chemical, mineralogical, fluid inclusion and electron probe studies on the ores, and country-rocks, the origin of the ore body and it's relation to the country-surrounding country rocks is discussed.

An investigation of the structures and metamorphic petrology of an area of Eocambrian rocks in Soroy, Northern Norway, forms the basis of this dissertation. The area is characterised by metasediments some of which enclose sheared lenticular bodies of metagabbro. Gneisses have been developed as products of granitisation. The stratigraphical order of the metasedimentary succession can be demonstrated by reference to sedimentary structures preserved in massive psammites. From this evidence, it is manifest that strata are Inverted over a large part of N.E. Sry, this inversion being attributed to the presence of early recumbent folds of considerable magnitude. In the surveyed area, major folds of a later, second deformation episode dominate the structural picture and refold the early structures. The second episode of folding was protracted and consists of two distinct phases. The main folding occurred early in this period while the later phase is characterised by a brittle deformation. Generally, second episode folds display monoclinic symmetry though in the south and west there is no uni-directional sense of fold overturning and the symmetry of movement is apparently orthorhombic. This difference of fold symmetry is clearly related to an orthogonal swing of strike direction. Textural studies of the metasediments in relation to the tectonic episodes allow a subdivision of the metamorphic history into a number of phases. A low grade metamorphism accompanied the early folding. The highest grade of regional metamorphism was established late in the static Interval separating the first and second deformation episodes. Coeval with this, a granitisation of the metasediments was effected which continued, in part, into the second episode of folding. Diaphthoretic phenomena characterise the later phase of brittle deformation.

The thesis presents results of a study of over 900 square miles of country round the southern end of Lake Malawi, the geology of which was previously unknown. The complex structure of the Basement series of crystalline rocks which are exposed on either flank of the Rift results from two episodes of deformation producing superimposed sets of folds with NNW-SSE and NE-SW trending axial planes. These rocks, which are probably largely of sedimentary origin, show a common imprint of granulite facies metamorphism, but the widespread occurrence of disequilibrium textures and biotite in them shows them to have suffered retrogressive changes. The retrograde changes are associated with a growth of microperthitic felspar, extreme development of which gives rise to palingenetic perthositic syenites and quartz-syenites. These syenites are broadly syntectonic with the second deformation; an alkali metasomatism leading to syenitisation, reactivation and partial mobilisation of a pre-existing crystalline Basement is thus indicated. The repeatedly folded polymetamorphic Basement rocks have been intruded, apparently under epeirogenic conditions, by later series of microcline-granites and alkali-syenites. Recent work on radiometric dating has shown that episodes of intrusion of microcline-granites occurred in the region of the Malawi Rift in the Lower Silurian and the Middle Permian, and of alkali-syenites in the Lower Cretaceous, and correlation of the Fort Johnston intrusions with these events is suggested. An account of the minor intrusions of the area is also included. The marked structural asymmetry of this part of the Rift is demonstrated, and the Rift faulting and its relation with the pre-existing structures is examined and discussed. A description of the physiography of the area is given which includes the south-eastern extremity of the Lake, its basin, its shorelines, and its only outlet, which lies within the area mapped.