Series Of Schists Research Articles

Ordovician passive continental margin magmatism in the Central-European Variscides: U–Pb zircon data from the SE part of the Karkonosze-Izera Massif, Sudetes, SW Poland

Approximately 500-Ma-old orthogneisses are widespread in the eastern part of the Variscan belt and are commonly interpreted to have intruded mica-schist series of assumed Neoproterozoic age. New SHRIMP zircon ages of quartzofeldspathic metavolcanogenic rocks of the mica schist series in the eastern part of the Karkonosze-Izera Massif (SW Poland) indicate that they are late Cambrian/early Ordovician rather than Neoproterozoic in age, based on the zircon age spectra distributed mainly between ca. 500 and 660 Ma (with a few Proterozoic inherited minimum ages of ca. 970 and 1,825 Ma). Younger zircon dates, dispersed between ca. 412 and 464 Ma, are interpreted as a result of Pb-loss likely caused by subsequent metamorphism. Consequently, the felsic metavolcanogenic rocks appear to be roughly contemporaneous with the intrusion of ca. 500-Ma-old orthogneiss protoliths (with the pooled concordia age of 487 ± 8 Ma interpreted as the best approximation of the protolith intrusive age). Field relationships, petrological and geochemical features of the felsic and mafic rocks studied support a model in which the accompanying mica schist series are not the original country rocks to the ca. 500 Ma granite intrusions, and indicate that their recent close proximity is the result of tectonic juxtaposition. However, both the mica schists enclosing the bimodal metavolcanic rocks, and the orthogneisses, are interpreted to represent a Cambro-Ordovician passive continental margin sequence being part of the Saxothuringian domain. They are tectonically overlain to the east by HP/T metamorphic units, comprising MORB-type metaigneous rocks, and delineating a tectonic suture separating the Saxothuringian block in the west from an assumed continental block (Tepla-Barrandian) to the south-east.

NEW EVIDENCES OF THE LOW-P/HIGH-T PRE-ALPINE METAMORPHISM AND MEDIUM-P ALPINE OVERPRINT OF THE PELAGONIAN ZONE DOCUMENTED IN METAPELITES AND ORTHOGNEISSES FROM THE VORAS MASSIF, MACEDONIA, NORTHERN GREECE

Pelitic rocks of the pre-Alpine "gneiss series" from the Voras Massif record a polymetamorphic history of three metamorphic events; a first HT event indicated by migmatitization phenomena, a subsequent LP-HT event (andalusite-sillimanite series) at 2.5-3 Kbar and 610-640°C, and a third medium-P event at ~11 Kbar and ~550°C. The LP-HT metamorphism is associated with intrusion of Variscan granitoid plutois in a magmatic arc setting. The medium-P metamorphism records an Alpine event (probably Early Cretaceous) indicated by kyanite, chlohtoid, garnet and staurolite formation replacing andalusite and cordierite. The Variscan granitoids and the overlying lithologies of the "schist series" are affected only by the medium-P metamorphism. Granitoids are transformed into phengite orthogneisses having the mineral assemblage phen (Si=3.35-3.47 a.p.f.u.)±Bt-Ab-Kfs- Qtz±Czo±Grt and high-alumina pelites into gamet-chloritoid schists with the mineral assemblage Grt-Ctd-Chl-Ms-Qtz-Rt±llm. The "schist series" which underlies the Late Triassic-Early Jurassic marbles and overlies lithologies of the "gneiss series" and metagranitoids represents protoliths of the Permo-Triassic volcanosedimentary series deposited at the eastern margin of the Pelagonian continental block

Geological and Petrographic Base Studies for the Mountain Hazards Mapping Project in the Kathmandu-Kakani Area, Nepal

The geology and petrography of the area between Kakani and Kathmandu, Nepal, was studied to provide a basis for mapping mountain hazards. The study showed a close relationship between rock type and structure, degree of weathering, and susceptibility to landsliding and gully erosion. In addition the soil mineralogy indicates rather immature soils. Five rock units were recognized: a two-mica gneiss series primarily affected by an upper amphibolite facies metamorphism and later over-printed by greenschist facies metamorphism; marble-, quartzite and phyllite-, biotite gneiss-, and schist series that were only affected by the later metamorphism; tourmaline-muscovite granites and associated pegmatites that have been intruded into the other rock units.

Particularites chimiques et mineralogiques de la serie meta-evaporitique du gisement de pyrite de Niccioleta, Toscane, Italie

Abstract The chemical composition of the meta-evaporitic series of Niccioleta is similar (evaporitic rocks excepted) to that of the common mica schist series. However, the sheet silicates have recorded the evaporitic nature of the sedimentation. Only the schist layers in the anhydrite rocks have relatively high Mg and B contents. Electron microprobe analysis proved that muscovites are more phengitic and more magnesian in the evaporitic rocks than in the schists. Small amounts of Mg-bearing chlorites and phlogopites are associated with the phengites (which contain micro-inclusions of tourmaline, rich in dravite). The sedimentary origin of the magnesian character is discussed, the magnesian aggradations of illites are the main factor; typical minerals of evaporite-bearing sediments, like smectites and corrensites do not appear in large quantities. The P-T conditions of regional metamorphism are postulated as 2-3 kbar and 400-450 degrees C.

Unmetamorphosed Volcanic and Sedimentary Xenoliths in the Kimberlites of Sierra Leone

THE dominant xenolith types in the kimberlites of the Sefadu area of eastern Sierra Leone are granite, amphibolite and amphibole-schist derived from the wall rocks. Eclogite and dunite xenoliths are only rarely encountered. Small inclusions of a suite of virtually unaltered volcanic rocks and derived sediments for which no counterpart is found in the mapped country rocks of the area are a feature of the kimberlite now exposed by mining at Koidu. I recently collected a series which included undeformed amygdaloidal basalt, clastic basaltic sandstone, fine-grained basic tuff, fragmental andesitic tuff and calcareous tuff. The kimberlites occur in granite emplaced in the Pre-Cambrian Kambui Schists, a strongly metamorphosed schist series of largely volcano-sedimentary parentage1,2. The unaltered xenolithic material in the kimberlites is most readily explained as being derived from an overlying sequence of volcanic and associated sedimentary rocks, now removed by erosion.

Schwefelisotopen-untersuchungen an sulfiden aus den erzvorkommen der sierra de cartagena in Spanien

Sulphur isotope ratios are reported for 166 sulphide samples (galenite 72, shalerite 44, pyrite-marcasite 44, pyrrhotite 4, chalcopyrite 2) and for 2 barytes from the ore deposits in the Sierra de Cartagena, Spain. The range of S-isotope ratios is relatively narrow within each mine, within the 3 subdivided zones and within the whole mineralised region, which contains different types of ore deposits: I. Layered deposits: in the Palaeozoic schist series (1; 2a), in the contact between these metamorphic schists and the overlatned Triasic dolomite (2b) or in Tertiary conglomerate horizons (2c); II. Crosscutting veins: in the Palaeozoic schist series (3a), (mainly in marble horizons) and in Tertiary igneous rocks (different types of andesite) (3b). The Cartagena sulphides display an arithmetical isotope average of δ 34 S = +3.6%., Only a few samples of pyrite-marcasite show significant deviations with sulphur isotope values of about δ 34 S = +37.0 or −42.0 per cent. These Fe-sulphides belong to a younger FeS 2-generation. The S-isotope ratios of different sulphides differ only slightly from each other, the rule is: δFeS > δFeS 2 > δZnS > δPbS. The very small range of S-isotopes is typical for only one process of mineralisation. In the present case a subvolcanic-hydrothermal mineralization in connexion with the upper Tertiary subvolcanic activity is proposed.

La virgation sud-rifaine; recherches sur la marge sud du sillon rifain (secteur Haut-Ouergha-Haut-Leben)

Abstract Describes the structural units of the region between Haut-Ouergha and Haut-Leben, Morocco, which occurs in the central part of the Rif virgation, a zone of successive differential overthrusts. The tectonic relations of overthrust Jurassic limestone masses and the Mesozoic schist series of the Rif trough (mainly Cretaceous) are discussed in particular.

"Coutchiching" of Thunder Lake, Ontario

A mica schist series near Thunder Lake, District of Kenora, in northwestern Ontario, has been heretofore regarded as pre-Keewatin or Coutchiching. A field study of this series by the writer radically revises older mapping and proves the sediments to be younger than a Keewatin hornblende schist complex. The sediments, however, contain a minor greenstone flow series. A less metamorphosed greenstone series is also present, but faulting makes age relations of this series uncertain. Basic intrusives are associated with greenstones and sediments. Batholithic granites and pegmatites cut all other rocks of this area.

Geology and Mineral Resources of Central and Northern China.

The Three of China's “Five Holy Mountains”, the Tai-shan in Shantung, the Sung-shan in Honan, and the Hua-shan in Shensi are formed of the Archaean rocks or the Tai-shan complex, so called after the first named. The complex is composed chiefly of crystalline schists and gneisses, with intrusions of granites and of various dykes of a later age, probably pre-Cambrian. Another series of schists and gneisses, assigned to the early Proterozoic, occurs in a typical development in the Wu-tai-shan district of northern Shansi, after which it is named the Wu-tai system. Although an actual contact of the Tai-shan complex with the Wu-tai has not yet been ascertained, an unconformable relation can easily be inferred from their lithological and structural features.Widely distributed throughout China limestones occur in several thick beds, each attaining a thickness of some 1, 000 meters or more, in which many beautiful canyons are carved out. In Northern China are found two thick beds of limestone, the Nan-kou limestone (Sinian) and the Ki-chou limestone (Cambro-Ordovician), while in the Yangtze valley at least four beds may be enumerated, namely, the Tong-ying (Sinian), I-chang (Cambro-Ordovician), the Yang-hsin (upper Car-boniferous to Permian), and the Ta-yeh (Permian to Triassic). The Sinian lime-stones are underlain by a sequence of arenaceous and argillaceous beds, in which sedimentary hematite deposits of the Lungyen type are interbedded. In Central China upon the I-chang limestone lies a thick succession of limestone, shale, and sandstone, which falls within Silurian, Devonian, and lower Carboniferous, while in Northern China the Ki-chou limestone immediately underlies a coal-bearing formation of Permo-Carboniferous age, showing a hiatus of the first magnitude. Red formations, ranging from Triassic to Cretaceous in age, are characteristic features of basin areas, of which the Szechuan and the Shenpei basins are most important. The most remarkable superficial deposits are Pleistocene loess in Northern China and Pliocene red-earth with vermiculated mottling in Central China.There are four principal periods of igneous activities since Mesozoic time. The first period, very likely included in late Jurassic, is represented chiefly by granitic and andesitic rocks, the second, probably in early Cretaceous, by liparitic and andesitic eruptions, the third, in middle Cretaceous, by granodiorites, syenites, granites and porphyries, and the fourth, in early Tertiary, by basaltic flows.According to both productions and reserves hitherto estimated the following seven may be mentioned as principal mineral resources in China: coal, tungsten, antimony, tin, iron, gold and aluminous shales, of which the first three are of the world importance.The probable coal resources estimated by the Chinese Geological Survey in 1934 are 239, 100 million tons; of which according to geological age 60 per cent are Palaeozoic, 36 per cent Mesozoic, 4 per cent of unknown age; classified according to kinds 77 per cent bituminous coal, 19 per cent anthracite, 1 per cent lignite, 3 per cent unclassified; according to regions 89 per cent Northern China, 6 per cent Central, 1 per cent Southern, 4 per cent Northwestern. Our estimate is about 300, 000 million tons with Shansi alone, exceeding the above total by some 600 million tons.Iron are deposits may be classified into seven types, namely, sedimentary, hydrothermal, contact, magmatic, regional metamorphic, residual and detrital, the first three being most important. The total reserve of iron are has been estimated at about 323 million tons, of which 172 in Mimi tons are in Northern China, 117 million tons in the Central and remainig 34 million tons in the Southern. According to our estimation the total figures of reserves, each above 1 million tons, are about 368 million tons.

On the so-called "Mikabu System" in the Vicinity of Hukuoka, Kyusyu.,

In the neighbourhood of the city of Hukuoka, northern Kyusyu, there are alternations of green (metamorphic) rocks and crystalline schists., In contrasts to the occurrence of the similar rocks in the outer zone of the Japanese Archipelago, where, developed in distinct facies, the green rock series (the Mikabu Series) are commonly considered to be geologically younger than the crystalline schist series (the Sambagawa Series), both kinds of rocks here, occurring intimately associated, may reasonably be supposed to be of the same age (probably Palaeozoic) differing only in degree of metamorphism.,

The Problem of the Martic Overthrust and the Age of the Glenarm Series in Southeastern Pennsylvania

The Glenarm series of schists, marbles, and quartzites of the Atlantic Piedmont has been assigned to the pre-Cambrian in numerous recent papers. The apparent superposition of these rocks on strata of known Paleozoic age near the northwestern margin of the Piedmont province is explained by the Martic low-angle overthrust fault. It is the purpose of this paper to reopen the Glenarm-Martic problem by presenting evidence that suggests, first, that the Glenarm Series in southeastern Pennsylvania may be wholly or in part Paleozoic, and, second, that the Martic overthrust does not exist.

The Metamorphic Rocks of Gunong Terendum, Kinta Valley, Federated Malay States

IN a previous paper in this Magazine, as well as in an official report to the Government of the Federated Malay States and in a paper in the Mining Magazine, I have discussed in some detail the geological relations of the pregranitic sedimentary rocks of the Kinta Valley, in the State of Perak, F.M.S.1 The relations of the mainly calcareous Raub Series of Permo-Carboniferous age and the rocks generally known locally and colloquially as the “ Schist Series ” (Triassic and perhaps Rhaetic), formed one of the principal subjects on which I was requested to report to the Government. My conclusions were, I think, sufficiently clearly expressed in the publications quoted, and it is unnecessary to repeat here the arguments and field evidence which led me to those conclusions.

The Pre-Cambrian Greenstone Complex of the Jerome Quadrangle

In the Jerome quadrangle are a series of greenstones varying in composition from andesites to rhyolites, principally the former, which are pre-Cambrian in age. Heretofore these greenstones have been included with the Yavapai schist series, but detailed mapping shows them to rest unconformably on the upturned and eroded edges of the schist. The greenstones are therefore younger than the typical Yavapai schists and are believed to be older than the Grand Canyon series. The structural features of this complex and the contact action of the pre-Cambrian granitic masses are also described in this article.

The Limestone of the Kinta Valley, Federated Malay States

Summary and ConclusionThe following is a very brief summary of the results of my investigation of the problems here dealt with:—(1) The limestone is Carboniferous or Permo-Carboniferous or more probably both.(2) All the limestone belongs to one continuous phase of deposition.(3) The “Schist Series” is above the limestone, and is of Triassic age.(4) The western boundary of the limestone is a great fault or system of faults.(5) The thickness of the limestone is indeterminable, but is probably to be measured by thousands of feet.(6) The limestone hills are due to overfolding from the west, modified by block-faulting and denudation.

The Northern Range of Trinidad

The northern mountain range of schistose rocks of the Island of Trinidad reaches an altitude of 3,012 feet in Mount Tucutche and consists of a wild and tumbled mass of ridges with deep intervening valleys clothed from top to bottom with tropical vegetation, the abode of a practically undisturbed fauna and flora. Westwards the range is continued in the rugged and precipitous islands of Monos, Huevos, and Chacacare between which are the Bocas through which ships pass in entering the Gulf of Paria from the north. The entrance to the Gulf is famous for its scenic beauty. North-eastwards the schist-range reappears in the island of Tobago, but no limestones are reported to occur among the rocks there. Westwards the high range of schistose mountains continues along the northern coast of a great part of Venezuela,4 and over 800 miles further west at Santa Marta in the Kepublic of Colombia I have seen a series of schists very similar in lithology to those that form the northern range of Trinidad.

Radiolarian Jaspers in the Brisbane Schist Series.

Radiolarian Jaspers in the Brisbane Schist Series.

The Geology of Mining Areas

MR. R. G. MCCONNELL has contributed to the “Annual Report of the Geological Survey of Canada,” vol. xiv., part B (1905, price 25 cents), a well-illustrated paper of wide interest on the Klondike gold-fields. The general topography and the communications with other regions are described, and the full-page landscapes convey an excellent idea of the conditions under which mining is carried on. Roads have been developed, the White Pass railroad is completed, and it now takes less than a week to reach Dawson City from Vancouver. In the latitude of only 60° N., the surface-stratum is continuously frozen, and unfrozen ground is reached at depths of from 60 feet to 200 feet. In summer, gravel-beds which are unprotected by moss thaw down to a depth of from 6 feet to 10 feet (p. 9). The gold-bearing quartz-veins are included for the most part in the Klondike series of schists. Microscopic evidence supports the view that these schists are of igneous origin, since a passage is traceable from uncrushed granitoid types to mylonitic sericite-schist (p. 19). Cainozoic rocks are found folded in with the schists in Last Chance Creek, thus proving the recency of earth-movement in this area. In the basin above Rock Creek these beds contain lignites of Upper Eocene age. The low-level gravels of the creeks, which are so important to the gold-miner, include bones of the mammoth, as well as of many existing northern animals (p. 29). The greater part, at least, of the Klondike gold is detrital, and is derived from the small but very numerous quartz-veins associated with the older schists (p. 61). Many of the grains of alluvial gold enclose quartz, and a few are themselves enclosed in quartz. The decay of the rocks must have been enormous to allo* of the vast accumulation of auriferous gravels. The quartz-veins are much younger than the schists in which they lie, but are older than the andesites and quartz-porphyries of the district. Lodemining has so far made little progress, but work among the gravels seems still, increasing.

The Geological Structure of Scandinavia and the Scottish Highlands

THE obvious connection and analogy between the geological structure of the crystalline rocks of the Highlands of Scotland and those of Scandinavia have long engaged the attention of geologists. Among the northern observers to whose labours we are largely indebted for our knowledge of the Scandinavian regions, Dr. A. E. Törnebohm has proved himself a keen and indefatigable explorer of the Swedish uplands. Many years ago he showed that above clay-slates and limestones, with recognizable Silurian fossils, there lies a great thickness of quartzites, gneisses, and schists, called by him the Seve group. In more recently studying the relations of these rock-masses, he encountered some great difficulties, of which he sent me at the time an account. I could not pretend to solve them, but suggested, as at least a working hypothesis, that the Scandinavian structure might be fundamentally similar to that now recognized as characteristic of the North-West Highlands, where the apparent conformable superposition of a series of schists upon fossiliferous Lower Silurian strata has been produced by great terrestrial displacements, whereby the overlying rocks have been crushed and deformed, until they have assumed a new crystalline structure along the planes of movement, these stupendous changes having occurred at some time subsequent to the Lower Silurian period. I have recently received from Dr. Törnebohm the following letter, which he gives me leave to publish, and which will no doubt be read with interest by those who are aware of the recent progress of research in this subject:—“It will perhaps interest you to learn that your suggestion four years ago regarding the construction of our Scandinavian filds has turned out to be correct, at least in my opinion. My late researches have little by little driven me to the conclusion that the crystalline schists belonging to what I have called the ‘eve group’ have been placed over Silurian strata by an enormous eastward thrust. I admit that I have most reluctantly come to this conclusion, knowing that it implied a horizontal thrust of enormous masses of rock for more than 100 kilometres. Such a stupendous movement of entire mountain-regions is hard to realize; but facts are stubborn things.”

Metamorphic Rocks of Bergen 2

THE metamorphic rocks of the Bergen Peninsula in Norway continue to attract the attention of Norwegian geologists, and we have before us, as an addition to the well-known works of Naumann, Leopold von Bucb, Esmark, Keilhau, Kjerulf, and Hjörtdal, a new elaborate and interesting work by M. Hans H. Reusch, which deals with the same subject. These rocks consist, as is known, of a variety of quartziferous talc-mica schists, diorite, clay-slates, conglomerates, and strongly-developed gneisses and granites. Various and very different opinions have been expressed as to the origin of these rocks. The researches of M. Reusch give a key to this question, as he has discovered in the clay-slates, which seem to constitute the upper part of these vertical strata, numerous fossils belonging to the lower part of the Upper Silurian formations, namely Halysites catenularia and Cyathophyllum, changed into white calcareous spar, a few tubular bodies (presumably Syringophyllum organum), some gasteropods (Murchisonia or Subulites?) some trilobites, as Calymene, also Phacops or Dalmannites, and some brachiopods. The presence ot these fossils is the more interesting as the whole series of schists was often considered as of igneous origin. As to the gneisses and gneisso-granites of the peninsula, M. Reusch has given great attention to their structure and to the remarkable results of pressure which the rocks have under gone. He shows how granitic veins were folded and crumpled, how a kind of transversal stratification has arisen in beds of stratified gneiss under the influence of pressure, and he con cludes, from an accurate study of the subject, that altogether the rocks show a far greater degree of plasticity than might have been supposed. “It seems that there are masse, as, for in stance, the gneiss of Svenningdal, that have on one side a true stratified structure (not merely parallel or schistose structure) which could hardly be found in a rock of igneous origin, and on the other side send veins, or have included fragments which have undergone metamorphic changes.”