Schistose Rocks Research Articles

Contamination-effect in Ichifusayama granite(II)

Xenoliths included within Ichifusayama granite can be classified genetically into epixenolith (e. g., biotite schistose rock) and basic hypoxenolith (ec g., diabasic and or dioritic rocks) from various field and petrographical evidences. It is sufficiently clear that the granite has been contaminated with both of sedimentary and basic igneous rocks. The contamination behaviour in Ichifusayama granite is quite similar with those in Owase and Tanohata granites which are considered to have suffered contamination with some basic rocks. Accordingly, it is reasonable to consider that the granite, especially Ikenomoto type, has been more dominantly contaminated with basic rock rather than pelitic rock.

Rock-stratigraphic names for the South Island schists and undifferentiated sediments of the New Zealand geosyncline

Abstract In the South Island the rocks deposited in the New Zealand Geosyncline of Late Paleozoic and Mesozoic age now form three main belts, non-schistose sediments lying both to the east and discontinuously to the west of a schist belt. For the non-schistose sediments of the eastern belt the name “Torlesse Group,” derived from Haast's “Mount Torlesse Formation,” which was used in a similar sense, is proposed. For the median schist belt the name “Haast Schist Group,” named from the Haast River, is proposed, to embrace all the schistose rocks of the geosyncline.

Mineralogy and texture of the manganese ore bodies of Dongari Buzurg, Bhandara District, Bombay state, India, with a note on their genesis

The deposits include hard massive ores composed mainly of braunite, manganite, jacobsite, and vredenburgite associated with bodies of gonditic (quartz-spessartite) rock in the predominantly schist and quartzite terrain, and colloform manganese dioxide replacement ores in mica schists. The former type, like other gonditic ores of the Madhya Pradesh-Bombay manganese belt, resulted from metamorphism of manganiferous sediments. The replacement deposits have been attributed to supergene alteration and enrichment of the gonditic ores, but are here considered to reflect deposition from colloidal solutions which invaded the schistose rocks along foliation and fault planes.

Schistose rocks from St. Heliers Bay, Auckland

Summary Epidote amphibolites occurring as accidental blocks in the tuff of the St. Heliers Bay volcano and at Taylor's Hill, Auckland, are described. They are regarded as the product of the retrogressive metamorphism of a gabbroid intrusion into the basement rocks.

ROCK GLACIERS IN THE ALASKA RANGE

Field studies and examination of aerial photographs of approximately 200 rock glaciers in the Healy (1:250,000) quadrangle in the central Alaska Range showed that there are three types of rock glacier in plan: lobate, in which the length is less than the width (200–3500 feet long and 300–10,000 feet wide); tongue-shaped, in which the length is greater than the width (500–5000 feet long and 200–2500 feet wide); and spatulate, tongue-shaped but with an enlargement at the front. Lobate rock glaciers line cliffs and cirque walls and probably represent an initial stage; the other two move down valley axes and represent more mature stages. The rock glaciers are composed of coarse, blocky debris that is cemented by ice a few feet below the surface. The top quarter of the thickness is coarse rubble, below which is coarse rubble mixed with silt, sand, and fine gravel. Fronts of active (moving) rock glaciers are bare of vegetation, are generally at the angle of repose, and make a sharp angle with the upper surface. Fronts of inactive (stationary) rock glaciers are covered with lichens or other vegetation, have gentle slopes, and are rounded at the top. Active rock glaciers average 150 feet in thickness, inactive rock glaciers, 70 feet. The upper surface of most rock glaciers is clothed with turf or lichens. Sets of parallel rounded ridges and V-shaped furrows—longitudinal near the heads of some rock glaciers and transverse, bowed downstream, on the lower parts of others—and conical pits, crevasses, and lobes mark the upper surfaces of many rock glaciers. The upper surface of a rock glacier at the head of Clear Creek moved 2.4 feet per year between 1949 and 1957, and the front advanced 1.6 feet per year. Heights of the upper edges of the talus aprons along the fronts of rock glaciers average 45 per cent of the heights of the fronts. Each of these observations implies that motion is not confined to thin surface layers but is distributed throughout the interiors of the rock glaciers, which in this permafrost region are probably frozen. “Viscosity” has been calculated for rock glaciers at between 1014 and 1015 poises; for glacial ice it has been estimated at between 1012 and 1014 poises. Maximum average shear stresses within active rock glaciers range from 1 to 2 bars; these values are much larger than those calculated for solifluction and creep features. Rock glaciers occur on blocky fracturing rocks which form talus that has large interconnected voids in which ice can accumulate. They are rare on platy or schistose rocks whose talus moves rapidly by solifluction. The rock glaciers lie in an altitudinal zone about 2000 feet thick, centered on the lower limit of existing glaciers[1][1]. Although the firn lines on glaciers rise 1200 feet in a distance of 25 miles northward across the Alaska Range, the lower limit of active rock glaciers rises only 800 feet. The firn line on southward-facing glaciers is 2000 feet higher than that on northward-facing glaciers, yet in any given area southward-facing rock glaciers average only 200 feet higher than northward-facing rock glaciers. Insulation by the debris cover is believed responsible for the difference in altitudinal ranges between rock glaciers and glaciers. It is concluded that rock glaciers move as a result of the flow of interstitial ice and that they require for their formation steep cliffs, a near-glacial climate cold enough for the ground to be perennially frozen, and bedrock that is broken by frost action into coarse blocky debris with large interconnected voids. The longitudinal furrows are thought to result from the accumulation of ice-rich bands in the swales between talus cones at the head of the rock glaciers and the subsequent melting of this ice as the rock glacier moves down-valley. The transverse ridges are thought to result from shearing within the rock glacier that would occur where the thickness increases or the velocity decreases downstream. An average of 30 feet of bedrock was removed from source areas to form the present rock glaciers, indicating an average rate of erosion of 1–3 feet per year when they are active. [1]: #fn-1

X-Ray Study of Rare Phosphate Minerals

A RARE phosphate mineral assemblage is found in an abandoned mica pegmatite in Sorhee mica mine, north of Laldaiya Pahar (24° 47′ N., 86° 10′ E.; Survey of India, Sheet 72 L/1), Monghyr, Bihar. The main pegmatite, worked over a zone of about 200 ft. with a width of nearly 130 ft., intrudes schistose rocks striking N. 25° W. with a dip of about 60° towards W.S.W. The rare phosphate minerals occur as an aggregate, forming bands sometimes more than 2 in. wide and 8 in. long, veined with quartz. The X-ray powder diffraction study shows that the phosphate assemblage consists of graftonite (pale pink) and triphylite (bluish green) with traces of heterosite (purple). A brown mineral, the powder pattern of which is identical with that of rhodonite (manganese silicate), and an unidentified black mineral with rhodochrosite, pyrolusite, haematite and amorphous admixtures are also associated in the assemblage.

Some basic schistose rocks at the midstream of Horoman river in the southern Hidaka metamorphic province, Hokkaido

The writer presents some considerations on the genesis of some basic schistose rocks in the southern Hidaka metamorphic province.The basic schistose rocks described here are the schistose-plagioclase amphibolite (fine grained rock), the plagioclase amphibolite (medium grained rock) and the hornblende-plagioclase gneiss (coarse grained rock). It is concluded that most of the fine or medium grained basic schistose rocks are originated from the biotite rich hornfelsic rocks and the coarse grained basic schistose rocks are from the coarse biotite rich quartz-biotite-plagioclase rocks. The former two are products at the earlier stage of metamorphism and the latter is a product at the later stage of metamorphism in this district.

神居古潭結晶片岩中の特殊鉱物について

The Kamuikotan metamorphic complex develops as irregular long zone between the Mesozoic and Cenozoic formations along the western side of the Hidaka mountain ridge in Central Hokkaido. It runs about 200 km in a direction of nearly north to south, from areas of boundary of Teshio and Kitami Provinces to Hidaka Province.In general the normal Kamuikotan complex is made up the products due to slight regional metamorphism, in which the chief petrological members are black siliceous schists and next comes an abundance of green schists, small amonnts of quartzite, phyllite, mylonite and crysrtalline limestone are intercalated in the complex. From the geological and petrographical points of view, it may reasonably be assumed that the Kamuikotan complex can be readily correlated with the Franciscan formation in California.Comparatively large lenses or belts of the ultra-basic rocks run parallel with the trend of the Kamuikotan complex, being restricted mainly to the tectonic lines is the zone of the complex. It is noticeable that various interesting crystalline schists locally develop between the normal schistose rocks of the Kamuikotan complex and the ultra-basic intrusives, which have attracted special attention because of the presence of some special minerals, especially soda-bearing silicates. These special rocks may be a product brought about by contact metamorphic action due to ultra-basic intrusion and occurrence of the special minerals in them originated from pyrometasomatism, primarily owing to the action of some especially soda-rich hydrothermal solution drived from the ultra-basic intrusions.The subject matter of this paper is an outline of these some special minerals in the pyro-metasomatized rocks, with special reference to the general properties of the following members ; (A) glaucophane and crossite, (B) riebeckite and crocidolite, (C) aegirine-augite, (D) stilpnomelane, (E) piedmontite, (F) garnet, (G) lawsonite, and (H) pumpellyite.

Gneisses at the Saruru river district in the southern Hidaka metamorphic zone, Hokkaidô.

The gneisses of this district are classified, according to the structural views, into three main types as follows: 1. banded gneiss, 2. gneissose migmatite, and 3. schistose rock. The general trend of the rocks is NW-SE and the dip is 40°_??_60° NE. The banded gneiss occurs as a narrow belt along the marginal zone of the cordierite migmatite mass, while the gneissose migmatite and the schistose rock occur in the migmatite area. The banded gneiss and the gneissose migmatite are composed mainly of medium- to coarse-grained metamorphics such as biotite gneiss, garnet sillimanite-bearing cordierite muscovite biotite gneiss, kalifelspar biotite gneiss, tourmaline-bearing muscovite biotite gneiss, and sillimanite muscovite biotite gneiss, etc. The schistose rock is dark brown, and shows schistose or hornfelsic texture. It is composed of finegrained quartz, plagioclase, and biotite, containing muscovite, kalifelspar, and rarely garnet and tourmaline. In this paper, the results of volumetric relation of chief mineral constituents and plagioclase twin method are described and mutural relationships of the rocks are discussed.

A Consideration of Thermal-trandition in Metamorphic Process in the Southern Vicinity of the Tanzawa Mountainlands, Central Japan

Around the quartz-diorite mass of the Tanzawa Mountainland, Central Japan, there are developed various contact metamorphic rocks., Of these metamorphic rocks, those distributed in the southern vicinity of the quartz-diorite include various schistose rocks which range from chlorite-green schists to amphibolites., The problem of heat-trandition in the formation of these contact metamorphic rocks is discussed from a view point of heat-conduction and the results are compared with the actual metamorphic facies in these rocks., Lastly the relations between the model cases and the geological condition are discussed.,

Evaluation of Criteria for the Forcible Intrusion of Magma

Small Eocene rhyolite dikes in the Black Hills were forcibly intruded into steep-dipping pre-Cambrian schists and nearly flat Paleozoic rocks. Structural criteria for forcible intrusion are compelling in both rocks, but the full amount of deformation is measured only in the nearly flat strata. Larger dikes and stocks deformed the nearly flat Paleozoic strata, but deformational effects are difficult to detect in the steep-dipping schists, which suggests that criteria for forcible intrusion of magma into schistose rocks are poor, and negative evidence must be used with caution. Structural criteria for the forcible intrusion of a body as large as the Sierra Nevada batholith are still more unsatisfactory. However, there are indications that this batholith was built up by multiple intrusions of a number of small intrusive units, each showing about as much deformation of the schist wall rocks as do the smaller intrusive bodies of the Black Hills. An appraisal of evidence pertaining to forcible intrusion of magm...

Sapphirine from Dangin, Western Australia

While examining some vermiculite deposits at Dangin in 1940, on behalf of Messrs. Brisbane Wunderlich Co., Ltd., some rather friable gneissic to schistose rocks associated with one of the vermiculite occurrences were seen to contain an appreciable amount of a pale bluish mineral which from its optical properties was determined as sapphirine. As this was the first record of sapphirine from Western Australia, the mineral was separated and later chemically analysed at the Government Chemical Laboratory. Descriptions of the occurrence, characteristics, and genesis of this sapphirine and the associated rocks are set out in this paper.

Changing Patterns of Land Use in the Valencia Lake Basin of Venezuela

The lake, with an area of 440 square kilometers, occupies the center of a large depression of about 3000 square kilometers. With the Aragua and Tuy Rivers, it lies in a low valley, possibly downfaulted, which trends east-west for more than 200 kilometers between the Coast Range and the Serrania del Interior. The schists that form the high mountains north of the lake are probably the equivalent in age of the phyllites, schists, and slates of the Venezuelan Andes, which are definitely pre-Cretaceous. The mountain core has been intruded by acid rocks, chiefly granite, similar to the intrusives that outcrop in the Andean massif between Valera and Timotes and west of Chachopo.' The Serrania del Interior, south of the lake, is made up of intensely metamorphosed conglomerates, sandstones, limestones, and calcareous and carbonaceous shales. It is believed that all the north-central part of Venezuela was peneplained before the Coast Range was uplifted. After the peneplanation, which is of undetermined date, a general uplift took place, rejuvenating the streams. Since then relatively wide valleys and plains have developed, such as the plains of Aragua and Carabobo and, probably, the plain of Tinaquillo. The schistose rocks contain a great amount of ferruginous matter, which weathers to a deep red and stains much of the surface soil underlain by these rocks. In certain localities around the town of Valencia a thin layer of caliche covers the schists. The presence of limekilns in the region at first suggests an outcrop of limestone, but the indurated caliche is found to be full of small pieces of schist and flakes of mica. In some places along the north shore of the lake, notably at La

Geological reconnaissance across Sierra San Pedro Martir, Baja California

Sierra San Pedro Martir of northern Baja California is an elongated plateau—a slightly dissected fault block—which trends north-northwest along the axis of the peninsula. In a central east-west strip across the Sierra and its western foothills at about 31° north latitude the rocks include (1) an extensive metamorphic series of varied slaty and schistose rocks, striking northwest, and occurring chiefly in the foothills, (2) gneissic migmatites; occurring chiefly on the plateau.; and (3) stocks and batholiths of quartz diorite and granodiorite which are of uncertain, perhaps Upper Cretaceous age. The present report includes a reconnaissance geologic map of the previously almost unexplored area, and descriptions of the rock types found. Further work in this and neighboring areas is desirable, especially to clarify the structure and geomorphology, and to ascertain more definitely the ages of the various metamorphic and plutonio rocks.

West Highland Tectonics: Loch Leven to Glen Roy

I. Introduction The present paper is a sequel to my paper on the “Recumbent Folds in the Schists of the Scottish Highlands”, published in this journal in 1910, and expanded with certain corrections and discussions in a Geological Survey Memoir on the “Geology of Ben Nevis and Glen Coe”, 1916. The existence of these two publications allows of concentration on new features of interpretation. The Loch Leven referred to in the title is the salt-water loch of that name, between Argyll and Inverness-shire. The coastal parts of the district are well served by roads, railways, and steamers. There are also inland roads through Glen Etive, Glen Coe, Glen Spean, and Glen Roy. The main villages or small towns are Ballachulish, Kinlochleven, Onich, Fort William, and Spean Bridge. Accommodation is easy to get. The geological facilities include good exposures, high relief, and wonderfully definite lithology. Some of the mountains are carved out of Devonian igneous rocks, as at Ben Nevis and around Glen Coe, but much the greater number consist of the schistose rocks which concern us here. These peaks include a large number rising well above 3000 feet in height, and one, Aonach Beag, surpassing the 4000-foot level. When I described the Ballachulish stratigraphical succession in 1910, and again in 1916,1 was careful not to suggest an original order of superposition . I described recumbent folds, but left it to the future to decide which set of limbs was normal and which inverted. In 1922, however, I attempted a comprehensive treatment

Some South Australian Algal Limestones In Process of Formation

I. Introduction. This contribution serves to record three different types of limestone occurring in the south-eastern region of South Australia, now actually in process of formation, at least partly under the influence of plant-growth. Except for several small isolated inliers of ancient granitic and schistose rocks, and one localized outburst of Pleistocene basic volcanic activity, the south-eastern corner of South Australia between the Murray River, the Victorian border, and the sea is occupied by calcareous, almost horizontally-bedded rocks of later Tertiary age, overlaid irregularly by Pleistocene and recent formations. The whole area is flat, and but little elevated above the sea from which it has been reclaimed since the Middle Pliocene. The more southerly portion, and especially a wide coastal belt, has become dry land in Pleistocene and some of it even in Recent times. The low coast-line of sand-hills or soft honeycombed limestone extending from the Victorian border westwards to the mouth of the River Murray owes its trend and condition largely to the prevalence throughout the greater part of the year of strong southwesterly gales blowing inland from off the Southern Ocean. The activity of the wind has developed shore-line dunes, trending roughly in a north-west to south-east direction. Under this influence there exists inland from the coast for a distance of 30 to 50 miles, or even more, a parallel series of sandy dune-ridges separated by flat or depressed areas; the latter are from several to 10 or more miles in width. An excellent example of land

XI. The Pitchstone Porphyry of Penrioch, Arran

This Pitchstone, which is noted in the list of Arran pitchstones given in the Geological Survey Memoir (1903, p. 91) but which has not hitherto been described in detail, is exposed, for a few yards only, on the hillside about half a mile N.E. of Penrioch Farm, at the extreme south end of a prominent scarp marking the line of a fault. It is intruded into the ring of schistose rocks which surround the Northern Granite. The junction between the pitchstone and schist is not a sharp one the pitchstone having penetrated along joints in the schist and included blocks up to a foot in diameter. It is not clear from the field evidence whether the intrusion is a sill or a dyke, but it is probably the latter. In the hand specimen, the rock is a glossy, black pitchstone showing abundant large and conspicuous phenocrysts of felspar, smaller ones of quartz, and numerous xenoliths of a basaltic rock of aphanitic texture, hardly to be distinguished, macroscopically, from the schistose country rock. The fracture is splintery and uneven and the rock breaks up in diverse directions owing to the numerous cooling cracks which have developed. In thin section the rock is seen to consist of a base of pale yellowish brown glass, mottled a deeper brown in patches and crowded with minute microlites, which carries large phenocrysts of felspar and quartz and abundant microphenocrysts of pyroxene. The great majority of the microlites are of a ferromagnesian mineral, but occasionally felspar This 250-word extract was created in the absence of an abstract

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.

PROCEEDINGS OF THE EIGHTEENTH ANNUAL MEETING OF THE CORDILLERAN SECTION, HELD AT STANFORD UNIVERSITY, CALIFORNIA, APRIL 6 AND 7, 1917.

Session of August 6 The eighteenth annual meeting of the Cordilleran Section of the Geological Society of America was held at Stanford University, in conjunction with that of the Pacific Division of the American Association for the Advancement of Science, April 6 and 7, 1917. The first session, April 6, was called to order at 10 a. m. by Chairman C. F. Tolman, Jr. After announcement in regard to the annual dinner, to be held at Stanford Union at 6 p. m., and the business meeting for 1.45 p. m., the following papers were read: STRUCTURE OF THE LITHOSPHERE BY BAILEY WILLIS Presented extemporaneously. Discussion Dr. A. C. LAWSON expressed appreciation and asked for experimental data of a positive kind as to movement on plains of schistosity, calling.attention to the fact that schistose rocks sometimes break as easily across as with lines of schistosity. Dr. Willis explained, illustrating by use. . .

The Tourmaline-Corundum Rocks of Kinta (Federated Malay States)

I. I ntroduction : P revious L iterature . I propose in the following paper to describe and discuss the origin of certain rocks, remarkable alike in mineral composition and in structure, found in the Kinta Valley of Perak, the premier tin-field of the Federated Malay States. The two chief ingredients of these rocks are tourmaline and corundum; and it is evident, from the geological structure of the district, that they are the result of extreme metamorphism in beds associated with schistose rocks found chiefly on the west side of the valley, and perhaps also in thin beds intercalated with the crystalline limestone that generally forms the bed-rock of the tin-mines. The previous literature dealing with the Kinta Valley, or, indeed, with Perak as a whole, is very scanty, and does not take long to review. In 1882 M. J. Errington de la Croix described the geology of the Malay Peninsula (pp. 9–20), noticing the Kinta limestones as being widely developed. In 1884 the Rev. J. E. Tenison-Woods said that the granite ranges of Perak are flanked by ‘Lower Limestone ridges’ forming detached hills about 1500 feet high. ‘The limestone is crystalline, without a trace of organism[s], though lines of stratification can still be traced.... There is a Palæozoic sandstone, clayslate, or gneissose formation lying between the limestone and [the] granite. It is much decomposed, and gives rise to a red clay which generally goes by the name of laterite.’ In the same year the same author mentioned an instance of a recent volcanic rock