摘要:

The Claret Creek Ring Complex is one of several calc‐alkaline ring complexes in a Carboniferous epizonal batholith emplaced into continental crust at the junction of the Precambrian Georgetown Inlier and the adjacent Palaeozoic Tasman Geo‐syncline, northeast Queensland. Rhyolite ash‐flow sheetsplusrhyolite and dacite ring dykes are intruded by two comagmatic central stocks of microgranite and grano‐diorite‐tonalite. The complex may be chemically distinguished from the surrounding, contemporaneous batholith by its low K/Na, Rb/Sr and Th/K ratios. The origin and variation of its magmas is explained by invoking progressive partial melting of low K/Na basaltic andesites. Close relatives to the magma source‐rock are preserved as microdiorite xenoliths, which have contaminated their host granodiorite‐tonalite stock.

ISSN:0016-7614    

DOI:10.1080/00167617708728962

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

This short note presents the results of triclinicity determination of purified K‐feldspars from three spatially related granitic bodies (Kalunga Granodiorite, Watsonville granite, and Elizabeth Creek granite, ECG) in west Herberton, Queensland. The systematic decrease of triclinicity values (as 5 index) with increasing weight percent K2O and differentiation indices, decreasing colour indices, and K/Rb ratios is considered to provide an additional line of evidence for a possible co‐genetic relationship of the intrusives. The second phase of the Elizabeth Creek Granite (ECG II) is a late stage intrusive and its emplacement may explain the close spatial association of ECG members and the economic mineralization in the district.

ISSN:0016-7614    

DOI:10.1080/00167617708728963

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Detailed study of palaeosols in the sea cliffs between Long Reef and Palm Beach, north of Sydney, has given a much clearer idea of the environment and climate of the area during the late Scythian to early Anisian portion of Triassic time.

ISSN:0016-7614    

DOI:10.1080/00167617708728964

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Black Hill is a boulder‐strewn residual of norite standing 45 m above the Murray Plains about 80 km northeast of Adelaide. Between the boulders, the crystalline rock has weathered to a dark‐brown terra rossa‐rendzina soil with calcite, illite, kaolin, and hematite as the principal secondary minerals. At one site on the smooth lower slopes of the outcrop, the material above the norite consists of partially weathered granular fragments with considerable dolomite and some calcite in nodular form. Below the surface, the rock has been weathered along joints to produce the clay mineral nontronite, and between each corestone and this plastic clay there is a zone of laminated but essentially unaltered rock 10–25 cm thick. Pieces of amorphous silica occur sporadically in some joints and on the surface.

ISSN:0016-7614    

DOI:10.1080/00167617708728965

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Recently it has been argued that the structure of the island of Timor can be interpreted without invoking the concept of major overthrust‐faulting. Using evidence from the Maubisse area of eastern Timor, Grady (1975) has suggested that the relationship between contiguous rock units in that area may be interpreted either as an unconformity or as steeply dipping fault‐planes. In the present account interpretations of the structure of Timor are reviewed and the concept of overthrusting is reconsidered. It is concluded that the structure may only be interpreted in terms of a series of overlapping thrust slices resting on folded sediments of the Australian continental shelf. The lowest thrust sheet, the Kolbano thrust sheet is composed of internally deformed deep‐water calcilutites. It is followed to the north by the Lolotoi thrust sheet, made up of a complex group of crystalline rocks varying from granulite to slate, together with unmetamorphosed ophiolites, clastic sediments, and massive Miocene limestones. Overlying this group to the north is the Maubisse‐Aileu thrust sheet composed of Permian crinoidal limestones and volcanics in the south, passing northwards into shales and sandstones. Within this unit there is also a marked increase in deformation and metamorphism from south to north. Slates in the south pass into mica schists, psammites, marbles, and hornblende schists of the amphibolite facies on the north coast of eastern Timor near Manatutu. A further thrust‐slice composed of ophiolites rests on this thrust unit on the north coast of western Timor between Wini and Atapupu.

ISSN:0016-7614    

DOI:10.1080/00167617708728966

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Hydrogen‐ and oxygen‐isotope analyses of biotite (19), sericite (8), chlorite (2), quartz (27), and total rocks (37) from the Panguna porphyry‐copper deposit on Bougainville Island, place important constraints on the origin of the hydrothermal fluids responsible for mineralization and alteration in the mine region. Early high‐temperature amphibole‐magnetite alteration resulted from magmatic‐hydrothermal fluids. Several lines of evidence indicate 500°C as a realistic average temperature for mineralization, development of quartz veins, and biotitization processes. On the basis of mineral isotope data, responsible fluids could represent either18O‐shifted ground‐waters or magmatic‐hydrothermal fluids at submagmatic temperatures. Independent evidence, as well as total‐rock18O data, support the magmatic‐hydrothermal model.

ISSN:0016-7614    

DOI:10.1080/00167617708728967

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

A small andesitic intrusion, previously considered to be a Middle Cambrian lava, cuts fossiliferous upper Middle Cambrian sediments in the Leven Gorge section of the Dial Range Trough, northwestern Tasmania. Sixteen total‐rock samples of this intrusion produce a perfect‐fit, rubidium‐strontium isochron, which gives an Early Ordo‐vician age of 490 ± 18 m.y. for λ87Rb = 1.39 × 10‐11y‐1, and NBS 70A feldspar = 522 ppm Rb and 65.3 ppm Sr respectively. The initial87Sr/86Sr ratio of 0.7112 ± 0.0003 suggests a continental type intrusion rather than an island‐arc andesite. Rather similar intermediate igneous rocks, at least some of which are intrusive, are common in the Dial Range Trough and could be largely post‐Cambrian in age. From the geological time‐scale point of view, the only definite information obtained in this work is that the Middle‐Late Cambrian boundary is older than the date given above.

ISSN:0016-7614    

DOI:10.1080/00167617708728968

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Stratigraphic and structural observations indicate that the Encounter Bay Granites concordantly intruded the youngest formations of the Kanmantoo Group in the Mount Lofty Ranges metamorphic belt prior to the culmination of the first phase of folding and associated schistosity development recorded during the early Palaeozoic Delamerian Orogeny. Metamorphic textures in the metasediments of the Kanmantoo Group suggest that cordierite crystallized locally near the granites prior to and during theF1folding, whereas andalusite crystallized on a regional scale during theF1folding and in the post‐F1and pre‐F2static phase.

ISSN:0016-7614    

DOI:10.1080/00167617708728969

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Differential earth movements occurred during Eocene, Miocene, and late Caino‐zoic times. The faulting formed basins of sedimentation, led to dissection of land‐surfaces in some localities and burial in others, and faulted the Cainozoic sediments.

ISSN:0016-7614    

DOI:10.1080/00167617708728970

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

A critical evaluation of conflicting hypotheses for the deposition of the Hawkes‐bury Sandstone suggests that the Barrier Island‐Tidal Delta Model of Conolly (1969) is preferable to the Low Sinuosity River (Brahmaputra) Model of Conaghan & Jones (1975).

ISSN:0016-7614    

DOI:10.1080/00167617708728971

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor