摘要:

The McBride Volcanic Province of northern Queensland covers an area of about 5000 km2, and is composed of basaltic lava flows erupted from many large and small volcanoes. An older series of basalts, preserved in mesas, have K‐Ar ages in the range 7.3 to 7.8 m.y., late Miocene. Most of the volcanic rocks of the Province were erupted in the interval from 2.7 m.y. ago (late Pliocene) to almost the present day. No significant break in the volcanism is recognized during this younger period of activity. The K‐Ar ages are consistent with the stratigraphical control, based mainly on geomorphological evidence.

ISSN:0016-7614    

DOI:10.1080/00167617508728905

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Podiform chromitites from ultramafic belts in New South Wales are interpreted as modified cumulates of three principal textural types.

ISSN:0016-7614    

DOI:10.1080/00167617508728906

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Crystallization of stilpnomelane and pumpellyite, disappearance of prehnite and development of assemblages containing the pair pumpellyite‐actinolite, and disappearance of pumpellyite, define isograds separating four zones of progressive regional metamorphism in the Nambucca Slate Belt of northeastern New South Wales. Mineralogical changes are paralleled by textural changes in metaclastic rocks. Detrital grains are progressively modified, a preferred orientation of material becomes increasingly perfected, and a foliation develops as grade increases.

ISSN:0016-7614    

DOI:10.1080/00167617508728907

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The Mount Black lead‐zinc deposit at Cooleman Plains, southern New South Wales, occurs in the uppermost part of the moderately folded, weakly metamorphosed, Upper Silurian Cooleman Limestone. A joint‐controlled collapse‐breccia zone interpreted as a palaeokarst structure has been partly replaced by quartz, sphalerite, galena, and a little chalcopyrite, pyrite, marcasite, tetrahedrite, arseno‐pyrite, and mackinawite. These minerals show evidence of having encrusted and replaced limestone fragments in the breccia. Oxidic Zn, Pb, Cu, and Fe minerals have formed by the near‐surface oxidation of the sulphides.

ISSN:0016-7614    

DOI:10.1080/00167617508728908

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

A recent benthonic foraminiferal population consisting of 144 species from an interacting marine‐estuarine environment has been analysed by Q‐mode cluster analysis to reveal biotopes. Simplification of the total populations, both in terms of abundance and occurrence, discloses that the more significant subpopulation is composed of the widely‐occurring species. Subpopulations based on rarely occurring but locally abundant species do not define meaningful biotopes.

ISSN:0016-7614    

DOI:10.1080/00167617508728909

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Three Australian Ordovician graptolite faunas are described; the short‐lived Anisograptid Fauna is followed by the Dichograptid Fauna, which in turn is succeeded by the Diplograptid Fauna. The Dichograptid Fauna consists of two sub‐faunas, the Tetragraptus‐Didymograptus and the Isograptid; the Diplograptid Fauna consists of the Glyptograptus‐Amplexograptus and the Leptograptus‐Orthograptus sub‐faunas. The Diplograptid Fauna becomes extinct low in the Silurian, giving way to the Monograptid Fauna, which persists into the Devonian.

ISSN:0016-7614    

DOI:10.1080/00167617508728910

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

In the Precambrian rocks west and southwest of the Mount Isa Fault three significant fold generations are recognized. Within individual successions, units containing an early phase of deformation are juxtaposed by a late fault against a sequence that does not share these earlier events.

ISSN:0016-7614    

DOI:10.1080/00167617508728911

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Flared slopes originate as concave weathering fronts beneath the regolith, and several other minor granite landforms found in association with them (tafoni,Rillen)may be initiated subsurface also. Other features, particularly incipient gnammas and gutters, have been observed on surfaces that have only recently been cleared of granite debrisin situ.

ISSN:0016-7614    

DOI:10.1080/00167617508728912

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Examination of quartz from plutonic source rocks, sediments and soils, using both optical and scanning electron microscopes, reveals that the mineral is, almost always, cut by sets of partially healed, subplanar, subparallel microfractures dividing it into sheets typically one to a few micrometres thick. The structure, which originates in source rocks, is not due to crystal cleavage although it does show weak crystallo‐graphic influence in its directions. One to several sets of microfractures, intersecting at varying angles, can be present in any one quartz crystal. The microfractures vary in quality like cleavages; separation takes place readily along some, less so along others.

ISSN:0016-7614    

DOI:10.1080/00167617508728913

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Thirty biotite and two muscovite ages are reported from thirteen plutons in the Berridale Batholith, a thoroughly mapped composite batholith in southeastern Australia. Middle Ordovician country rocks place an older limit on the age of the batholith.

ISSN:0016-7614    

DOI:10.1080/00167617508728914

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor