The Bendigo goldfield, which has produced most of Victoria’s gold 22 million ouncess684.3 ton., consists of numerous deposits located mainly along narrow, parallel-trending anticlinal domes separated by 100 to 400 m. The individual domes are parts of a regional anticlinorium in Lower Ordovician sedimentary rocks. Highest gold ore values are generally located in the eastern limbs and particularly in the apical areas of the smaller individual anticlinal domes and in the central part of the more regional-anticlinorium.

Alteration present in metasandstone units in the Nell Gwynne anticline consists of phengitic sericite to 15 vol%., chlorite to 7%., carbonates siderite, sideroplesite, ankerite and calcite, to 10%. and sulphides arsenopyrite, pyrite, chalcopyrite and sphalerite, to 5%.. The alteration generally follows the trend of the structure extending upward and above mineralisation in anticlinal areas and below largely unmineralised synclinal areas. Phengitic sericite extends furthest, to at least 150 m above mineralised saddle reef positions, chlorite to 130 m, sulphides to 80 m and carbonate to 50 m. Chlorite geothermometry suggests temperatures of 260 to 2908C for the alteration. The sequence of carbonate precipitation generally is from siderite early., sideroplesite, ankerite and calcite. The more Fe-rich carbonates tend to occur near the apical parts of the anticlinal domes. Arsenopyrite occurs within 10 m of the veins, while hydrothermal pyrite, chalcopyrite and sphalerite all extend to 50 m. Framboidal pyrite possibly greigite. present in unaltered metasediments becomes progressively recrystallised and replaced by hydrothermal pyrite, chalcopyrite and sphalerite as mineralisation is approached. Hydrothermal pyrite is generally euhedral and anomalous in having high As contents when compared to framboidal pyrite. Maximum Au grades 205 ppm. occur in the saddle reef position and below a thick shale unit. Lower-grade mineralisation 0.5–6.0 ppm. occurs above this in the overlying stratigraphy. As and Pb anomalies cross cut the alteration zoning and occur as plume-like dispersion haloes above the mineralisation. The Au occurs in and near the As ‘plume’. Cu concentrations reach their maximum values adjacent to high Au values. Measured CO2 values confirm the observed carbonate distributions. H2Oq and Zn values in the section show relatively random distributions. Two separate stages of mineralisation are indicated, the earlier localised within classic saddle reef structures and containing the highest Au, Cu and some As and a later, cross-cutting stage of mineralisation associated with high As. The alteration is mainly associated with the former. q1998 Elsevier Science B.V. All rights reserved

This report responds to a request by the U.S. Geological Survey (USGS) that the National Research Council (NRC) review its concept of The National Map. The National Map is envisioned by USGS as a database providing “public domain core geographic data about the United States and its territories that other agencies can extend, enhance, and reference as they concentrate on maintaining other data that are unique to their needs” (USGS, 2001).

My adventures as a paleontologist have taken me to many exciting places at home, in the UK, and abroad, and led to the discovery of new species. Working with teams of colleagues, I named the new dinosaurs Eotyrannus, Xenoposeidon, and Mirischia, and the pterosaurs Vectidraco and Eurazhdarcho. One of the things that interests me most about dinosaurs, giant marine reptiles, and other ancient animals is that every one of them has a unique history, just as animals do today.

Whole Earth Geophysics illustrates how different types of geophysical observations provide constraints on Earth’s gross structure and composition. It introduces geology students with a basic grounding in math and physics to the fundamentals of various geophysical techniques, but does not stop there. Specific observations illustrate how each technique constrains certain aspects of the plate tectonic framework that is fundamental to the study of Earth science today.
This book is designed for a Solid Earth Geophysics course at the advanced undergraduate or beginning graduate level. While the primary objective is to illustrate the utility of geophysical observations to geology students, geophysics students may benefit from the book by seeing the basics of their discipline in the context of geology. <...>