Abstract

Robust, stratigraphic control and constraints on the timing of events have been established for the Paleoproterozoic metasedimentary and metavolcanic succession that hosts the Broken Hill Pb-Zn-Ag orebody in western New South Wales. Geologically consistent depositional, intrusive, and metamorphic ages are elucidated by means of SHRIMP U-Pb analyses of zircon and integrated field studies. Comparisons of the new SHRIMP results with those of previous studies clarify some previously untenable age interpretations. A range of zircon provenance ages is found in albitic metasedimentary rocks from one of the oldest recognized parts of the Willyama Supergroup (Thackaringa Group). The zircons indicate maximum depositional ages of 1720 to 1730 Ma, and a minimum stratigraphic age for the lower Thackaringa Group is constrained by the 1704 ± 3 Ma intrusive Alma Gneiss. The latter is the same age as gneissic granitoid rocks in the Redan zone (southern Broken Hill Domain: 1703 ± 3, 1705 ± 3 Ma). Felsic magmatism of this age has long been known in the contiguous Olary Domain (South Australia), but has not been recognized previously at Broken Hill. Depositional ages in the Broken Hill Group, the upper part of which hosts the Pb-Zn-Ag orebody, indicate that the entire package was deposited within a period of ca. 10 m.y. An age of 1685 ± 3 Ma for felsic metavolcaniclastic rocks in the Hores Gneiss (spatially and stratigraphically associated with the ore horizon) corroborates previous work. This age is within error of that determined for the hanging-wall and footwall unit (Rasp Ridge Gneiss) of the orebody (1683 ± 3 Ma). It suggests that felsic magmatism in the Rasp Ridge Gneiss was coeval with that of the Hores Gneiss. Previous interpretations, which suggested that the Hores Gneiss is not a single stratigraphic entity but comprises younger intrusions having ages from 1690 to1640 Ma, are not supported by our data and conclusions. The stratigraphic integrity of the Broken Hill Group (excluding some mafic intrusions) is further supported by results from an older formation near its base, where tuffaceous metasedimentary rocks from the Ettlewood Calc-Silicate Member (Allendale Metasediments) define an age of 1693 ± 4 Ma. This is in good agreement with the age of 1693 ± 5 Ma for the immediately overlying Parnell Formation. Provenance ages obtained from detrital zircons in Broken Hill Group psammites indicate a remarkable uniformity of Paleoproterozoic and late-Archean source(s). Generally matching provenance ages are found in the overlying Sundown Group psammopelites, suggesting a stable flux of sediment fill as the basin deepened and matured. Similar provenance is indicated for upper Paragon Group sedimentary rocks, and inherited zircons in most of the younger granitoids have age spectra similar to those of the detrital zircons. The perpetuation of these age patterns, in both clastic detritus and magmatic xenocrysts, thus broadly fingerprints exposed and buried older crustal elements that provided material to produce the Willyama Supergroup basin fill.
Google map showing geographic bounding box with values North bound -28.0 East bound 144.0 West bound 138.0 South bound -32.0
Related Links
For information on acquiring this product,
please contact Geoscience Australia Client Services via:

fax:
+61 2 6249 9960; or
phone:
1800 800 173 (within Australia);
 
+61 2 6249 9966 (outside Australia).

Product Type/Sub Type

dataset - External Publication - Scientific Journal Paper

Constraints

license
Creative Commons Attribution 4.0 International Licence

IP Owner

Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

2005

Product Type

dataset

Topic Category

geoscientificInformation

Keywords

External Publication
Scientific Journal Paper
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Geographic Extent

North bound
-28.0
East bound
144.0
West bound
138.0
South bound
-32.0

Lineage

Unknown

Digital Transfer Options

onLine

Distributor

Role
distributor
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address

Metadata File Identifier

a05f7892-f9d5-7506-e044-00144fdd4fa6

Metadata Standard Name

ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata

Metadata Standard Version

1.1

Metadata Date Stamp

2015-03-23

METADATA SECURITY CLASSIFICATION

unclassified

Metadata Contact

Role
pointOfContact
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address
Related Links
For information on acquiring this product,
please contact Geoscience Australia Client Services via:

fax:
+61 2 6249 9960; or
phone:
1800 800 173 (within Australia);
 
+61 2 6249 9966 (outside Australia).