Archean Rare-Metal Pegmatites in Zimbabwe and Western Australia: Geology and Metallogeny of Pollucite Mineralisations

ISBN-13: 9783030109424 / Angielski / Miękka / 2019 / 125 str.

Thomas Dittrich; Thomas Seifert; Bernhard Schulz

Spis treści

1 Introduction

1.1 Motivation and Scope of the Thesis

1.2 Structure of the Thesis

2 Geological Settings of Archean Cratons 

2.1 Yilgarn Craton

2.1.1 Tectonostratigraphic Framework and Geological Development

2.1.2 Tectonic Models for the Development 

2.1.3 Pegmatites within the Yilgarn Craton 

2.1.4 Geological setting of the Londonderry Pegmatite Field 

2.1.5 Geological Setting of the Mount Deans Pegmatite Field

2.1.6 Geological Setting of the Cattlin Creek Pegmatite Deposit

3 Fieldwork and Sampling of Selected Pegmatites and Pegmatite Fields

3.1 Londonderry Pegmatite Field 

3.1.1 Londonderry Feldspar Quarry Pegmatite 

3.1.2 Lepidolite Hill Pegmatite

3.1.3 Tantalite Hill Pegmatite 

3.2 Mount Deans Pegmatite Field

3.2.1 Type I – Flat Lying Pegmatites 

<3.2.2 Type II – Steeply Dipping Pegmatites

3.3 Cattlin Creek Pegmatite

4 Petrography and Mineralogy

4.1 Quantitative Mineralogy by Means of Mineral Liberation Analysis

4.2 Mineralogical and Petrographical Characteristics of Individual Mineral Groups 

4.2.1 Feldspar 

4.2.2 Quartz

4.2.3 Mica

4.2.4 Petalite

5 Geochemistry

5.1 Major Elements

5.2 Selected Minor and Trace Elements

5.3 Fractionation Indicators

5.4 Rare Earth Elements 

6 Geochronology 

6.1 40Ar/39Ar-Method on Mica 

6.1.1 Mount Deans Pegmatite Field

6.1.2 Londonderry Pegmatite Field

6.1.3 Cattlin Creek Pegmatite 

6.1.4 Wodgina Pegmatite

6.2 Th-U-Total Pb Monazite Dating 

6.2.1 Monazite Ages

6.3 U/Pb Dating of Selected Ta-, Nb- and Sn-Oxide Minerals

6.3.1 Londonderry Pegmatite Field 

6.3.2 Mount Deans Pegmatite Field

6.3.3 Cattlin Creek Pegmatite

6.3.4 Wodgina Pegmatite

7 Stable and Radiogenic Isotopes 

7.1 Whole Rock Sm/Nd-Isotopy

7.1.1 New Whole Rock Sm/Nd Data 

Blurb

Lithium-cesium-tantalum (LCT) pegmatites are important resources for rare metals. For Cs, only the LCT pegmatites with the zeolite group mineral pollucite at Bikita (Zimbabwe Craton) and Tanco (Superior Province Craton) are of commercial importance. Common characteristics of world-class LCT pegmatite deposits include their Meso- to Neoarchean age and geological setting within greenstone belt lithologies on Archean Cratons.

This study presents the first coherent and comparative scientific investigation of five major LCT pegmatite systems from the Yilgarn, Pilbara and Zimbabwe Craton. For the evaluation of their Cs potential and of the genetic concepts of pollucite formation, the pegmatites from Wodgina, Londonderry, Mount Deans and Cattlin Creek were compared to the Bikita pollucite mineralization. 

The integration of the new data (e.g., geochronological and radiogenic isotope data) into the complex geological framework: 1) enhances our knowledge of the formation of LCT pegmatite systems, and 2) will contribute to the further exploration of additional world-class LCT pegmatite deposits, which 3) may host massive pollucite mineralisations.