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Potassic igneous rocks and associated gold–copper mineralization
Lithos 56 Ž2001. 265–266 www.elsevier.nlrlocaterlithos
Book review Potassic igneous rocks and associated gold–copper mineralization By Daniel Muller and David I. Groves, Springer-Verlag Berlin Heidelberg, Germany, 2000. Hardcover, XIII q 252 p., price DM 129.00 Potassic and ultrapotassic rocks occur in various tectonic settings, from converging oceanic and continental margins to cratonic areas. They are really intriguing subjects in igneous petrology and geochemistry because these igneous rocks show a very wide range of chemical composition, with major and trace elements and isotopes from high to extremely enriched particularly trace elements, such as Th, U, Rb, Ba and LREE. Affinity ranges from mildly potassic shoshonitic suites associated with cal-alkaline magmas in arc environments to ultrapotassic leucitites, kamafugites and lamproites. They also have an economic interest, since they may be associated with mineralization and may host precious minerals, such as the case of diamond-bearing lamproites. Attention of petrologists, geochemists and economic geologists have been attracted because of all these factors from many times; however, comprehensive books on these rocks are virtually lacking, whereas many books exist on single aspects. The book by Muller and Groves tries to fill this gap by giving a review of classification, genesis, tectonic settings and economic aspects of potassic rocks, even if the book is much devoted to the latter aspects. The book basically consists of two parts: in the first third ŽChapters 1–4., the authors elucidate the aspects related with nomenclature, tectonic setting and petrogenesis of potassic rocks, and provide a short description of the main type localities from various tectonic settings; in the following two thirds of the book ŽChapters 5–10., the economic aspects are reviewed, placing emphasis on the association of potassic rocks with Au–Cu mineralizations.
After an introductory chapter, chapter 2 reports an overview of definitions, nomenclature of potassic rocks, starting from an historical perspective. This part is particularly short and without figures, that could help readers to unravel the complex nomenclature of potassic rocks. Chapter 3 reports the tectonic setting of potassic rocks; the authors start from the erection of two nested databases to discuss in detail not only the variability of the tectonic settings but also problems connected with discrimination tools of tectonic settings. Chapter 4 reports type-localities of potassic rocks from the five different tectonic settings recognized in chapter 3. Choice of type-localities seems not well done; two examples: the Roman Province as type-locality for continental arcs setting and African Rift valley as type-locality for withinplate setting. There is a large debate if the Roman Province is an example of continental arc or is a post-collisional magmatic province. On the other hand, African Rift valley rocks are not inserted in the databases and this limit the significance of the typelocality. Chapter 5 discusses the significance and genesis of enrichment of precious metal in potassic rocks. There are still controversies on the relative contribution of magmatic versus metamorphic and crustal versus mantle components to the fluids responsible for the origin of precious-metal deposits. The authors report an example that points to a magmatic Žmantle. hypothesis. Chapter 6 present relationships between gold–copper deposits and potassic rocks studying cases, where clear evidence for their direct connection exist, whereas Chapter 7 reports the same relationships when the evidence are not so forceful. A further database is constructed comprehending geochemical data for potassic rocks
0024-4937r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 4 - 4 9 3 7 Ž 0 0 . 0 0 0 6 7 - 0
266
Book reÕiew
from mineralized localities. Chapter 8 contains a short but informative discussion on the behavior of halogens ŽF, Cl. in magmatic systems, and on the role of halogen-rich fluids for the transport of metals in ore deposits related to potassic rocks. A database of micas from mineralized and barren potassic rocks is erected to test their potential as exploration guides. Chapter 9 tries to integrate the petrological, geochemical and tectonic aspects discussed in the previous chapters to explore critically the implications for strategies of mineral exploration, even if shortness of the chapter does not permit to completely reach the goal of the chapter. Chapter 10 consists of 24 tables that report the main characteristics of various gold–copper deposits, with details on type and exact location of mineralization, age and tectonic setting, production and estimated reserves, texture, mineralogy and geochemistry of associated potassic rocks, and ore minerals. References are exhaustive, whereas subject index is a little short of some useful crossreferences. Possibility of having the various databases should have been greatly appreciated by many readers. Shortcomings regard mainly the oversimplification in the assignment of tectonic setting of some areas, the shortness of some chapters that limit the
usefulness of them, and the unbalanced petrologyr economic geology parts. However, academic geoscientists mainly interested in petrogenesis of potassic magmas, after reading this book, surely can better appreciate how many close relations exist between magmatology and economic geology. The above flaws are, hence, of minor importance with respect to the usability of the book. The book is well written and clearly illustrated with many Ž61. well-drawn figures; really useful are the several Ž68. simple and informative tables. All this help the reader to follow author’s line of reasoning very easily. Overall, the book will be an important reference text to scholars and students interested in potassic magmatism, mineralization, igneous petrology and economic geology. Giampiero Poli ) Department of Earth Sciences, UniÕersity of Perugia, 06100 Perugia, Italy E-mail address: [email protected]
)
Corresponding author. Tel.: q39-075-585-2607; fax: q39075-585-2603.
Book review Potassic igneous rocks and associated gold–copper mineralization By Daniel Muller and David I. Groves, Springer-Verlag Berlin Heidelberg, Germany, 2000. Hardcover, XIII q 252 p., price DM 129.00 Potassic and ultrapotassic rocks occur in various tectonic settings, from converging oceanic and continental margins to cratonic areas. They are really intriguing subjects in igneous petrology and geochemistry because these igneous rocks show a very wide range of chemical composition, with major and trace elements and isotopes from high to extremely enriched particularly trace elements, such as Th, U, Rb, Ba and LREE. Affinity ranges from mildly potassic shoshonitic suites associated with cal-alkaline magmas in arc environments to ultrapotassic leucitites, kamafugites and lamproites. They also have an economic interest, since they may be associated with mineralization and may host precious minerals, such as the case of diamond-bearing lamproites. Attention of petrologists, geochemists and economic geologists have been attracted because of all these factors from many times; however, comprehensive books on these rocks are virtually lacking, whereas many books exist on single aspects. The book by Muller and Groves tries to fill this gap by giving a review of classification, genesis, tectonic settings and economic aspects of potassic rocks, even if the book is much devoted to the latter aspects. The book basically consists of two parts: in the first third ŽChapters 1–4., the authors elucidate the aspects related with nomenclature, tectonic setting and petrogenesis of potassic rocks, and provide a short description of the main type localities from various tectonic settings; in the following two thirds of the book ŽChapters 5–10., the economic aspects are reviewed, placing emphasis on the association of potassic rocks with Au–Cu mineralizations.
After an introductory chapter, chapter 2 reports an overview of definitions, nomenclature of potassic rocks, starting from an historical perspective. This part is particularly short and without figures, that could help readers to unravel the complex nomenclature of potassic rocks. Chapter 3 reports the tectonic setting of potassic rocks; the authors start from the erection of two nested databases to discuss in detail not only the variability of the tectonic settings but also problems connected with discrimination tools of tectonic settings. Chapter 4 reports type-localities of potassic rocks from the five different tectonic settings recognized in chapter 3. Choice of type-localities seems not well done; two examples: the Roman Province as type-locality for continental arcs setting and African Rift valley as type-locality for withinplate setting. There is a large debate if the Roman Province is an example of continental arc or is a post-collisional magmatic province. On the other hand, African Rift valley rocks are not inserted in the databases and this limit the significance of the typelocality. Chapter 5 discusses the significance and genesis of enrichment of precious metal in potassic rocks. There are still controversies on the relative contribution of magmatic versus metamorphic and crustal versus mantle components to the fluids responsible for the origin of precious-metal deposits. The authors report an example that points to a magmatic Žmantle. hypothesis. Chapter 6 present relationships between gold–copper deposits and potassic rocks studying cases, where clear evidence for their direct connection exist, whereas Chapter 7 reports the same relationships when the evidence are not so forceful. A further database is constructed comprehending geochemical data for potassic rocks
0024-4937r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 4 - 4 9 3 7 Ž 0 0 . 0 0 0 6 7 - 0
266
Book reÕiew
from mineralized localities. Chapter 8 contains a short but informative discussion on the behavior of halogens ŽF, Cl. in magmatic systems, and on the role of halogen-rich fluids for the transport of metals in ore deposits related to potassic rocks. A database of micas from mineralized and barren potassic rocks is erected to test their potential as exploration guides. Chapter 9 tries to integrate the petrological, geochemical and tectonic aspects discussed in the previous chapters to explore critically the implications for strategies of mineral exploration, even if shortness of the chapter does not permit to completely reach the goal of the chapter. Chapter 10 consists of 24 tables that report the main characteristics of various gold–copper deposits, with details on type and exact location of mineralization, age and tectonic setting, production and estimated reserves, texture, mineralogy and geochemistry of associated potassic rocks, and ore minerals. References are exhaustive, whereas subject index is a little short of some useful crossreferences. Possibility of having the various databases should have been greatly appreciated by many readers. Shortcomings regard mainly the oversimplification in the assignment of tectonic setting of some areas, the shortness of some chapters that limit the
usefulness of them, and the unbalanced petrologyr economic geology parts. However, academic geoscientists mainly interested in petrogenesis of potassic magmas, after reading this book, surely can better appreciate how many close relations exist between magmatology and economic geology. The above flaws are, hence, of minor importance with respect to the usability of the book. The book is well written and clearly illustrated with many Ž61. well-drawn figures; really useful are the several Ž68. simple and informative tables. All this help the reader to follow author’s line of reasoning very easily. Overall, the book will be an important reference text to scholars and students interested in potassic magmatism, mineralization, igneous petrology and economic geology. Giampiero Poli ) Department of Earth Sciences, UniÕersity of Perugia, 06100 Perugia, Italy E-mail address: [email protected]
)
Corresponding author. Tel.: q39-075-585-2607; fax: q39075-585-2603.