What is going on here?

Transcription

1 Major Digression! Atoms? Elements? Compounds? Minerals? Rocks? What is going on here?

2 Carleton College

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5 One Illustrated Helium Atom

6 One Oxygen Atom

7 One Silicon Atom 12 Silicon Atoms

8 Silicon Tetrahedron: the building block of most minerals

9 Nesosilicate: Garnet Fosterite Fayalite Kyanite Olivine Sillimanite Sphene Topaz Zircon Sorosilicate Epidote Zoisite Bertrandite Idocrase

10 Single Chain: Pyroxenes (Augite, Diopside, Enstatite, Jadite)

11 Double Chains: Amphiboles (Hornblende, Riebeckite, Tremolite) A sites may hold K, Na, other large ions M sites may hold Ca, Na, Mn, Fe, Mg, other intermediate ions

12 Cyclosilicate Tourmalines Beryl

13 Phylosilicates Micas Biotite Muscovite Lepidolite Phlogopite Clays Chlorite Clays Kaolinite Pyrophyllite Talc Prehnite Serpentine

14 Aluminum Octahedron: A major component of clay minerals

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16 Magmatism produces these major element averages: Chemical analyses of some representative Igneous Rocks Ultra-Basic Basic Intermed Felsic Intermed Peridotite Basalt Andesite Rhyolite Phonolite SiO TiO Al2O Fe2O FeO MnO MgO CaO Na2O K2O H2O Total This slide from: Petrology/Ch%2008%20Major%20Elements.ppt

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18 Figure Alumina saturation classes based on the molar proportions of Al 2 O 3 /(CaO+Na 2 O+K 2 O) ( A/CNK ) after Shand (1927). Common non-quartzo-feldspathic minerals for each type are included. After Clarke (1992). Granitoid Rocks. Chapman Hall.

19 Sedimentation produces a homogenized range of compositions

20 Clastic Sedimentary Rock Classification: Sandstones, Siltstones, Claystones

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22 Summary of Digression: Atoms-made of protons, electrons, neutrons Elements-differ in number of p, e, n Compounds-made of elements Minerals are compounds-mostly silicates Rocks-made of minerals

23 Magmatism produces these major element averages: Chemical analyses of some representative Igneous Rocks Ultra-Basic Basic Intermed Felsic Intermed Peridotite Basalt Andesite Rhyolite Phonolite SiO TiO Al2O Fe2O FeO MnO MgO CaO Na2O K2O H2O Total ~Mantle Partial Melts of the Mantle This slide from: Petrology/Ch%2008%20Major%20Elements.ppt

24 What is partial melting of the mantle? Incompatible Elements: elements that do not fit well in a mineral structure. During partial melting the incompatible elements move from the solid mineral phase to the newly forming liquid phase. Solid Primitive Mantle 1-compatible element 2-compatible element 3-compatible element 4-incompatible element 5-incompatible element 6-incompatible element Partial Melting Solid Depleted Mantle 1-compatible element 2-compatible element 3-compatible element The Melt 4-incompatible element 5-incompatible element 6-incompatible element

25 Where does partial melting occur? Robb (2005 ) Introduction to Ore Forming Processes

26 Which elements are compatible with each other? Si Fe S The Goldschmidt Classification of Elements

27 The result of magmatism is depletion of the upper mantle due to partial melting AND the enrichment of the crust. We measure depletion and enrichment by comparing element abundances with those of C1 Chrondrite meteorites, which are a proxy for the original Earth before magmatism began.

28 Which elements are compatible with each other? Si Fe S The Goldschmidt Classification of Elements

29 Some Base Metal Ore Models Figure 9-11 Kessler (1994) Mineral Resources, Economics, And the Environment

30 Magmatic Processes Within the magma chamber During magmatic ascent During volcanic venting The role of water Magmatic water Ground water