Earth Systems 3209

1. Earth Systems 3209 Reference: Chapters 21; Appendix A & B Unit: 5Earth’s Resources

2. Unit 5: Topic 1.1 Economic Minerals and Mineral Deposits Focus on . . . • defining economic mineral and ore. • identifying factors which determine if a mineral is of economic value • identifying and describing the different types of mineral deposits.

3. Terminology Associated with Economic Minerals • Economic Minerals • minerals that can be extracted, processed, and marketed at a profit. • Factors: • interest in the mineral • size of the deposit • mineral concentration • mineral depth below the surface • market value. • An Ore is a natural material with a high concentration of economically valuable minerals that can be mined for a profit. Text Reference: Pages 583

4. Origin of Mineral Deposits • A mineral depositis a volume of rock enriched in one or more minerals. In this sense amineral refers to a useful material, a definition that is different from the way we defined amineral earlier in this course. • Mineral deposits can be classified on the basis of the mechanism responsible for concentratingthe valuable substance.Examples Include: • Magmatic Mineral Deposits • Hydrothermal Mineral Deposits • Sedimentary Mineral Deposits • Placer Mineral Deposits • Metamorphic Deposits Text Reference: Pages 583 - 596

5. Magma Chamber Crystal Settling Metallic Mineral Deposits • Magmatic Deposits • Accumulations of metals associated with magma that forms igneous rocks • Certain metals are enriched in certain magmas and further concentrated during cooling of the magma • As minerals crystallize from amagma body, heavy mineralsmaysink to the bottom of themagma chamber and othersmay form on the sides of themagma chamber.

6. Metallic Mineral Deposits • Magmatic Deposits • a) Layered • Gravitational Settling - heavy minerals that crystallize early, settle and concentrate on the bottom of the magma chamber this results in a layered deposit. High-density minerals sink to the bottom of the magma chamber.

7. Metallic Mineral Deposits • Magmatic Deposits • b) Disseminated • A mineral deposit in which the metal is evenly distributed in generally low concentrations throughout large masses of igneous rock. • Ex: porphyry copper deposit • Ex: Nickel deposits. • Sudbury, Ontario and Voisey’s Bay,Newfoundland Labrador A sample of nickel-bearing rock from Sudbury.

8. Metallic Mineral Deposits • 2) Hydrothermal Mineral Deposits • Minerals are concentrated by hot fluidsflowing through fractures and pore spaces in rocks. • Hydrothermal deposits are produced when groundwater circulates down to depths and heats up, either by coming near a hot igneous body or by circulating to great depthswhich naturally heat the water. • Such hot water can dissolve valuable minerals as it passes through alarge volume of rock.

9. Ore minerals depositing in veins Cooler water moving toward surface Hot water moving at depths Metallic Mineral Deposits • 2) Hydrothermal Mineral Deposits • As the hot water moves into cooler areas of the crust, the dissolvedminerals are precipitated and deposited from the hot water solution. • If the cooling takes place rapidlyin open fractures or upon reaching cool surface waters, thenprecipitation will take place over a limited area, resulting in a higher concentration of minerals than was originally present in the rocks. • Example: Vein deposits

10. Metallic Mineral Deposits • Hydrothermal Mineral Deposits • Black Smokers

11. Metallic Mineral Deposits • Hydrothermal Mineral Deposits • Note:In the diagram to theright both vein depositsand disseminateddeposits are seensurrounding themagma chamber.

12. Metallic Mineral Deposits • 3) Placer Deposits • Formed when heavy metals are mechanically concentrated by flowing surface waters depositing high density minerals eitherin streams or along coastlines. • When the velocity of the water slows, minerals with a higherdensity are deposited. Heavy minerals like gold, diamond, and magnetite will be concentrated in areas where water current velocity is low. The lighter minerals (quartz) are carried away. • Examples: Gold, Platinum, Diamonds

13. 1) between ripple marks 2) behind rock bars PlacerDeposit PlacerDeposit PlacerDeposit Stream Direction Stream Direction Stream Direction 3) on the inside of meandering streams 4) in holes on the bottom of a stream PlacerDeposit Metallic Mineral Deposits • Placer Deposits • Placer deposits occur in any areawhere current velocity is low, such as;

14. Metallic Mineral Deposits • Placer Deposits • Placer deposits occur in any areawhere current velocity is low, such as; • formed when heavy metals aremechanically concentrated bycurrents • Examples: • Gold, Platinum, Diamonds

15. Metallic Mineral Deposits • Secondary Enrichment (Sedimentation) • These deposits often form as a result of chemical weathering in warm tropical climates that receive high temperatures and high amounts of rainfall which produces highly leached soils rich in both iron and aluminium. Chemical weathering tends to remove the soluble materials, leaving the less soluble residues. • Two common mineral deposits formed in this wayareiron-rich Limonite and aluminium-rich Bauxite.Bauxite is the world’s primary source of aluminium.It forms in rainy tropical climates from chemical weathering.

16. Metallic Mineral Deposits • Secondary enrichment (Sedimentation) • In addition, an existing mineral deposit can be turned in to a more highly concentratedmineral deposit by weathering in a process called secondary enrichment.

17. Metallic Mineral Deposits • 5) Metamorphic Deposits • Many of the most important metamorphic ore deposits are produced by contact metamorphism. Skarns are metal-rich deposits in Carbonate rocks that has undergone contact metamorphism.

18. Non-Metallic Resources • Diamonds • Most diamonds are found in unique ultramafic igneous rocks called kimberlites. • Magma generated by partial melting of asthenosphere below 150 kilometres and then rises quickly to the surface, picking up diamonds from solid lithospheric mantle.

19. Kimberlite Pipes and Diamonds Non-Metallic Resources

20. Example 1: D C Which letter represents a location in the river wherea placer deposit would most likely form. Explain tworeasons to support your choice. Answer: Letter “C” represents the only location along the river where a placer deposit would most likely form. In a meandering river, current velocities differ from inside of turns to outside of turns. The current velocity of water, at location “C”, is slower on the inside of turns and faster on the outside of turns, location “B”. Placer deposits usually involve high density and/or heavy materials, for example, gold. Because it takes energy and/or high velocity (fast-moving) water to transport gold, then it is only appropriate to look for gold along areas of a river (e.g. location C) where the energy and/or current velocity is low. A B

21. Example 2: Which process produces copper mineralization in veins around granitic intrusions? (A) Hydrothermal (B) Layered magmatic (C) Metamorphism (D) Placer Based on the statement below, Which is the correct match between mineral and rock type? Mineral Rock Type (A) diamond gabbro (B) diamond kimberlite (C) gold gabbro (D) gold kimberlite Beneath a circular lake is a carrot-shaped deposit of ultramafic composition.

22. Your Turn . . . Take the time and complete the following questions . . .(Solutions to follow) Questions: Indicate the type of mineral deposit which could form at location A and explain the process.

23. Solutions . . . Questions:Indicate the type of mineral deposit which could form at location A and explain the process. Answer:Hydrothermal (or vein) is the type of mineral deposit that could form at location A. Pressure from the magma intrusion causes fractures or cracks to form in the overlying sedimentary rock layers. Ground water in the overlying sedimentary rock layers is warmed by the heat that is radiating out from the magma intrusion. Warm water can dissolve large quantities of elements. As the warm water, which is enriched in elements, flows toward Earth’s surface (away from the magma intrusion) through fractures or cracks, it begins to cool. Since cold water cannot dissolve elements as readily as warm water, minerals begin to precipitate out of the solution. These minerals are found in the fractures or cracks forming hydrothermal vein deposits.

24. Summary . . . Overview of Points covered: • Economic Mineral - minerals that can be extracted, processed, and marketed at a profit. • Ore - natural material with a high concentration of economically valuable minerals that can be mined for a profit. • 5 Types of Mineral Deposits Include: • Magmatic Mineral Deposits 4) Placer Mineral Deposits • Hydrothermal Mineral Deposits 5) Metamorphic Deposits • Sedimentary Mineral Deposits