Chapter 29 Minerals and the Environment

LIST EVERYTHING THAT IS IN A PENCIL

LIST EVERYTHING THAT IS IN TOOTHPASTE

LIST EVERYTHING THAT IS IN A LIGHTBULB

LIST EVERYTHING THAT IS IN MONEY

LIST EVERYTHING THAT IS IN A GLASS

LIST EVERYTHING THAT IS IN PAPER

LIST EVERYTHING THAT IS IN A SIDEWALK

WHAT MINERALS AND HOW MUCH OF EACH WILL YOU LIKELY USE DURING YOUR LIFETIME?

How Mineral Deposits Are Formed Ore Deposits – formed when metals are concentrated in anomalously high amounts by geological processes Mineral resources are usually extracted from ore deposits

ORIGINS OF MINERAL DEPOSITS Nine elements account for about 99% of the earth’s crust by weight. The remainder are found in trace amounts. O 45%; Si 27%; Al 8%, Fe 6%; Ca 5%; Mg 3%, Na 2%, K 2 % titanium (Ti) 1%

ORIGINS OF MINERAL DEPOSITS 1. PLATE BOUNDARIES Metal sulfides are precipitated at divergent boundaries as hot water carries dissolved metals to the surface. Convergent boundaries mobilize metals in the molten rock, distilling and concentrating some such as mercury (Hg).

ORIGINS OF MINERAL DEPOSITS 2. IGNEOUS PROCESSES Ore deposits form when magma cools Heavy sink Light float Hot water --> dissolves --> also concentrates concentration

ORIGINS OF MINERAL DEPOSITS 3. SEDIMENTARY PROCESSES sort by size and weight

ORIGINS OF MINERAL DEPOSITS 4. EVAPORITES when inland oceans evaporate –Marine evaporates (solids)-potassium and sodium salts, gypsum, anhydrite –Nonmarine evaporates (solids)-sodium and calcium carbonate, sulfate, borate, mitrate, and limited iodine and strontium compounds –Brines (liquids derived from wells, thermal springs, inland salt lakes, and seawaters)-bromine, iodine, calcium chloride, and magnesium and sometimes heavy metals such as copper, lead and zinc

ORIGINS OF MINERAL DEPOSITS 5. BIOLOGICAL PROCESSES phosphates and iron some could be formed only when lower oxygen in atmosphere (Gray beds) Calcium minerals of shells and bones 31 different Biologically produced minerals

ORIGINS OF MINERAL DEPOSITS 6. WEATHERING PROCESSES decomposition of rock --> bauxite or aluminum ore

ORIGINS OF MINERAL DEPOSITS 7. OCEAN FLOOR DEPOSITS Hydrothermal vents and divergent plate boundaries --> sulfide deposits with zinc, copper, iron Sea water --> magnesium Ocean floor --> manganese oxide nodules

Secondary enrichment process

Resources and Reserves Minerals are classified as: –1. Mineral Resources Elements, chemical compounds, minerals or rocks that can be extracted to obtain a usable commodity –1. Mineral Reserves The portion of the resource that is identified and from which usable materials can be legally and economically extracted at the time of evaluation

How Much Do We Use?? Metallic Vs. Non-Metallic Sodium and Iron: 100-1,000 million metric tons /year N, S, K, Ca: million metric tons /year Zn, Cu, Al, Pb: 3-10 million metric tons/year Ag, Au: 10,000 metric tons/year

Availability of Mineral Resources When the availability of a mineral becomes limited, there are 4 possible solutions: 1. Find more sources 2. Recycle and reuse what has already been obtained 3. Reduce consumption 4. Find a substitute

Impacts of Mineral Development Environmental Impacts –Depends on many factors – mining procedures, climate, rock type, etc. –Subsurface Vs. Surface mining Social Impacts –Increased demand for housing and services in mining areas –When ore is gone $ is gone and Jobs are gone

Minimizing Environmental Impact of Mineral Development Environmental regulations at the federal, state and local levels Reclaiming Stabilizing soils Controlling air emissions Preventing contaminated water from leaving or treating contaminated water that has left a mining site On-site and off-site treatment of waste Practicing the 3 R’s of waste management

Minerals and Sustainability R-to-C Ratio –A measure of the time available for finding the solutions to depletion of nonrenewable resources –R = known reserves –C = rate of consumption Often misinterpreted as the time a reserve will last at the present rate of consumption. Is a present analysis of a dynamic system in which both the amount of reserves and consumption may change over time.