Sedimentary Materials - University of Vermont

Sedimentary Materials - University of Vermont

Oxides - Oxyhydroxides FeOOH minerals Goethite or Limonite (FeOOH) important alteration products of weathering Fe-bearing minerals Hematite (Fe2O3) primary iron oxide in Banded Iron Formations Boehmite (AlOOH) primary mineral in bauxite ores (principle Al ore) which forms in tropical soils Gibbsite (Al(OH)3) common Al oxide forming in aqueous sysems Mn oxides form Mn nodules in the oceans (estimated they cover 10-30% of the deep Pacific floor) Many other oxides important in metamorphic rocks Al oxides

Aluminum occurs in economic deposits principally as bauxite Bauxite is a mixture of Al oxides and oxyhydroxides: Diaspore - AlO(OH) Gibbsite - Al(OH)3 Bhmite - AlO(OH) Al is a residual phase and bauxite occurs where weathering is extreme and thick layers of aluminum oxyhydroxide are left over Aluminum concentration controlled by pH-dependent mineral solubility 2

0 Gibbsite -4 Al +++ - -6 Al(OH)4

-8 ++ 2 3 4 5 6

+ ++ + AlOH Al(OH)2 -10 Diagram Al , T = 25 C, P = 1.013 bars, a [H2 O] = 1 log a Al +++ -2

25oC 7 pH 8 9 10 11 12

Greg Mon Nov 01 2004 6 Muscovite Quartz 7 Amorphous silica Activity diagram showing the stability relationships among some

minerals in the system K2O-Al2O3-SiO2-H2O at 25C. The dashed lines represent saturation with respect to quartz and amorphous silica. log (aK+/aH+) 5 K-feldspar 4 3 Gibbsite Kaolinite

2 1 Pyrophyllite 0 -6 -5 -4 -3

log aH SiO 0 -2 -1 Mn oxides - oxyhydroxides Mn exists as 2+, 3+, and 4+; oxide minerals are varied, complex, and hard to ID Wad soft (i.e. blackens your fingers), brown-black fine-grained Mn oxides Psilomelane hard (does not blacked fingers) grayblack botroyoidal, massive Mn oxides XRD analyses do not easily distinguish different minerals, must combine with TEM, SEM, IR

spectroscopy, and microprobe work Mn Oxide minerals (not all) Romanechite

Pyrolusite Ramsdellite Nsutite Hollandite Cryptomelane Manjiroite

Coronadite Todorokite Lithiophorite Chalcophanite Birnessite Vernadite Manganite Groutite Feitknechtite Hausmannite Bixbyite Pyrochroite Manganosite Ba.66(Mn4+,Mn3+)5O10*1.34H2O Psilomelane

MnO2 MnO2 Mn(O,OH)2 Bax(Mn4+,Mn3+)8O16 Kx(Mn4+,Mn3+)8O16 Nax(Mn4+,Mn3+)8O16 Pbx(Mn4+,Mn3+)8O16 (Ca,Na,K)X(Mn4+,Mn3+)6O12*3.5H2O LiAl2(Mn2+Mn3+)O6(OH)6 ZnMn3O7*3H2O (Na,Ca)Mn7O14*2.8H2O MnO2*nH2O MnOOH MnOOH MnOOH

Mn2+Mn23+O4 Mn2O3 Mn(OH)2 MnO Wad Iron Oxides Interaction of dissolved iron with oxygen yields iron oxide and iron oxyhyroxide minerals 1st thing precipitated amorphous or extremely fine grained (nanocrystaliine) iron oxides called ferrihydrite

Fe2+ O2 Ferrihydrite Ferrihydrite (Fe5O7OH*H2O; Fe10O15*9H2O some argument about exact formula) a mixed valence iron oxide with OH and water Goethite Ferrihydrite recrystallizes into Goethite (FeOOH) There are other polymorphs of iron oxyhydroxides: Lepidocrocite -FeOOH Akaganeite -FeOOH

Iron Oxides Hematite (Fe2O3) can form directly or via ferrihydrite goethite hematite Red-brown mineral is very common in soils and weathering iron-bearing rocks Magnetite (Fe3O4) Magnetic mineral of mixed valence must contain both Fe2+ and Fe3+ how many of each?? Spinel structure 2/3 of the cation sites are octahedral, 1/3 are tetrahedral Banded Iron Formations (BIFs) HUGE PreCambrian

formations composed of hematite-jasper-chalcedony bands Account for ~90% of the worlds iron supply Occur only between 1.9 and 3.8 Ga many sites around the world Hammersley in Australia, Ishpeming in Michigan, Isua in Greenland, Carajas in Brazil, many other sites around the world BIFs and bacteria Early earth did not have free O2, as microbial activity

became widespread and photosynthetic organisms started generating O2, the reduced species previously stable (without the O2) oxidized for Fe this results in formation of iron oxide minerals Sulfide Minerals Minerals with S- or S2- (monosulfides) or S22- (disulfides) as anionic group Transition metals bonded with sulfide anion groups Sulfides Part 1 Substitution into sulfides is very common As and Se substitute for S very easily Au can substitute in cation sites

(auriferrous minerals) Different metals swap in and out pretty easily Cu and Fe for instance have a wide range of solid solution materials Complexes Minerals Metals in solution are coordinated with ligands (Such as H2O, Cl-, etc.) Formation of a sulfide mineral requires direct bonding between metals and sulfide requires displacement of these ligands and deprotonation of the sulfide Molecular Clusters are the intermediates between aqueous species and nanocrystals

Sphalerite Wurtzite Structures Zn3S3(H2O)6 aggregation with or without excess bisulfide affects the structure of the resulting nanoscale cluster 5 Zn3S3 (H2O)6 + 3 HS- 3 Zn4S6 (H2O)4 4- + 3 sphalerite structure Zn(H2O)62+ + 3 H+ 2 Zn3S3 (H2O)6 Zn6S6 (H2O)9 + 3 H2O wurtzite structure Pyrite [001] face Iron Sulfides

Pyrite FeS2 (cubic) Marcasite FeS2 (orthorhombic) Troilite FeS end member Pyrrhotite Fe1-xS (slightly deficient in iron) how is charge balance maintained?? Greigite, Mackinawite FexSy Arsenopyrite FeAsS Chalcopyrite CuFeS2 Other important sulfides

Galena PbS Sphalerite/wurtzite ZnS Cinnabar HgS Molybdenite MoS Covellite CuS Chalcocite Cu2S Acanthite or Argenite AgS Stibnite Sb2S3

Orpiment As2S3 ; Realgar AsS Sulfides are reduced minerals what happens when they contact O2? This is the basis for supergene enrichment and acidic mine drainage Actively Oxidizing Pyrite FeS2 + 3.5 O2 + H2O Fe2+ + 2 SO42- + 2 H+ FeS2 + 14 Fe3+ + 8 H2O 15 Fe2+ + 2 SO42- + 16 H+ 14Fe2+ + 3.5 O2 + 14H+ 14 Fe3+ + 7 H2O Sulfur species and H+ generation: FeS2 + 2 Fe3+ 3 Fe2+ + S8 + 0 H+ FeS2 + 7 Fe3+ + 3 H2O 8 Fe2+ + 0.5 S4O62- + 6 H+

AMD neutralization Metals are soluble in low pH solutions can get 100s of grams of metal into a liter of very acidic solution HOWEVER eventually that solution will get neutralized (reaction with other rocks, CO2 in the atmosphere, etc.) and the metals are not so soluble but oxidized S (sulfate, SO42-) is very soluble A different kind of mineral is formed!

Recently Viewed Presentations

  • BPR - DePaul University

    BPR - DePaul University

    A major change in the organization, including structure, culture, and compensation schemes (deepest). BPR Process A process is set of logically related tasks performed to achieve a defined business outcome A collection of activities that, taken together, create value for...
  • CS 4 this week Hw #10 due 4/11

    CS 4 this week Hw #10 due 4/11

    There's madness in this method! Methods. Functions. d.has_key( 1991 ) are functions that are . called by the data itself! has_key( 1991, d ) all data must be passed in as function inputs… are called on their own… Warning: this...
  • Tipos de almacenamiento - M. en I. Ulises Mercado Valenzuela

    Tipos de almacenamiento - M. en I. Ulises Mercado Valenzuela

    Almacenamiento convencional. Medios de movimiento de cargas. Medios de almacenamiento. Tipo de ubicaciones. Características. Casos de aplicación. Almacenamiento de alta densidad. Medios de movimiento de cargas. Medios de almacenamiento. Tipo de ubicaciones.
  • Chapter 6 An Introduction To Metabolism

    Chapter 6 An Introduction To Metabolism

    Chapter 6 An Introduction To Metabolism Metabolism/Bioenergetics Metabolism: The totality of an organism's chemical processes; managing the material and energy resources of the cell Catabolic pathways: degradative process such as cellular respiration; releases energy Anabolic pathways: building process such as...
  • What is a Census?  A count of people

    What is a Census? A count of people

    What is a Census? A count of people and households in the U.S. Helps decision-making in governments and communities. TALKING POINTS. What is a Census?
  • Emerged Technologies Signaling System Seven - SS7

    Emerged Technologies Signaling System Seven - SS7

    Emerged Technologies Signaling System Seven - SS7 Nirmala Shenoy Information Technology Department Rochester Institute of Technology Signaling System 7 Purpose A Signaling Network Exclusively Telephone networks Can be used for ISDN Setting up and clearing call Providing special services Can...
  • CPS 216: Advanced Database Systems

    CPS 216: Advanced Database Systems

    CPS 216: Advanced Database Systems Shivnath Babu Minor Change to Course Logistics Grading: Project 40% 35% Homework Assignments 15% Midterm 20% 25% Final 25% Presentation & Report on "Big Data" 6 topics, 2 students per topic.
  • Behavioral Health Prevention and Early Intervention Mental Health

    Behavioral Health Prevention and Early Intervention Mental Health

    (INSERT STORY) PEI is specifically intended to outreach and engage individuals and communities to educate them on early signs of a mental illness and/or identifying risks of developing a mental illness later on in life.