Authigenic silicate minerals and the magnesium budget in the oceans

1977 ◽  
Vol 286 (1336) ◽  
pp. 273-281 ◽  
Keyword(s):  
Experimental Study ◽  
Clay Minerals ◽  
Temperature Stability ◽  
Geothermal Area ◽  
Removal Rates ◽  
Relative Stabilities ◽  
Silicate Minerals ◽  
Calculated Temperature ◽  
Sheet Silicates ◽  
Excess Mg

The relative stabilities of authigenic Fe-rich and Mg-rich components in sheet silicates are considered for reactions of ( a ) clay minerals undergoing anoxic diagenesis; and ( b ) the montmorillonite phase formed by basalt-seawater interaction. For reaction ( a ) coexisting pyrite and a Mg(OH) 2 component of the silicate are close to equilibrium with aMg2+ in pore fluids (Δ G = - 0.29 kcal/mol; - 1.2 kJ/mol) and the excess Mg 2+ present approximates to that added by diffusion from overlying seawater. Reaction ( b ) can be represented by a mixture of ferroan nontronite and talc components and the calculated temperature/stability relationship agrees with mineralogical zoning in the Reykjanes geothermal area. At T = 523 K the Mg-rich component is dominant and aMg2+ is reduced to 1.7 x 10 -5 (cf. 1.35 x 10 -2 in seawater). Data from an experimental study at 473 K give the result a talc ≈ 0.2. Flux calculations give removal rates of Mg from the oceans of 0.06 x stream supply for reaction ( a ) and 0.6-1.7 x stream supply for reaction ( b ).

Experimental Study of Typical Graded Asphalt Mixture about Dynamic Stability at High Temperature

2016 ◽  
Vol 858 ◽  
pp. 300-304
Author(s):  
Zhen Fu Chen ◽  
Dan Wu ◽  
Qiu Wang Tao ◽  
Yuan Chu Gan
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
High Temperature ◽  
Asphalt Mixture ◽  
Temperature Stability ◽  
Specimen Thickness ◽  
High Temperature Stability ◽  
Change Trend ◽  
Comparison And Analysis ◽  
The Stability

The high temperature stability of AC-16, AC-13, AC-20 under specimen thickness of 5cm and 6cm is studied through indoor asphalt mixture high rutting test, Through comparison and analysis about experimental data, it is found that the stability of AC-16, AC-13, AC-20 asphalt mixture at high- temperature decreases in turn. It is shown that thickness changes did not affect the change trend of the high temperature stability under gradation change, and the stability of AC-16 at high-temperature is the best, the AC-13 is second and the AC-20 is less.

scholarly journals A structure hierarchy for silicate minerals: sheet silicates

2018 ◽  
Vol 83 (1) ◽  
pp. 3-55 ◽  
Author(s):  
Frank C. Hawthorne ◽  
Yulia A. Uvarova ◽  
Elena Sokolova
Keyword(s):  
Double Layer ◽  
Structural Connectivity ◽  
Single Layer ◽  
Common Species ◽  
Two Dimensional ◽  
Structural Units ◽  
Coordination Polyhedra ◽  
Silicate Minerals ◽  
Sheet Silicates ◽  
Sheet Silicate

AbstractThe structure hierarchy hypothesis states that structures may be ordered hierarchically according to the polymerisation of coordination polyhedra of higher bond-valence. A hierarchical structural classification is developed for sheet-silicate minerals based on the connectedness of the two-dimensional polymerisations of (TO4) tetrahedra, where T = Si4+ plus As5+, Al3+, Fe3+, B3+, Be2+, Zn2+ and Mg2+. Two-dimensional nets and oikodoméic operations are used to generate the silicate (sensu lato) structural units of single-layer, double-layer and higher-layer sheet-silicate minerals, and the interstitial complexes (cation identity, coordination number and ligancy, and the types and amounts of interstitial (H2O) groups) are recorded. Key aspects of the silicate structural unit include: (1) the type of plane net on which the sheet (or parent sheet) is based; (2) the u (up) and d (down) directions of the constituent tetrahedra relative to the plane of the sheet; (3) the planar or folded nature of the sheet; (4) the layer multiplicity of the sheet (single, double or higher); and (5) the details of the oikodoméic operations for multiple-layer sheets. Simple 3-connected plane nets (such as 63, 4.82 and 4.6.12) have the stoichiometry (T2O5)n (Si:O = 1:2.5) and are the basis of most of the common rock-forming sheet-silicate minerals as well as many less-common species. Oikodoméic operations, e.g. insertion of 2- or 4-connected vertices into 3-connected plane nets, formation of double-layer sheet-structures by (topological) reflection or rotation operations, affect the connectedness of the resulting sheets and lead to both positive and negative deviations from Si:O = 1:2.5 stoichiometry. Following description of the structural units in all sheet-silicate minerals, the minerals are arranged into decreasing Si:O ratio from 3.0 to 2.0, an arrangement that reflects their increasing structural connectivity. Considering the silicate component of minerals, the range of composition of the sheet silicates completely overlaps the compositional ranges of framework silicates and most of the chain-ribbon-tube silicates.

scholarly journals A structure hierarchy for silicate minerals: chain, ribbon, and tube silicates

2020 ◽  
Vol 84 (2) ◽  
pp. 165-244 ◽  
Author(s):  
Maxwell C. Day ◽  
Frank C. Hawthorne
Keyword(s):  
Repeat Unit ◽  
Structural Connectivity ◽  
The Other ◽  
Silicate Minerals ◽  
One Dimensional ◽  
Compositional Range ◽  
Repeat Units ◽  
Sheet Silicates ◽  
Sheet Silicate ◽  
Connectivity Degree

AbstractA structure hierarchy is developed for chain-, ribbon- and tube-silicate based on the connectedness of one-dimensional polymerisations of (TO4)n− tetrahedra, where T = Si4+ plus P5+, V5+, As5+, Al3+, Fe3+, B3+, Be2+, Zn2+ and Mg2+. Such polymerisations are described by a geometrical repeat unit (with ng tetrahedra) and a topological repeat unit (or graph) (with nt vertices). The connectivity of the tetrahedra (vertices) in the geometrical (topological) repeat units is denoted by the expression cTr (cVr) where c is the connectivity (degree) of the tetrahedron (vertex) and r is the number of tetrahedra (vertices) of connectivity (degree) c in the repeat unit. Thus cTr = 1Tr12Tr23Tr34Tr4 (cVr = 1Vr12Vr23Vr34Vr4) represents all possible connectivities (degrees) of tetrahedra (vertices) in the geometrical (topological) repeat units of such one-dimensional polymerisations. We may generate all possible cTr (cVr) expressions for chains (graphs) with tetrahedron (vertex) connectivities (degrees) c = 1 to 4 where r = 1 to n by sequentially increasing the values of c and r, and by ranking them accordingly. The silicate (sensu lato) units of chain-, ribbon- and tube-silicate minerals are identified and associated with the relevant cTr (cVr) symbols. Following description and association with the relevant cTr (cVr) symbols of the silicate units in all chain-, ribbon- and tube-silicate minerals, the minerals are arranged into decreasing O:T ratio from 3.0 to 2.5, an arrangement that reflects their increasing structural connectivity. Considering only the silicate component, the compositional range of the chain-, ribbon- and tube-silicate minerals strongly overlaps that of the sheet-silicate minerals. Of the chain-, ribbon- and tube-silicates and sheet silicates with the same O:T ratio, some have the same cVr symbols (vertex connectivities) but the tetrahedra link to each other in different ways and are topologically different. The abundance of chain-, ribbon- and tube-silicate minerals decreases as O:T decreases from 3.0 to 2.5 whereas the abundance of sheet-silicate minerals increases from O:T = 3.0 to 2.5 and decreases again to O:T = 2.0. Some of the chain-, ribbon- and tube-silicate minerals have more than one distinct silicate unit: (1) vinogradovite, revdite, lintisite (punkaruaivite) and charoite have mixed chains, ribbons and/or tubes; (2) veblenite, yuksporite, miserite and okenite have clusters or sheets in addition to chains, ribbons and tubes. It is apparent that some chain-ribbon-tube topologies are favoured over others as of the ~450 inosilicate minerals, ~375 correspond to only four topologically unique graphs, the other ~75 minerals correspond to ~46 topologically unique graphs.

Generating functions for stoichiometry and structure of single- and double-layer sheet-silicates

2015 ◽  
Vol 79 (7) ◽  
pp. 1675-1709 ◽  
Author(s):  
Frank C. Hawthorne
Keyword(s):  
Long Range ◽  
Double Layer ◽  
Generating Functions ◽  
Single Layer ◽  
Two Dimensional ◽  
Layer Silicate ◽  
Silicate Minerals ◽  
Topological Features ◽  
Sheet Silicates ◽  
Sheet Silicate

AbstractTwo-dimensional nets may be used to generate the stoichiometry and structure of single-layer and double-layer sheet-silicate minerals. Many sheet-silicate minerals are based on the 3-connected plane nets 63, 4.82, (4.6.8)2(6.82)1and (52.8)1(5.82)1, and some more complicated nets, e.g. (5.6.7)4(5.72)1(62.7)1, (4.122)2(42.12)1, (52.8)1(5.62)1(5.6.8)2(62.8)1,have one or two representative structures. Many complicated sheet-silicate minerals are based on sheets of 2-, 3- and 4-connected tetrahedra that may be developed from 3- and 4-connected plane nets by a series of oikodoméic operations on 3- or 4-connected nets that change the topologyof the parent net. There are three classes of oikodoméic operations: (1) insertion of 2- and 3-connected vertices into 3- and 4-connected plane nets; (2,3) replication of single-layer sheets by topological mirror or two-fold-rotation operators, and condensation of the resulting twosingle-layer sheets to form double-layer sheets. The topological aspects of these sheet structures may be described by functions that express stoichiometry in terms of tetrahedron connectivities (formula-generating functions) and functions that associate these formula-generating functionswith specific two-dimensional nets. Using these functions, we may generate formulae and structural arrangements of single-layer and double-layer silicate structures with specific local and long-range topological features.

Experimental study of the selective adsorption of heavy metals onto clay minerals

2000 ◽  
Vol 19 (2) ◽  
pp. 105-109 ◽  
Author(s):  
Hongping He ◽  
Jiugao Guo ◽  
Xiande Xie ◽  
Jinlian Peng
Keyword(s):  
Heavy Metals ◽  
Experimental Study ◽  
Clay Minerals ◽  
Selective Adsorption
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