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  • 1
    Electronic Resource
    Electronic Resource
    A new method of material balance evaluation in metamorphic differentiated systems (1977)
    Springer
    Contributions to mineralogy and petrology 65 (1977), S. 101-110 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The methods used by earlier workers for evaluating material balance in core-mantle-matrix type differentiated systems are examined in detail. It is demonstrated that these methods can be successfully employed only when the true core-mantle volume ratio is known. On geometric grounds, it is rarely possible to have a reliable estimate of this ratio from natural specimen. Consequently, the scope of balance evaluation by these methods is severely restricted. From theoretical consideration of mass transfer relations in differentiated systems, a new computational method is proposed that can be effectively employed for quantitative balance evaluation without any prior knowledge of the core-mantle volume ratio provided the chemical analyses of the core, mantle and matrix are available. This method involves the application of the following mass balance equation: $$m_1 x_1^i + m_2 x_2^i = m_0 x_0^i {\text{ (}}i = {\text{1,2}}...{\text{,}}n{\text{)}}$$ where m 1 and m 2 are the mass of the core and mantle respectively, m 0 is the mass of the matrix involved in differentiation, and x 1 i , x 2 i , x 0 i are the weight fractions of the component i in the core, mantle and matrix respectively. This method would also permit a quantitative estimation of the materials added to or removed from the system. Three differentiated systems previously investigated by Mehnert (1951, 1968), Loberg (1963) and Kretz (1966) are selected for balance evaluation by the proposed method and the results are compared with the published balance analyses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373575
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  • 2
    Electronic Resource
    Electronic Resource
    Regional metamorphism of pelitic rocks around Kandra, Singhbhum, Bihar (1967)
    Springer
    Contributions to mineralogy and petrology 16 (1967), S. 210-232 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract A suite of pelitic rocks around Kandra, Singhbhum District, Bihar, displays a metamorphic gradient registered by the index minerals chlorite, biotite, garnet, staurolite and sillimanite in a Barrovian sequence. Metamorphism was by and large coeval with folding movements, and correlating the internal fabric of minerals and deformational characters, a regular sequence of the index minerals is derived. It is argued that the chronological order by itself is not sufficient to prove that metamorphism was progressive in time. Among the index minerals, garnet appears to have formed by the reaction chlorite+biotitea+quartz ⇌ garnet+biotiteb+H2O. For the origin of sillimanite, a new reaction, 3 staurolite+muscovite+quartz=7 sillimanite+biotite+3H2O, is suggested on the basis of significant textural features. Textural and petrological indications regarding the formation of staurolite are in discordance. Staurolite was either derived from the biotite zone phases, or should be taken to have formed, against textural evidences, from chloritoids of the garnet zone. Graphical analysis of the assemblages by Thompson's ‘AFM’ projection reveals that chlorite and staurolite are excess phases owing to retrogression and incomplete reaction. Shifting of apices of triangular fields and intersection of garnet-biotite tie lines within a zone can be satisfactorily explained in terms of extra components CaO and MnO or their ratios. It is pointed out that if MgO/(MgO + FeO) between two phases show a linear relation, their tie lines will be concurrent on the AF side of the projection, the point of concurrence reflecting equilibrium and temperature of recrystallisation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371093
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    Paper (German National Licenses)
    Fulltext
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