alkali granite silica content

References as in Fig. Chappell & White, 1974; Collins et al., 1982; White & Chappell, 1983; King et al., 1997), it is important to see how they fit into our classification (Fig. These rocks are predominantly alkali–calcic and magnesian, although at silica abundances >70% some of these granitoids are calc-alkalic. 1b. The metaluminous rocks tend to have a lower Fe-number, whereas the peraluminous rocks tend to have the higher Fe-number. (a) FeO/(FeO + MgO) vs wt % SiO2. Fax: 307-766-6679. & Erskine, B. A-type n = 67; I-type n = 1155; S-type n = 720. a, alkalic; a-c, alkali–calcic; c-a, calc-alkalic; c, calcic. The chemical reaction can result in abnormal expansion and cracking of concrete. This pressure effect is largely the result of decreases with pressure in the extent of polymerization for all olivine + orthopyroxene-saturated … Furthermore, many granitic systems are demonstrably open to a variety of chemical inputs. The distinctive potassic granites termed A-type by Loiselle & Wones (1979) differ from the granitoids of the Cordilleran batholiths (Fig. In addition to serving as a means of classification, the scheme presented here also provides a means for using major element analyses of granite suites to better understand their origin and evolution. & Bickford, M. E. (, Cullers, R. L., Griffin, T., Bickford, M. E. & Anderson, J. L. (, De la Roche, H., Leterrier, J., Grandclaude, P. & Marchal, M. (, Duchesne, J.-C., Berza, T., Liégeois, J.-P. & Auwera, J. V. (, Ferré, E. C., Caby, R., Peucat, J. J., Capdevila, R. & Monié, P. (, Frost, B. R., Lindsley, D. H. & Andersen, D. J. 10). This arises from the fact that the geochemical compositions of granitic magmas reflect the compositions of their source rocks rather than their tectonic setting (e.g. If one wishes to use a chemical (as opposed to a geographic) term to describe these rocks, it would be better to use ‘calc-magnesian’. a, alkalic; a-c, alkali–calcic; c-a, calc-alkalic; c, calcic. Y��B���?�]�Я�_j_���>5�|�ps�廒��o�k_�' \^��'�Lڱ���B�j������E��4�8�jyf�^�~PG� \��7܀_%p�0�n�ܓλ~�|�VB7\]p�C�W5�& wish to acknowledge NSF grant EAR9706237 for supporting their work on granite petrogenesis, and C.G.B. ��o������™Ӕmk�n�x\�]EbU��lp~[s�C���j��^�e&( 3�R�,����:�c(w��z��4�r΁��_�L�ȉ���sյ�a�s�U"�&\�9�{��?��4.9?��-�����G�/�����w�E�7�1�~��N�І�W2�����Z�k�.>��c5� ��U.��k2�sR{�����y����� v[:�U�7Y^�Ƽo2��V2���6E����q������l�����߄&��\ ����ᩪG�.��Q]v�������C�(s�ʎ��;R�M �5$�B".R��vԖg��s#�Q=��VU�-B�jƽk,������NGå���:��nmwm[K�~a�Y�{�G��n�����ok�׍f��O��%^�b�m4W{ol�_U�ؼ���ڭ7W�5����n~WW�U+�,�ݠ�~����YB�. However, it is possible, perhaps likely, that leucogranitic crustal melts make major contributions to the silica-rich magmas in other settings (Figs 4–6), leading to a significant mixing component in the trends used to define our compositional groupings. iron enrichment in the silicates) during differentiation whereas the relatively oxidized basaltic rocks from arcs do not (Frost & Lindsley, 1991). In contrast, the magnesian series reflects a close affinity to relatively hydrous, oxidizing magmas and source regions (Frost & Lindsley, 1991), which is consistent with origins that are broadly subduction related. In our database, there is a roughly equal proportion of metaluminous and peraluminous rocks. (a) FeOtot/(FeOtot + MgO) vs wt % SiO2 and (b) Na2O + K2O – CaO vs wt % SiO2. The high MALI of Caledonian granites may also have a mantle contribution, because modern analogues of post-tectonic granites, the high-K lavas of the Tibetan plateau, are largely mantle derived (Arnaud et al., 1992; Turner et al., 1996). To avoid this reaction in concrete, the use of low alkali cements is one option or otherwise the use of mineral admixtures is recommended. For example, ferroan granitoids reflect a close affinity to relatively anhydrous, reduced magmas and source regions. In our classification, they are magnesian calcic and calc-alkalic granitoids, though a small number are alkali–calcic (Fig. there are reported cases of alkali-silica reaction related to this kind of aggregates, [1]. The wide range in modified alkali–lime index from peraluminous leucogranites (Fig. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide, This PDF is available to Subscribers Only. It is also possible, however, that differentiation can cause a suite of rocks to become more alkalic. Sources of data: Viljoen & Viljoen (1969), Barton (1975), Hurst et al. (, Frost, B. R., Frost, C. D., Hulsebosch, T. P. & Swapp, S. M. (, Frost, C. D., Frost, B. R., Chamberlain, K. R. & Edwards, B. R. (, Fuhrman, M. L., Frost, B. R. & Lindsley, D. H. (, Gastil, G., Diamond, J., Knaack, C., Walawender, M., Marshall, M., Boyles, C., Chadwick, B. endstream endobj 41 0 obj <> endobj 42 0 obj <>/ExtGState<>/Font<>/ProcSet[/PDF/Text]>>/Rotate 0/TrimBox[4.5 4.5 607.5 787.5]/Type/Page>> endobj 43 0 obj <>stream Data from McDougall (1962). I-type granitoids are dominantly calc-alkalic and calcic; <1% are alkali–calcic. Both S- and I-type are dominantly magnesian, but, like the Mesozoic batholiths of western North America (Fig. 63 0 obj <>/Filter/FlateDecode/ID[<0DA4B16A31CD4F459BBA4E42DB08736C>]/Index[40 43]/Info 39 0 R/Length 105/Prev 420892/Root 41 0 R/Size 83/Type/XRef/W[1 2 1]>>stream Such conditions are common in extensional environments. Thus one explanation for a suite of rocks that cross the trend lines shown in Fig. π@gW���ɩ(����H��눛h�K� �wâ��D�ǧb�WD��t�f�P~Y���S�^}����L&�_��h �P4��,���p��qDwϓ;�ǧ|�w�"���DR�Rq�II7�4���AR?Q.0�s�C�ԥ�H��G�t@��>�� ����3�Q��E�7�ѵ0 ��&��Υ��hL �4��PF94��=_iU�A:��[�`'Ȥ�+�F�}��駻(����Rg:�$}Hx�:���ru!�D߁���� �˰s)� ���gm�s��r)3(�-J�L��������V�MN�h�7ڑ��[����(�ͅC�iRlo�O�[&��g�!BۼR/w㑴�3>U��h,q�:Gǝw�r� �x�A��A'�IaP���}���(;��,EO�4���x�e+���)��W��Rr�Y^��6�U9�x��H�`G����R��OϓJ�jn-]���.��pˆ��W��m��w]o�X�F{/�e���M0 ��Y�O���f���܆�s��o6ѥ�C�y�����o��6a������j 1\J��k���6�O8�|z�1hố�)ʻL�_��8��1�&%1&�Q���q\ލd���9����� �DT@�/tA_��5�h@ÒJt�H�A�3&���葞��h��|�E6a39�r2�0}���Id���QOF�`�af�g�`VZ�-v�J���`�1��A�S(��̠O B., Currie, K. L. & Chappell, B. W. (, Zhao, J.-X., Shiraishi, K., Ellis, D. J. The proposed classification frees granite petrologists to discuss the compositional features of granitic rocks without recourse to either genetic or tectonic preconceptions. Pearce et al., 1984). The composition range for 486 samples from A-type batholiths. The chemical discriminators used here are sensitive indicators of both the source regions of granitic magmas and the differentiation paths followed by these magmas. 5), but they tend to be less iron enriched. In fact, all the ferroan granitoids from Cordilleran suites are peraluminous, as are all the rocks that are alkalic and alkali–calcic. Because of the many papers that have been written on the granitoids of the Lachlan Fold Belt (e.g. $Xv��>&F�� +�N�g � pN E-mail: The late-stage portion of alkalic complexes such as Coldwell complex (Mitchell & Platt, 1978), the Gardar province (Ferguson, 1970), and the Monteregian province (Valiquette & Archambault, 1970) also plot into the ferroan–alkalic field.

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