研究夏威夷地函擄獲岩中斜輝石稀土元素(REE)含量變化可對板內岩石圈地函化學組成及動力學提供良好制約。本研究利用離子探針對斜輝石進行系統性單點分析，分析來自夏威夷歐胡島(Oahu Island) Pali脈中尖晶石二輝橄欖岩，結果可將稀土元素含量變化分成三種: (1)輕稀土元素(LREE)貧瘠配分模式，通常可視為部份熔融後之殘餘固體；(2)U型稀土元素配分模式，以及(3)輕稀土元素富集配分模式；後兩種配分模式代表夏威夷地函擄獲岩受到與輕稀土元素富集之流體反應(Sen et al., 1993; Yang et al., 1998)；分析擄獲岩中同位素含量指示與Honolulu火山活動來源一致(Vance et al., 1989; Okano and Tatsumoto, 1996; Lassiter et al., 2000; Ducea et al., 2002; Bizimis et al., 2003; 2007)。對於U型稀土元素配分模式產生機制，本研究提出三種流體與橄欖岩作用，包括礦物內元素擴散作用、流體與橄欖岩混何結果、以及一維流體滲透模型。斜輝石中中心至邊緣濃度由低增高趨勢必然由礦物內擴散作用造成，計算後得知至少需5000－8000年造成，此結果與鈾系估計岩漿經產生至噴發時間不符合(< 800 年；Sims et al., 1999)。斜輝石與鹼性矽質流體不同比例混何結果亦無法滿足分析所得之U型配分模式；因此，U型稀土元素配分模式必然是與富集輕稀土元素之流體於上部地函橄欖岩反應產生之結果，換言之，顯示擄獲岩來自受到地函交代換質作用之上部地函。利用流體滲透模型對斜輝石中稀土元素進行模擬，可將元素間視為離子交換反應並表示成對時間與距離之函數，模擬結果發現大尺度與區域尺度下，流體滲透模型皆可得到最佳化稀土元素配分模式。在大尺度滲透模型下，流體以每年10公分流速、孔隙率0.5 %條件下，方向為由下往上流經地函10公里距離，經50000年反應時間，可得樣本77PAII-10-cpx1的最佳化U型配分模式。假設流速上升至每年數百公分，則流體可能以通道流(channel flow)形式存在於夏威夷上部地函；在每年以1公分流速下，孔隙率維持0.5 %，流體在區域尺度(100公尺)滲透模型下，滲透時間為12000年，樣本77PAII-10-cpx1亦可得最佳化模擬結果，此區域尺度流體滲透模型指示流體普遍存在於夏威夷上部地函。對於兩種模型，依據岩象與溫壓推估結果，本研究較贊成大尺度流體滲透模型。

Mantle chemical dynamics is an important link to understand element cycling in solid Earth. Profound variations in the REE patterns of clinopyroxene from the Oahu spinel lherzolite xenoliths provide an opportunity for investigating chemical dynamics in the intra-plate lithospheric mantle. Core-to-rim variations in REE abundances of clinopyroxene grains were determined by in-situ ion probe analysis. REE variations in clinopyroxene from the Pali spinel lherzolite xenoliths were classified into three types: (1) LREE-depleted patterns typical of melting residues, (2) U-shaped REE patterns, and (3) nearly-flat REE and slight LREE-enriched patterns. The U-shaped and flat REE patterns were typically attributed to interaction between LREE-depleted melting residues and LREE-enriched melts (Sen et al., 1993; Yang et al., 1998). The Sr-Nd-Os-Hf-Pb isotope data of these xenoliths indicate involvement of Honolulu Volcanics (Vance et al., 1989; Okano and Tatsumoto, 1996; Lassiter et al., 2000; Ducea et al., 2002; Bizimis et al., 2003; 2007). Three major types of melt-peridotite interactions have been proposed, including: (1) simple element diffusion from melt into peridotite (Klugel, 1998; Van Orman et al., 2001), (2) mixing between melt and peridotite (Song and Frey, 1989), and (3) melt percolating through peridotite (e.g., Takazawa et al., 1992; Ionov et al., 2002; 2006). However, simple element diffusion during transportation of peridotitic xenoliths to surface by magmas results in core-to-rim REE concentration gradients higher than that in our samples, while mixing between peridotite and alkalic siliceous melts does not show intensive concave down patterns of the samples. Therefore, REE patterns of the samples must be dominated by processes prior to incorporation of the xenoliths into their host lavas. The “melt percolation model” that simulates exchange of trace elements between melt and matrix solid as a function of time and distance from melt entrance provides satisfactory explanation for the observed U-shaped patterns. Modeling results indicate that both large-scale and local-scale melt percolation processes can cause the U-shaped REE patterns of clinopyroxene in the Pali lherzolitic xenoliths. Large-scale porous flow percolation (~10 km) with rapid melt velocity (~20 cm/yr) and a porosity of ~0.5 % may produce U-shaped REE patterns satisfactorily fitting to that of analyzed clinopyroxene (77PAII-10-cpx1) with percolation time of 50000 years. The reaction time can be reduced to several thousand years, if the melt velocity increases to several meters per year. In such a case, the channel flow should once occur in the upper mantle beneath Oahu, Hawaii. An alternative model is that the U-shaped REE patterns were resulted from local-scale porous flow prevalently occurring in the upper mantle. With a melt velocity of 1 cm/yr and a porosity of ~0.5 %, strong zonation REE pattern in 77PAII-10-cpx1 could be produced over relatively short distances of ~100 m by local-scale porous flow coupled with short time interval (~12000 yr). This inference must be confirmed by more analyses on clinopyroxene for LREE abundances and robust constraints on the equilibrium depths of the xenoliths.

Anders, E., and N. Grevesse, Abundances of the elements: Meteoritic and solar Geochemica et Cosmochimica Acta, 53, 197-214, (1989)
Asimow, P. D., et al., An analysis of variations in isentropic melt productivity, Philosophical Transactions of the Royal Society of London Series a-Mathematical Physical and Engineering Sciences, 355, 255-281, (1997)
Bailey, D.K., Volatile flux, heat focusing and generation of magma, Geol. J. Spec., 177-186, (1970)
Bailey, D.K., Uplift, rifting and magmatism in continental plates, Journal of Earth Sciences, 225-239, (1972)
Bear, J., Dynamics of Fluids in Porous Media, American Elsevier, New York, 764 pp. (1972)
Bedini, R. M., et al., Evolution of LILE-enriched small melt fractions in the lithospheric mantle: a case study from the East African Rift, Earth and Planetary Science Letters, 153, 67-83, (1997)
Beenson, M. H., and E. D. Jackson, Origin of the garnet pyroxenite xenoliths at Salt Lake Crater, Oahu., Mineral Soc., 3, 95-112, (1970)
Bizimis, M., et al., Ancient recycled mantle lithosphere in the Hawaiian plume: Osmium-Hafnium isotopic evidence from peridotite mantle xenoliths, Earth and Planetary Science Letters, 257, 259-273, (2007)
Bizimis, M., et al., Hf-Nd isotope decoupling in the oceanic lithosphere: constrains from spinel peridotites from Oahu, Hawaii, Earth and Planetary Science Letters, 217, 43-58, (2003)
Bizimis, M., et al., Hf-Nd-Sr isotope systematics of garnet pyroxenites from Salt Lake Crater, Oahu, Hawaii: Evidence for a depleted component in Hawaiian volcanism, Geochimica et Cosmochimica Acta, 69, 2629-2646, (2005)
Blundy, J., and J. Dalton, Experimental comparison of trace element partitioning between clinopyroxene and melt in carbonate and silicate systems, and implications for mantle metasomatism, Contributions to Mineralogy and Petrology, 139, 356-371, (2000)
Bodinier, J.-L., et al., Mechanisms of mantle metasomatism: geochemical evidence from the Lherz orogenic peridotite, J. Petrol, 31, 597-628, (1990)
Bodinier, J.-L., et al., Silicate, hydrous and carbonate metasomatism at Lherz, France: contemporaneous derivatives of silicate melt-harzburgite reaction, J. petrol, 45, 299-320, (2004)
Clague D.A. and Dalrymple G.B., The Hawaiian-Emperor volcanic chain: Part 1. Geologic evolution. In: R.W. Decker, T.L. Wright and P.H. Stauffer, Editors, Volcanism in Hawaii, Vol. 1, U.S. Geol. Surv. Prof. Pap. 1350, pp. 5–54 (1987)
Clague, D. A., and F. A. Frey, Petrology and Trace-Element Geochemistry of the Honolulu Volcanics, Oahu - Implications for the oceanic mantle below Hawaii, Journal of Petrology, 23, 447-504, (1982)
Crank, J., The mathematics of diffusion, Oxford University Press, New York, 414 pp. (1975)
Dawson, J. B., Contrasting types of upper-mantle metasomatism?, Kimberlites-II. The Mantle and Crust / Mantle Relationships, edited by J. Kornprobst, pp. 290-294, (1984)
de Marsily, G., Quantitative Hydrogeology: Groundwater Hydrology for Engineers, Academic press, London, 440 pp. (1986)
Doell, R. R., and Dalrympl. G. B., Potassium-Argon Ages and Paleomagnetism of Waianae and Koolau Volcanic series, Oahu-Hawaii, Geological Society of America Bulletin, 84, 1217-1241 (1973)
Ducea, M., et al., Melt depletion and subsequent metasomatism in the shallow mantle beneath Koolau volcano, Oahu (Hawaii), Geochemistry Geophysics Geosystems, 3 (2002)
Fick, A., On liquid diffusion, Phil. Mag. and Jour. Sci., 10, 31-39, (1855)
Franz, L., et al., Reequilibration of ultramafic xenoliths from Namibia by metasomatic processes at the mantle boundary, Journal of Geology, 104, 599-615 (1996)
Frey, F. A., The Origin of Pyroxenites and Garnet Pyroxenites from Salt-Lake Crater, Oahu, Hawaii - Trace-Element Evidence, American Journal of Science, 280, 427-449 (1980)
Frey, F. A., and Clague, D. A., Geochemistry of Diverse Basalt Types from Loihi Seamount, Hawaii - Petrogenetic Implications, Earth and Planetary Science Letters, 66, 337-355 (1983)
Frey, F. A., and Green, D. H., The mineralogy, geochemistry and origin of lherzolite inclusions in Victorian basanites, Geochimica et Cosmochimica Acta, 38, 1023-1059 (1974)
Frezzotti, M. L., and Peccerillo, A., Diamond-bearing COHS fluids in the mantle beneath Hawaii, Earth and Planetary Science Letters, 262, 273-283 (2007)
Godard, M., et al., Effects of Mineralogical Reactions on Trace-Element Redistributions in Mantle Rocks During Percolation Processes - a Chromatographic Approach, Earth and Planetary Science Letters, 133, 449-461 (1995)
Griselin, M., and J. C. Lassiter, Extreme unradiogenic Os isotopes in Hawaiian mantle xenoliths: implications for mantle convection, Geochimica et Cosmochimica Acta, 66, A292-A292 (2002)
Hart, S. R., and T. Dunn, Experimental cpx/melt partitoning of 24 trace elements Contrib. Mineral. Petrol, 113, 1-8 (1993)
Harte, B., Chloritoid-Staurolite Assemblages in Central Perthshire, Geological Magazine, 117, 615-616 (1980)
Harte, B., Mantle peridotites and processes-the kimberlite sample, in Continental Basalts and Mantle Xenoliths, edited by C. J. Hawkesworth and M. J. Morry, Cheshire, Engl: Shiva, pp. 46-91 (1983)
Hauri, E. H., Melt migration and mantle chromatography, 1: simplified theory and conditions for chemical and isotopic decoupling, Earth and Planetary Science Letters, 153, 1-19 (1997)
Hauri, E. H., and S. R. Hart, Constraints on Melt Migration from Mantle Plumes - A Trace-Element Study of Peridotite Xenoliths from Savaii, Western-Samoa, Journal of Geophysical Research-Solid Earth, 99, 24301-24321 (1994)
Henderson, P., et al., Structural Controls and Mechanisms of Diffusion in Natural Silicate Melts, Contributions to Mineralogy and Petrology, 89, 263-272 (1985)
Hirose, K., and I. Kushiro, Partial Melting of Dry Peridotites at High-Pressures - Determination of Compositions of Melts Segregated from Peridotite Using Aggregates of Diamond, Earth and Planetary Science Letters, 114, 477-489 (1993)
Ionov, D. A., et al., Mechanisms and sources of mantle metasomatism: major and trace element compositions of peridotite xenoliths from Spitsbergen in the context of numerical modeling, J. Petrol 43, 2219-2259 (2002)
Ionov, D. A., et al., Trace element distribution in peridotite xenoliths from Tok, SE Siberian craton: A record of pervasive, multi-stage metasomatism in shallow refractory mantle, Geochimica et Cosmochimica Acta, 70, 1231-1260 (2006)
Iwamori, H., Dynamic Disequilibrium Melting Model with Porous Flow and Diffusion-Controlled Chemical Equilibration, Earth and Planetary Science Letters, 114, 301-313 (1993b)
Iwamori, H., A Model for Disequilibrium Mantle Melting Incorporating Melt Transport by Porous and Channel Flows, Nature, 366, 734-737 (1993a)
Iwamori, H., et al., Melt Generation by Isentropic Mantle Upwelling, Earth and Planetary Science Letters, 134, 253-266 (1995)
Jackson, E. D., and T. L. Wright, Xenoliths in Honolulu Volcanic Series, Hawaii, Journal of Petrology, 11, 405-430 (1970)
Johnson, K. T. M., Experimental determination of partition coefficients for rare earth and high-field strength elements between clinopyroxene, garnet and basaltic melt at high pressures, Contributions to Mineralogy and Petrology, 133, 60-68 (1998)
Johnson, K. T. M., et al., Melting in the oceanic upper mantle: an ion microprobe study of diopsides in abyssal peridotites, J. Goeophys. Res., 95, 2661-2678 (1990)
Kelemen, et al., Extraction of MORB from the mantle by focused flow of melt in dunite channels, Nature, 375, 747 – 753 (1995)
Kelemen, P. B., et al., Formation of harzburgite by pervasive melt/rock reaction in the upper mantle, Nature, 385, 635-641 (1992)
Kempton, P. D., et al., Petrography, petrology and geochemistry of xenoliths and megacrysts from Geronimo volcanic field, south eastern Arizona, in Kimberlites II: The Mantle and Crust-Mantle Relationships, edited by J. Kornprobst, Amsterdam: Elsevier, pp. 71-84 (1984)
Keshav, S., et al., Tholeiitic to alkalic transition in basaltic liquids: Some inferences from high-pressure garnet-pyroxenite melting, Geochimica et Cosmochimica Acta, 67, A212-A212 (2003)
Keshav, S., and G. Sen, A rare composite xenolith from Salt Lake Crater, Oahu: high-pressure fractionation and implications for kimberlitic melts in the Hawaiian mantle, Contributions to Mineralogy and Petrology, 144, 548-558 (2003)
Keshav, S., and G. Sen, The depth of magma fractionation in the oceanic mantle: Insights from garnet-bearing xenoliths from Oahu, Hawaii, Geophysical Research Letters, 31 (2004)
Klein, E. M. L., C.H., Global correlations of ocean ridge basalt chemistry with axial depth and crustal thickness, Journal of Geophysical Research, 92, 8089-8115 (1987)
Klugel, A., Reactions between mantle xenoliths and host magma beneath La Palma (Canary Islands): constraints on magma ascent rates and crustal reservoirs, Contributions to Mineralogy and Petrology, 131, 237-257 (1998)
Langmuir, C. H., Klein, E. M. & Plank, T., Petrological systematics of mid-ocean ridge basalts: constraints on melt generation beneath ocean ridges. In: Phipps Morgan, J., Blackman, D. K. & Sinton, J. M. (eds) Mantle Flow and Melt Generation at Mid-Ocean Ridges. American Geophysical Union Monograph 71, 183–280 (1992)
Lanphere, M. A., and G. B. Dalrymple, Age and Strontium Isotopic Composition of the Honolulu Volcanic Series, Oahu, Hawaii, American Journal of Science, 280, 736-751 (1980)
Lassiter, J. C., et al., Generation of Hawaiian post erosional lavas by melting of a mixed lherzolite/pyroxenite source, Earth and Planetary Science Letters, 178, 214-228 (2000)
McKenzie, D., The Generation and Compaction of Partially Molten Rock, Journal of Petrology, 25, 713-765 (1984)
McKenzie, D., The Extraction of Magma from the Crust and Mantle, Earth and Planetary Science Letters, 74, 81-91 (1985)
Mercier, J. C. C., et al., Equilibrium State of Diopside-Bearing Harzburgites from Ophiolites - Geobarometric and Geodynamic Implications, Contributions to Mineralogy and Petrology, 85, 391-403 (1984)
Moore, J. G., et al., Diverse Basalt Types from Loihi Seamount, Hawaii, Geology, 10, 88-92 (1982)
Mukasa, S. B., and H. G. Wilshire, Isotopic and trace element compositions of upper mantle and lower crustal xenoliths, Cima volcanic field, California: Implications for evolution of the subcontinental lithospheric mantle, Journal of Geophysical Research-Solid Earth, 102, 20133-20148 (1997)
Navon, O., and E. Stolper, Geochemical consequeneces of melt percolation: the upper mantle as a chromatographic column, J. Geol., 95, 285-307 (1987)
Nielson, J. E., and H. G. Wilshire, Magma Transport and Metasomatism in The Mantle - A Critical-Review of Current Geochemical Models, American Mineralogist, 78, 1117-1134 (1993)
O’Hara, M. J., Are Ocean Floor Basalts Primary Magma, Nature, 220, 683-686 (1968)
Okano, O. and Tatsumoto, M., Petrogenesis of ultramafic xenoliths from Hawaii inferred from Sr, Nd, and Pb isotopes. Earth Processes: Reading the Isotopic Code. Geophysical Monograph, American Geophysical Union, 95: 135-147 (1996)
Ozawa, K., Mass balance equations for open magmatic systems: Trace element behavior and its application to open system melting in the upper mantle Journal of Geophysical Research-Solid Earth, 106, 13,407 - 413,434 (2001)
Ozawa, K., and N. Shimizu, Open-system melting in the upper mantle: Constraints from the Hayachine-Miyamori ophiolite, northeastern Japan, Journal of Geophysical Research-Solid Earth, 100, 22,315 - 322,335 (1995)
Pike, J. E. N., and E. C. Schwarzman, Classification of Textures in Ultramafic Xenoliths, Journal of Geology, 85, 49-61 (1977)
Plank, T., and Langmuir, C.H., Effects of the melting regime on the composition of the oceanic crust, Journal of Geophysical Research, 97, 19749-19770 (1992)
Salters, V. J. M., and A. Zindler, Extreme Hf-176/Hf-177 in the sub-oceanic mantle, Earth and Planetary Science Letters, 129, 13-30 (1995)
Sen, G., A pertologic model for the constitution of the upper mantle and crust of the Koolau shield, Oahu, Hawaii, and Hawaiian magmatism, Earth and Planetary Science Letters, 63, 215-228 (1983)
Sen, G., Fractionation Processes in Deccan Traps Magmas - Reply, Journal of Petrology, 28, 239-240 (1987)
Sen, G., Petrogenesis of spinel lherzolite and pyoxenite suite xenoliths from the Koolau shield, Oahu, Hawaii: Implications for petrology for the post eruptive lithosphere beneath Oahu, Contrib. Mineral. Petrol, 100, 61-91 (1988)
Sen, G., et al., Evolution of the lithosphere beneath Oahu, Hawaii: an ion probe investigation of mantle xenoliths, Earth and Planetary Science Letters, 62, 53-69 (1993)
Sen, G., et al., Hawaiian mantle xenoliths and magmas: Composition and thermal character of the lithosphere, American Mineralogist, 90, 871-887 (2005)
Sen, G., and W. P. Leeman, Iron-Rich Lherzolitic Xenoliths from Oahu - Origin and Implications for Hawaiian Magma Sources, Earth and Planetary Science Letters, 102, 45-57 (1991)
Sen, G., and D. C. Presnall, Petrogenesis of Dunite Xenoliths from Koolau Volcano, Oahu, Hawaii - Implications for Hawaiian Volcanism, Journal of Petrology, 27, 197-217 (1986)
Sen, G., et al., Anomalous isotopes and trace element zoning in plagioclase peridotite xenoliths of Oahu (Hawaii): implications for the Hawaii plume, Earth and Planetary Science Letters, 207, 23-38 (2003)
Shaw, C. S. J., Effects of melt viscosity and silica activity on the rate and mechanism of quartz dissolution in melts of the CMAS and CAS systems, Contributions to Mineralogy and Petrology, 151, 665-680 (2006)
Shaw, C. S. J., and D. B. Dingwell, Experimental peridotite-melt reaction at one atmosphere: a textural and chemical study, Contributions to Mineralogy and Petrology, 155, 199-214 (2008)
Shaw, C. S. J., and A. D. Edgar, Post-entrainment mineral-melt reactions in spinel peridotite xenoliths from Inver, Donegal, Ireland, Geological Magazine, 134, 771-779 (1997)
Sims, K. W. W., et al., Porosity of the melting zone and variations in the solid mantle upwelling rate beneath Hawaii: Inferences from U-238-Th-230-Ra-226 and U-235-Pa-231 disequilibria, Geochimica et Cosmochimica Acta, 63, 4119-4138 (1999)
Skulski, T., et al., High-Pressure Experimental Trace-Element Partitioning between Clinopyroxene and Basaltic Melts, Chemical Geology, 117, 127-147 (1994)
Sleep, N. H., et al., Onset of Mantle Plumes in the Presence of Preexisting Convection, Journal of Geophysical Research-Solid Earth and Planets, 93, 7672-7689 (1988)
Song, Y., and F. A. Frey, Geochemistry of Peridotite Xenoliths iIn Basalt from Hannuoba, Eastern China - Implications for Subcontinental Mantle Heterogeneity, Geochimica et Cosmochimica Acta, 53, 97-113 (1989)
Spera, F. J., Carbon-Dioxide in Petrogenesis .3. Role of Volatiles in the Ascent of Alkaline Magma with Special Reference to Xenolith-Bearing Mafic Lavas, Contributions to Mineralogy and Petrology, 88, 217-232 (1984a)
Stehfest, H., Algorithm 368: Numerical inversion of Laplace transforms Communications of ACM, 13, 44-49 (1970a)
Stehfest, H., Remark on algorithm 368: Numerical inversion of Laplace transforms, Communications of ACM, 13, 624 (1970b)
Takazawa, E., et al., Geochemical Evidence for Melt Migration and Reaction in the Upper Mantle, Nature, 359, 55-58 (1992)
Van Orman, J. A., et al., Rare earth element diffusion in diopside: influence of temperature, pressure, and ionic radius, and an elastic model for diffusion in silicates, Contributions to Mineralogy and Petrology, 141, 687-703 (2001)
Vance, D., et al., He, Sr And Nd Isotopes in Xenoliths from Hawaii and other Oceanic Islands, Earth and Planetary Science Letters, 96, 147-160 (1989)
Vasseur, G., Vernieres, J. and Bodinier, J.L., Modeling of trace element transfer between mantle melt and heterogranular peridotite matrix, Journal of Petrology Special Volume: 41-54 (1991)
Vernieres, J., et al., A plate model for the simulation of trace element fractionation during partial melting and magma transport in the Earth's upper mantle, J. Geophys. Res., 102, 24771-24784 (1997)
Wal, D. V. d., and Bodinier, J.-L., Origin of the recrystallisation front in the Ronda peridotite by km-scale pervasive porous melt flow Contributions to Mineralogy and Petrology, 122, 387-405 (1996)
White, R.W., Ultramafic inclusion in basaltic rocks from Hawaii contributions to Mineralogy and Petrology, 12: 245-314 (1966)
Wilshire, H.G. and Shervais, J.W., Physics and Chemistry of Earth, 9. Pergamon Press, 257-272 pp (1975)
Wirth, R., and A. Rocholl, Nanocrystalline diamond from the Earth's mantle underneath Hawaii, Earth and Planetary Science Letters, 211, 357-369 (2003)
Xu, Y.-G., et al., Melt percolation and reaction atop a plume: evidence from the poikiloblastic peridotite xenoliths from Borée (Massif Central, France) Contributions to Mineralogy and Petrology, 132 (1998)
Yang, H. J., et al., Constraints on the source components of lavas forming the Hawaiian north Arch and Honolulu volcano, J. Petrol .Geol, 44, 603-627 (2003)
Yang, H. J., et al., Mid ocean ridge melting: Constraints from lithospheric xenoliths at Oahu, Hawaii J. Petrol. 39, 277-295 (1998)
Zanetti, A., Vannucci, R., Bottazzi, P., Oberti, R. and Ottolini, L., Infiltration metasomatism at Lherz as monitored by systematic ion-microprobe investigations close to a hornblendite vein. Chemical Geology, 134(1-3): 113-133 (1996)