VOI. 41 NO. 2 SCIENCE IN CHINA (Series D) April 1998 Thermal structure and rheology of upper mantle beneath Zhejiang Province, China * LIN C h u a n ~ o n g($$I$%)', SHI ~anbin(*Z%$)', HANXiuling ($$%@)', CHEN Xiaode ( %$@$)I and ZHANG Xiao' ou (!jEtt/J\@)' (1. Institute of Geology, State Seismological Bureau, Beijing 100029, China; 2. Institute of Geology, Chinese Academy of Sciences, Beijing 100029, China) Received October 8, 1997 Abstract The paleogeotherm derived from spinel and garnet lherzolites xenoliths for the upper mantle beneath Zhe- jiang Province, China is higher than the oceanic geotherm but is similar to the geotherm for the upper mantle beneath eastern China constructed by Xu et al. and the upper mantle geotherm of southeastern Australia. The crust-mantle boundary defined by this geotherm is about 34 km, while the lithosphere-asthenosphere boundary is about 75 km. This result coincides well with geophysical data. The study of rheological features of the xenoliths has revealed that at least two periods of deformation events occurred in the upper mantle beneath this reglon. The first event might be related to upper mantle diapir occurring in this region before or during late Tertiary, and the second might be related to the oc- currence of small-scale shear zones in the upper mantle. Keywords: mantle xenolith, upper mantle geotherm, rheology of upper mantle, Zhejiang Province. Thermal state and structure of the upper mantle are the critical data for understanding the structure and dynamics of the lithosphere, and even for its 3-dimensional or 4-dimensional map- ping[l-31 . The detailed study of mantle xenoliths may provide not only the data for constructing the thermal structure of the upper mantle but also the data for understanding its rheology. In Zhejiang Province there is a large areal distribution of Cenozoic basalts, most of which contain mantle xenoliths of both spinel and garnet lherzolite compositions. Therefore, it is an ideal locali- ty for studying the above-mentioned topic. The main purpose of this paper is to get insight into the thermal structure and rheology of the upper mantle beneath this region. The samples studied were collected from the Cenozoic basalts at Caijiawan, Xinchang City and Xilong, Quzhou City. The former is Shenxian Group basalts widely outcropped in Shenxian and Xinchang area. The age of the basalts was used to be assigned to Pliocene epoch[41. Recently, however, Liu et al. have pointed out that the basalts in this region can be classified into early Miocene (having K-Ar age of 2 0 . 7 Ma) and late Miocene to early Miocene (having K-Ar age of . 10.38-4.77 ~ a[51 ) The Xilong basalt appears as a small elliptical pipe of nepheline basalt, 200 m in length and 50 m in width. The age of this basalt is considered to be comparable to Shenxian Group. A detailed study of the petrology and geochemistry of mantle xenoliths from Xilong basalt has been carried out by several author^'^,^], but the xenoliths from Xinchang basalts were poorly reported only in some papers, and a preliminary study has been carried out by the present authors In r e ~ e n t l y ' ~ ] . previous study, however, no complete and reliable upper mantle geotherm for this region can be accepted, because of the relatively small amount of samples studied and the * Project supported by the National Natural Science Foundation of China (Grant No. 49472105) 172 SCIENCE IN CHINA (Series D) Vol. 41 unreliability of the geothermobarometers used for the study. Moreover, the rheology of the upper mantle has not been studied in detail. 1 Rock type and basic features of xenoliths Mantle xenoliths in Xilong basalt have been classified in previous papers into three types as spinel lherzolite, garnet lherzolite and olivine pyroxenite. It was found that most of the garnet lherzolite xenoliths here contain a small amount of spinel. Most of our samples are garnet lherzo- lite except one (ZXL-2) with a small amount of spinel. Mantle xenoliths from Xinchang basalt comprise mainly spinel lherzolite, garnet lherzolite and a small amount of spinel pyroxenite. The basic features of the xenoliths are comparable to those of the Xilong xenoliths, and especially the garnet in garnet lherzolite from both localities has been altered and exhibits pink color, but the chemical compositions of the core of the grain can still be used to estimate the equilibrated temper- ature and pressure[6-83 . The textures of the xenoliths can be classified into protogranular (coarse granular), porphy- roclastic, tabular equigranular and the transition between these textures. The porphyroclastic tex- ture is most common in xenoliths from the studied region, while tabular equigranular texture is relatively rare, indicating that the xenoliths were subjected to deformation process to different ex- tent under upper mantle conditions. The dislocation substructures of olivine from the xenoliths have been revealed by using the oxidation decorating technique. T h e observation has shown that the dislocation substructures of o- livine here are similar to those of xenoliths elsewhere in eastern China. They include dislocation tilt wall, dislocation loops and subgrain structures typical of high-temperature dislocation creep. However, some dislocation substructures representative of high strain rate event such as slip band and those representative of lower temperature plastic deformation such as dislocation tangle have also been found. All these may indicate that the xenoliths from this region experienced relatively complicated deformation history. 2 Estimation of equilibrium temperature and pressure of xenoliths 2.1 Selection of geotherrnometers and geobarometers More than 20 geothermometers and geobarometers have been proposed for calculating the e- quilibrium temperature and pressure of xenoliths. Recently, Brey and ~ o h l e r ' ~ ] assessed ex- have isting geotherrnometers, while XU['O] has tested 17 existing geotherrnometers by using experimen- tal data of natural system. Their results have shown that the two pyroxene geothermometers pro- posed by Bertrand and Mercier['" are the most reasonable geothermometer at present, while the calibrated geothermometer of Nickel et al. [ I 2 ] is also suitable for temperature estimation of natural mantle xenolith. In this paper we used these two geothermometers for temperature estimation of the xenoliths. In addition, a comparison has been carried out by using geotherrnometers common- ly used in previous papers. Pressure estimation of garnet lherzolite has been carried out by using Wood' s[l3] and Nickel and Green's[14' geobarometers, which were commonly used in current references. As for pressure estimation of spinel lherzolite, the single pyroxene geobarometer proposed by ~ e r c i e r " ~ ]which , was widely used in previous papers, has recently been considered unreliable. Recently a geo- barometer suitable for spinel lherzolite has been proposed by Kohler and re^''^] based on calcium No. 2 THERMAL STRUCTURE & RHEOLOGY O F UPPER MANTLE 173 e exchange between olivine and ~ l i n o p ~ r o x e n It. is an only geobarometer that can be used for pres- sure estimation of spinel lherzolite so far, although it has not been widely accepted. We used this geobarometer in the present paper for pressure estimation of spinel lherzolite. The results of esti- mation are listed in table 1. Table 1 Physical parameters for the upper mantle beneath Zhejiang Province derived from spinel and garnet lherzolites xenoliths -- No. T/C P/GPa Z/km oo/GPa ol/GPa io/s-' r)olPa.s- ' E1/s-I r)l/Pa.s-l ZXC37 ZXC-38 ZXC-36 ZXC-55 ZXL-22 ZXC-35 ZXL-25 ZXG 13 ZXL-11 ZXL- 15 ZXC-8 ZXC-52 ZXG12 ZXL-5 ZXC-7 ZXL-16 ZXC-46 1 124 1.95 63 0.014 0.063 8.633 X lo-'' 5.405 x loZo 1.063 x lo-'' 1.976 x 1019 ZXG48 1128 1.89 61 0.010 0.049 3.607X10-'' 5. 9 . 2 4 1 ~ 1 0 ~ ~8 3 2 ~ 1 0 - l 3 2 . 8 0 1 ~ 1 0 ' ~ ZXC-22 1134 1.95 63 0.014 0.075 1 . 2 0 9 X 1 0 ~ ~ ' 3.861X10Z0 2.599X10-l2 9 . 6 1 8 X 1 0 ' ~ ZXC20 1 135 1.95 63 0.013 0.085 9.858 x lo-'' 4.396 x loz0 4.012 x lo-'' 7.063 x 1018 ZXC-1 1 141 2.11 68 0.010 0.063 4.331 x lo-'' 7.696~ loz0 1 . 5 6 5 1 0 1 2 1 . 3 4 2 1019 ~ ~ ZXC-16 1141 2.11 68 . 0.013 0.080 1 . 0 0 3 ~ 1 0 ' ~4 . 3 2 1 ~ 1 0 ~3~ 3 6 1 x 1 0 - ' ~ 7 . 9 3 3 ~ 1 0 ~ ' ZXC-43 1143 2.20 71 0.010 0.051 4 . 1 7 8 ~ lo-'' 7.978~ loz0 7 . 6 7 7 ~ 2.214~ 1019 ZXC-50 1146 2.28 73 1. ~ 0.012 0.064 7 . 5 5 2 ~ 1 0 - " 5 . 2 9 6 ~ 1 0 ~1~. ~ 6 0 1 x 1 0 ~ ~ 3 3 2 ~ 1 0 ' ~ ZXC-33 1 148 2.13 62 0 , 0 1 2 0.061 9.563 x l o i 4 4 . 1 8 2 ~ lo2' 1.739~ 1 . 1 6 9 1019 ~ ZXC-41 1150 1.96 64 0.014 0.061 2 . 0 2 7 ~ 1 0 - ' ~ 2 . 3 0 2 ~ 1 0 ~2~. 2 5 1 ~ 1 0 ~ '9~. 0 3 3 ~ 1 0 ' ~ ZXL-2 1 151 1.88 62 0.009 0.042 5 . 5 7 6 ~ 0 " 1 5.380~ loz0 7 . 7 1 2 ~ 0 - l 3 1 1 . 8 1 5 1019 ~ ZXC-9 1151 1.96 64 0.012 0.075 1 . 2 7 9 ~ 1 0 - ' ~ 3 . 1 2 8 ~ 1 0 ~4~ 5 0 5 ~ 1 0 - ' ~ 5 . 5 5 0 ~ 1 0 ' ~ . ZXC-42 1 153 2.17 70 0.012 0.057 1.077 x 1 0 1 4 3 . 7 1 4 ~ lo2' 1 . 5 7 6 lo-'' ~ 1.205 x 1019 ZXN-8 1177 2.30 74 0.010 ' . 0.048 1 . 1 2 5 X 1 0 - ' ~ 2 . 9 6 2 ~ 1 0 ~1~. 7 0 3 ~ 1 0 ~ 9 ~ 3 9 4 ~ 1 0 ' ~ ZXN-20 1197 2.40 77 0.012 0.044 3 . 3 8 0 ~ 1 0 - ' ~ 1 . 1 8 3 x 1 0 ~ ~2 . 1 6 0 x 1 0 - ~ ~ 6 . 7 8 7 x 1 0 ' ~ ZXL-10 1235 2.38 76 0.010 0.040 6 . 0 6 9 ~ 1 0 - ' ~ 5 . 4 9 9 ~ 1 0 ' ~ 5 . 1 1 9 ~ 1 0 - ' ~ 2 . 6 0 4 ~ 1 0 ' ~ ZXL-19 1238 2.40 77 0.011 0.037 8.791X10-'4 4.171~10'~4.264~10-'~ 2.892~10'~ ZXC21 1259 2.25 72 0.014 0.075 4 . 0 8 4 ~ 1 0 - ' ~ 1 . 1 4 3 ~ 1 0 ' ~ 8 . 7 8 4 ~ 1 0 - " 2 . 8 4 6 ~ 1 0 " ZXG17 1295 2.42 78 0.011 0.086 4.303X10-l3 8.521X 10" 3 . 1 0 2 X 1 0 - ' ~ 9.241x1016 T, Temperature estimated using Bertrand and Mercier's geothermometer; P, pressure estimated using Kohler and ~ r e y ' s ' ~ ' (above solid line)[14' and (below solid line) geobarometers; 2 , depth inferred from equation: Z = 4 . 2 + 3 0 . 3 P , where P is pres- sure in GPa; oO. differential stress estimated from paleoblast grain size; 01, differential stress estimated from neoblast grain size; s o and 70, strain rate and equivalent viscosity estimated using oo stress value; i l and 71, strain rate and equivalent viscosity estimated using ol stress value. 2.2 Chemical compositions of minerals in xenoliths Microprobe analyses of chemical compositions of minerals from 18 spinel lherzolite and 20 garnet lherzolite samples have been carried out. Multi-points detection has been carried out within 174 SCIENCE IN CHINA (Series D) Vol. 41 a single grain in order to determine the homogeneity of the compositions of the mineral. The anal- ysis has shown that no composition zoning has occurred in these grains, and the data can be used to estimate the equilibrium temperature and pressure of the xenoliths studied. A special pro- gram'11 has been used in the detection of Ca content in olivine, in order to use the geobarometer of Kohler and Brey (1990) for pressure estimation of spinel Iherzolite. All analyses were carried out using a Cameca SX50 electron microprobe at Institute of Geology, Chinese Academy of Sciences. Several hundreds data have been obtained, but have not been listed in this because of the limit of space. 3 Estimation of rheological parameters of the upper mantle As has been noted above, mantle xenoliths in this region experienced a relatively complicated deformation history. In order to get better understanding of the deformation conditions and histo- ry, the relevant deformation parameters including differential stress, strain rate and viscosity should be determined. 3.1 Estimqtion of differential stress The differential stress during the deformation of xenoliths can be estimated by using mi- crostructural piezometers, such as free dislocation density, recrystallized grain size, subgrain size, spacing of dislocation walls. We used here recrystallized grain size and spacing of dislocation walls as piezometers . As was noted above, the xenoliths here exhibit predominantly the transition from protogranular to porphyroclastic texture. The grain size of olivine in these xenoliths shows a bi- modal distribution, representative of coarser porphyroclast (paleoblast) and smaller recrystallized grain (neoblast) . The measurement has shown that the two grain sizes are relatively homogeneous (with standard deviation of less than 20% ) . Ave Lallemant et al. [ I 7 ' have pointed out that the homogranular textures of paleoblast are representative of steady-state conditions in the upper man- tle, and the grain size yield stress compatible with large scale, steady state flow in the upper man- tle. The superimposed microstructures, including neoblasts, would appear to be related to later deformation process. We have measured the two kinds of grains separately, and used them to esti- mate the differential stress of two different stages of deformation. The paleopiezometer we used is proposed by Ross et al. [ l a ' . Moreover, the spacing of dislocation walls is also commonly regarded as a useful paleopiezometer, which yields stress representative of later stage of deformation, just like the neoblasts. We used here paleopiezometer proposed by ~ o r i u m i ' l ~ ' . The results show that the paleoblasts yield stress much lower than neoblasts and spacing of dislocation walls. The value is within a range of 6-16 MPa, and is relatively stable. As was not- ed by Ave Lallemant et al. , this relatively stable low stress might be representative of large-scale steady-state flow of the upper mantle. The neoblast and the spacing of dislocation walls yield much higher stress with greater variation. T h e neoblasts yield stress within the range of 30-100 MPa, while the spacings of dislocation walls yield stress value of 10-80 MPa for spinel lherzolite and 50-290 MPa for garnet lherzolite. We believe that the stress obtained from the two piezome- ters might represent the stress values of two different deformation events, or at least the different stages of one event. This conclusion, however, still cannot be confirmed, as significant differ- ences may arise when using different piezometers. It is commonly accepted that the recrystallized grain size of the various paleopiezometers is the most reliable. We will use and discuss here only No. 2 THERMAL STRUCTURE & RHEOLOGY O F UPPER MANTLE 175 the stress estimated by recrystallized grain size (table 1 ) . 3.2 Estimation of strain rate and equivalent viscosity Once the P, T and differential stress were determined, the strain rate can be calculated through the high temperature flow law of peridotites. We used the equation proposed by Cabanes and ~ r i ~ u e " ~ ] : E = 2 . 6 9 x 1 0 ~ ~ e- (63000 + 1 6 1 0 P ) / T ] a3.', x~[ where E is strain rate (in s - I ) , P is pressure in GPa, T is temperature in K, and a is differential stress in GPa. The equivalent viscosity can be calculated based on the equation 7 = a / 3 E . The re- sults of the calculation are listed in table 1 . In table 1 we used two different stress to calculate the strain rate and equivalent viscosity. They should represent the strain rate and viscosity of the large-scale steady state flow and the later deformation event, respectively. As has been noted above, no chemical composition zoning in the same grain has been found, and even the chemical compositions of paleoblasts are consistent with those of the neoblasts. It seems, therefore, that the two deformation events occurred under the same temperature condition, i. e. after the diapir when a new equilibration was reached. 4 Construction of upper mantle geotherm for Zhejiang Province and its geophysical implication 4.1 Upper mantle geotherm for Zhejiang Province The upper mantle geotherm for Zhejiang Province can be constructed on the basis of the P and T estimates of mantle xenoliths listed in table 1( fig. 1) . From table 1 and fig. 1, we can see that the constructed geotherm is within the range of 900- 1 295°C . The temperature range of spinel lherzolite is 900-1 130"C, while that of garnet lherzolite is 1 130-1 295°C . Fig. 1 also shows the transition curve from spinel lherzolite to garnet lherzolite according to 0' ~ e i l l ' ~ " .I t can be seen that almost all the data points of spinel lherzolite fall into the stable field of spinel lherzolite, except one point which falls just on the transition curve. All the data points of garnet lherzo- lite fall into the stable field of garnet lherzo- lite. All these indicate that the data used Fig. 1 . A xenolith-derived geotherm ( a ) and the structures ( b ) of here are reasonable and reliable. The upper the upper mantle of Zhejiang Province. The spinel lherzolite to garnet lherzolite transition is taken from the data of 0' ~ e i l l ' ~ ' ]The solid . geothem for eastern China 'On- line is the obtained geotherm for Zhejiang Province, while the dash structed by XU et al. ['I is also shown in line is the geotherm for eastern China proposed by Xu et al. ['I. The fig. 1 for ~h~ geotherm in the histogram in the figure can be used to infer crust-mantle boundary, where the blank column represents spinel lherzolite while the hatched present paper is slightly lower than that of column represents garnet Iherzolite. 0 , Data points of spinel Iherzo- xu et al. , and there is no inflection at Iite xenoliths; A , data points of garnet lherzolite xenoliths. CMB: crust-mantle boundary; the lowest dash line in fig. l ( b ) is believed to about 60 km depth. The first difference be the top of asthenosphere. 176 SCIENCE IN CHINA (Series D) Vol. 41 can easily be explained by the fact that the geotherm proposed by Xu et al. has taken eastern Chi- na as a whole. In fact, there are significant differences among different parts of eastern China. The second difference is possibly caused by the lack of data of Xu et al. at the transition from spinel lherzolite and garnet lherzolite, and the inflection based mainly on extrapolation. According to present geotherm no significant inflection has occurred. 4.2 Geophysical implication A detailed discussion was given by Xu et al. in their paper about the geophysical implications of the constructed geotherm for eastern China. As was noted above, the present geotherm is close to that of Xu et al., except the inflection in their geotherm. Obviously, the present geotherm is also higher than that of oceanic geotherm and is much higher than that of the Kaapval craton, but is similar to that for southeastern ~ u s t r a l i a ' ~ 'It is commonly accepted that this high thermal . state may be caused by the deep-seated magmatic process, mantle upwelling (crustal thinning) and increase of heat flow in the lithosphere. In Zhejiang Province, we believe that mantle up- welling (diapir) was the main cause for the high geotherm in this region. The crust-mantle boundary can roughly be inferred from the constructed geotherm. As the top of the upper mantle consists of spinel lherzolite, the smallest depth ( t h e lowest temperature) for spinel lherzolite must represent the crust-mantle boundary['321. From the histogram in fig. 1 we may infer that the crust-mantle boundary in this region is at about 34 km. This result is con- sistent basically with the recent results of geophysical prospecting[221, in which the crustal thick- ness for this region determined by gravity data is about 33. 2 km. Fig. 1 also shows that the boundary between spinel lherzolite and garnet lherzolite is at about 60 km depth (the correspond- ing temperature is about 1 130°C ), which is in good agreement with the result of Xu et al. ['I. It is suggested that within the depth range of 34-60 km, the upper mantle comprises mainly spinel lherzolite, while below 60 km it consists mainly of garnet lherzolite. I t is usually considered that the temperature of the asthenosphere should be higher than 1 200°C , at which T >O. 7 T,(melt- ing temperature of peridotite) and peridotite will be softened by plastic flow. If we take this tem- perature as the boundary between the lithosphere and the asthenosphere, then the top of astheno- sphere in this region is at about 75 km, and the main composition is still garnet lherzolite. This may indicate that asthenospheric diapir had occurred in this region before late Tertiary (mantle xenoliths were entrained by basaltic magma during late Tertiary). 5 Rheological features of the upper mantle beneath Zhejiang Province Based on the rheological parameters listed in table 1, a profile of rheological parameters ver- sus the depth can be constructed. As has been pointed out above, at least two deformation events can be recognized in the upper mantle of this region. The two events, therefore, should be con- sidered separately. Fig. 2 shows the results. ( a ) , ( b ) and ( c ) represent the earlier deformation process, while ( d ) , ( e ) and ( f ) represent the later event. Fig. 2 ( a ) shows that the differential stress for the earlier event for garnet lherzolite is slightly greater than that for spinel lherzolite. The stress was relatively low and stable, within the range of 5-15 MPa, decreasing with depth. Fig. 2 ( b ) and (c) show that the strain rate increases with depth, while the equivalent viscosity decreases with depth, showing a good linear correlation. Fig. 2 ( d ) , ( e ) and ( f ) show that during the later deformation process, the differential stress for garnet lherzolite shows a clear No. 2 THERMAL STRUCTURE & RHEOLOGY O F UPPER MANTLE 177 tendency to decrease with increasing depth, but this is less clear in spinel lherzolite xenoliths. The strain and viscosity profiles show slight inflection between garnet lherzolite and spinel lherzolite. It seems that there were some differences in the later deformation process between spinel lherzolite and garnet lherzolite. u, - u,/MPa -log t / s - ' log tl/Pa. s 01 - as/MPa -log i / s - ' log ?/Pa.s Fig. 2. The differential stress, strain rate and equivalent viscosity profiles for the upper mantle of Zhejiang Province. (a), (b) and ( c ) are for the early deformation stage; while ( d ) , (e) and (f) for the later deformation stage. The lithosphere-asthenosphere boundary can also be inferred from these figures. It is com- monly accepted, that the strain rate value for the asthenosphere is higher than 10-14s-1, while the viscosity is lower than 1 0 ~ ~ .~ For - the earlier deformation event, these values will com- s a pletely be obtained at 1 200"C, corresponding to a depth of about 75 km, which is in good agree- ment with the conclusion obtained from geotherm. When considering the high stress level for the late deformation process, however, we found that the temperature and depth at which the strain rate and viscosity reach the value for asthenosphere will be greatly decreased, i. e. at about 1050°C or 55 km depth (fig. 2 ( e ) , ( f ) ) . This may indicate that after the diapir of the upper mantle in this region, a high strain rate and low viscosity zone occurred within the range of 20 km above the top of the asthenosphere due to local high stress level. Obviously, this low viscosity zone differs from asthenosphere, so that it is reasonable to regard it as "anomalous mantle". In consideration of the significant variation of the differential stress even at the same depth, we be- lieve that this was a small scale and locally existed zone. Nicolas et al. [231 in their study on Massif Central volcanic region have refined the original hypothesis of one large-scale diapir and hhve sug- gested the existence of several smaller diapirs to explain this deformed mantle. Recently, ' ~ pointed out that it is simpler and more realistic to think of the lithospheric mantle ~ o w n e s has ~ ~ as containing numerous shear zones resulting from lithospheric thinning and rifting. Our result has shown that the mantle diapir in this region should be a small-scale one, while the low viscosity zone might be a series of shear zone as proposed by Downes. I n addition, recent geophysical study in this region also supported this conclusion. For example, the comprehensive geophysical prospecting in ~ u n x i - ~ e n z h o u [ ~ ~ ] revealed that a high conductivity layer (asthenosphere) area has 178 SCIENCE IN CHINA (Series D) Vol. 41 is pervasively observed in Zhejiang Province. It has an average buried depth of 100 km, decreas- ing from west to east, and the depth has become 65 km to the sea shore. Asthenospheric up- welling has been recognized in 4 low resistivity zones. Obviously, the 4 upwellings of astheno- sphere should correspond to the small-scale diapirs. References 1 Xu Yigang, Lin Chuanyong, Shi Lanbin et al. , Upper mantle geotherm for eastern China and its geological implications, Sci- ence in China ( i n Chinese), Ser. B, 1995, 38(4): 1482. 2 0' Reilly, S. Y. , Griffin, W. L . , A xenolith-derived geotherms for southeastern Australia and its geophysical implications, Tectonophys . , 1985, 111 : 41. 3 Jin Zhenmin, Green, 11. H. W . , Borch, R . S. et a l . , Mantle xenoliths and geothermal indications of modern back-arc in eastern China, Science in China (in Chinese), Ser. B, 1993, 23: 410. 4 Bureau of Geology and Mineral Resources of Zhejiang Province, Regional Geology of Zhejiang Province, Beijing: Geological Publishing House, 1989, 688. 5 Liu Ruoxin, Geochronology and Geochemistry of Genozoic Volcanic Rocks in China (in Chinese), &jing: Seismological Press, 1992, 1-43. 6 Cong Bolin, Zhang Ruyuan, Petrogenesis of nepheline basalts and their ultramafic inclusions from Xilong, Zhejiang Province, Petrological Research (in Chinese), No. 3, Beijing: Geological Publishing House, 1983, 95-110. 7 Liu Ruoxin, The features and Dynamics of the Upper Mantle of China ( in Chinese), Beijing : Seismological Press, 1990, 23-24. 8 Lin Chuanyong, Shi Lanbin, Chen Xiaode et al., Rheological features of garnet lherzolite xenoliths ffrom Xinchang, Zhejiang Province, China and their geological implications, Acta Petrologica Sinica (in Chinese), 1995, l l ( 1 ) : 55. 9 in Brey, G . P . , Kohler, T . , Geotherm~barometr~ four-phase lherwlites 11. New thermobarometer and practical assessment of existing thermobarometers, Jour. Petrol. , 1990, 31 : 1353. Xu Yigang, Geothermometer applicable to mantle xenoliths, Acta Petrologica Sinica (in Chinese), 1993, 9(2) : 167. Bertrand, P . , Mercier, J . - C C . , The mutual solubility of coexisting ortho- and clinopyroxene: toward an absolute geother- mometer for the natural system? Earth Planet. Sci. L e t t . , 1985, 77: 109. Nickel, K. G . , Brey, G. P . , Kogarko, L . , Orthopyroxene clinopyroxene equilibria in the system Ca0-MgO-AI20,-Si0, (CMAS) : New experimental results and implications for two pyroxenes thermometry, G n t r i b . Mineral. Petrol. , 1985, 91: 44. Wwd, B. J . , Solubility of alumina in orthopyroxene coexisting with garnet, Contrib . Mineral. Petrol., 1974, 45: 1. Nickel, K . G . , Green, D. H . , Empirical geothermobarometry for garnet peridotite and implications for the nature of the lithosphere, kimberlites and diamond, Earth Planet. Sci . Lett. , 1985, 73: 158. Mercier, J . -C. , Single pyroxene thermobarometry, Tectonophys . , 1980, 70 : 1. C. Kohler, T . , Brey, G. P. , Calcium exchange between olivine and clinopyroxene calibrated as geothermo-barometer for natural peridotite from 2-60kb with applications, Geochem. Cosmochem. Acta, 1990, 54: 2375. Ave Lallement, H. G. , Mercier, J . -C. C. , Carter, N. L. , et al. , Rheology of the upper mantle: inferences from peridotite xenoliths, Tectonophys . , 1980, 70: 85. Ross, J . V . , Ave Lallemant, H. G . , Carter, N. L. , Stress dependence of recrystallized grain and subgrain size in olivine, Tectonophysics, 1980, 70 : 39. Toriumi, M. , Relation betwen dislocation density and sub-grain size of naturally deformed olivine in peridotites, Contrib. Mineral. Petrol., 1979, 68: 181. Cabanes, N . , Brique, L . , Hydration of an active shear zone: interaction between deformation, metasomatism and magma- tism, Earth Planet. Sci. L e t t . , 1987, 81: 233. O'Neill, H. St. C., The transition between spinel lherwlite and garnet lherzolite, and its use as geobarometer, Contrib. Mineral. Petrol., 1981, 77: 185. Compiling Group of "The results of deep-seated geophysical prospecting", State Seismological Bureau, The Result of Geo- physic Prospecting of the Crust and Upper Mantle of China (in Chinese), Beijing: Seismological Press, 1986, 350-352. Nicolas, A . , Lucazeau, F . , Bayer, R. , Peridotite xenoliths in Massif Central Basalts, France: textural and geophysical evi- dence for asthenospheric diapirsm, Mantle Xenoliths, New York: John Willey & Sons, 1987, 563-574. Downes, H. , Shear zones in the upper mantle-relation between geochemical enrichment and deformation in mantle peridotites, Geology, 1990, 18: 374. Li Jiliang, The Structures and Geologic Evolution of the Southeast Continent of China, Beijing: Publishing House of Metal- lurgical Industry, 1993, 233-256.
Pages to are hidden for
"Thermal structure and rheology of upper mantle beneath Zhejiang"Please download to view full document