冀东地区变质岩中斜方辉石的研究   总被引：2，自引：0，他引：2  

李殿超 《岩石矿物学杂志》1995,14(2):185-190

通过对冀东地区３４个斜方辉石榈的研究得出结论：斜方辉石由早、晚两期变质作用形成。斜方辉石的化学成分变化主要与变质作用的条件及岩中共存矿物种类有关，同时也受原岩成分的控制。据温压计的估算结果，早期变质作用的温度为８１７－９３７℃、压力为０．９９－１．１１ＧＰａ；晚期变质作用的温度为７４７－８３４℃、压力为０．９５ＧＰａ。  相似文献   

大别山区深部地壳的变质岩石学证迹：罗田惠兰山一带的麻粒岩研究   总被引：20，自引：3，他引：20  

游振东  陈能松 《岩石学报》1995,11(2):137-147

大别杂岩中新太古代或古元古代麻粒岩相岩石分布具一定的区域规模。罗田黄土岭、惠兰山一带出露中性和基性麻粒岩，其矿物组合分别为；１．Ｇｒｔ＋Ｏｐｘ１＋Ｂｉ＋Ｋｆｓ＋Ｐｌ（Ａｎ２０）（中性），２．Ｇｒｔ＋Ｈｂ１＋Ｏｐｘ＋Ｃｐｘ＋Ｐｌ（Ａｎ４Ｏ）＋Ｉｌｍ（基性），它们的高峰变质条件分别为ＰＯ．８９～１．０４Ｇｐａ、Ｔ７５０～８５０℃（中性）以及Ｐ０．９～１．２９ＧＰａ、Ｔ６８２～８８０℃，平均７７１±５３℃（基性），说明其形成深度在３０ｋｍ以上。在中性麻粒岩中发现堇青石＋石英和堇青石＋黑云母的后成合晶，分别位于Ｇｒｔ与Ｏｐｘ１之间或穿插于Ｇｒｔ晶内，退变质反应条件为Ｐ为０．４１～０．５５ＧＰａ，Ｔ＝７１０℃，属减压退变质性质；后成合晶的形态与区域面理无关，说明减压退变质反映了碰撞造山带后期的近绝热隆升。区域花岗岩或地幔热流可能是绝热隆升的热源，现今出露的深源麻粒岩有过长期居留下地壳的历史，它们的抬升剥露是后期构造事件所致。  相似文献   

Chloritoid-bearing rocks associated with blueschists and eclogites, northern New Caledonia   总被引：4，自引：0，他引：4  

EDWARD D. GHENT  MAVIS Z. STOUT  P. M. BLACK  R. N. BROTHERS 《Journal of Metamorphic Geology》1987,5(2):239-254

Abstract Chloritoid-bearing metasedimentary rocks occur in close proximity to blueschists and eclogites in the Tertiary high-pressure metamorphic belt of northern New Caledonia. The typical assemblage of chloritoid-bearing rocks in the epidote zone is quartzchlorite-muscovite-garnet-chloritoid. In the omphacite zone, epidote is an additional member of the chloritoid-bearing assemblage. Paragonite is rare, plagioclase was not detected, and rutile and ilmenite are the Fe-Ti oxide phases. Chloritoid-glaucophane is not a common assemblage. Chloritoid-bearing rocks have relatively low (Ca+K+Na)/Al ratios and the chloritoids are relatively Mg-rich with Mg/ (Mg+Fe) up to about 0.4. A comparison of the mineral assemblages and mineral chemistry with experimental and computed phase equilibria suggest an upper temperature limit near 560° C in the omphacite zone and a minimum temperature limit near 450° C at 10 kbar. An empirical garnet-chlorite Fe-Mg exchange thermometer does not yield consistent results for the higher-grade rocks, suggesting T s ranging from 390 to 535° C in the omphacite zone and 420–465° C in the epidote zone. The distribution coefficient K _D = (Fe/Mg)_ctd/(Fe/Mg)_chl for chloritoid and chlorite ranges from 3.9 to 6.4, values which are lower than those (=10) from lower greenschist facies rocks, but are near those of upper greenschist facies and albite-epidote amphibolite facies.  相似文献   

华北克拉通太古宙上壳岩早前寒武纪构造变形与变质作用关系——以北京密云沙厂地区为例     

Yang Zhensheng Liu Wuxu 《吉林大学学报(地球科学版)》1986,(4)

沙厂铁矿区上壳岩在太古宙时期经历了麻粒岩相、角闪岩相和绿片岩相的多相变质作用,这种多相变质作用的发生及其分布特点是与本区台怀运动旋回的两幕构造变形的形成有密切关系。本文根据不同变质相的矿物组合与不同变形幕构造片理的相互关系的研究得出角闪岩相退变是与台怀变形序列的第一幕变形相对应,而绿片岩相退变是与第二幕变形有联系的结论。退变质作用的不均匀性,即其强弱的表现与不同变形幕的构造变形有直接关系。  相似文献   

晋北恒山地区变质作用特征及其演化   总被引：1，自引：0，他引：1  

Xu Xuechun 《吉林大学学报(地球科学版)》1986,(4)

本文根据施莱纳玛克斯分析方法,编制岩石成因网系图,讨论本区两套变质岩系的变质作用特征和演化。矿物共生组合和矿物对地温地压计的研究表明,恒山群和繁峙群分别为两期变质作用的产物,其变质程度分别为麻粒岩相和角闪岩相。本区变质作用随时间的演化而减弱,与地壳演化的总趋势是一致的。  相似文献   

Chloritoid and staurolite stability: implications for metamorphism in the Archaean Yilgarn Block, Western Australia   总被引：2，自引：0，他引：2  

M. J. BICKLE  N. J. ARCHIBALD 《Journal of Metamorphic Geology》1984,2(3):179-203

Abstract The stability of quartz-chloritoid-staurolite-almandine-cordierite and aluminium silicates is used to constrain both metamorphic conditions and pressure-temperature trajectories for two localities within the 2700 Ma Archaean Yilgarn Block in Western Australia. Available experimental data are used to calculate thermodynamic data for a self-consistent set of equilibria between these minerals. A lower amphibolite facies locality from the margin of a lower strain area contains assemblages including quartz-chloritoid-staurolite-garnet-biotite with altered cordierite replacing chloritoid, quartz-staurolite-andalusite, and quartz-cordierite-andalusite-biotite. This locality was heated to 530–560°C in the andalusite field, at 4.2 kbar. A sample from a mid- to upper-amphibolite facies, highly strained locality contains relict staurolite enclosed by andalusite, in turn replaced by cordierite and muscovite with biotite and sillimanite in the matrix. The assemblage was heated isobarically from conditions near the maximum experienced by the lower grade locality of 560°C at 4.2 kbar to temperatures in excess of the andalusite-sillimanite transition but within the quartz plus muscovite stability field (600–650°C). The higher grade locality is close to a granitoid dome and sections based on gravity profiles reveal that this locality is underlain by granitoid at shallow depths. The higher grade metamorphism apparently reflects superposition of the thermal aureole on regional metamorphic conditions similar to those in the lower grade areas.  相似文献   

粤西云炉紫苏花岗岩及其麻粒岩包体的主要特点和成因讨论   总被引：20，自引：7，他引：20  

陈斌  庄育勋 《岩石学报》1994,10(2):139-150

云炉含有麻粒岩包体的紫苏花岗岩出露于粤西云开大山加里东造山带。这种紫苏花岗岩是麻粒岩在水不饱和的条件下发生深熔作用的结果．结晶温度在８００℃以上，氧逸度（ｆｏ２）和水逸度（ｆＨ２Ｏ）分别为１．０１３×１０８．６Ｐａ和４５．４ＭＰａ，定位深度约１７ｋｍ，单颗粒锆石Ｕ－Ｐｈ同位素年龄为４５０±１０Ｍａ。岩体中的麻粒岩包体来自紫苏花岗岩源区．反映源区的变质条件为Ｐ＝０．６～０．６９ＧＰ８，Ｔ＝８０７～８３６°ａＨ２ｏ＝０．２７。  相似文献   

A corundum and sapphirine paragenesis from the Limpopo Mobile Belt, southern Africa   总被引：3，自引：0，他引：3  

PETER C. HORROCKS 《Journal of Metamorphic Geology》1983,1(1):13-23

An assemblage consisting of corundum, sapphirine, spinel, cordierite, garnet, biotite and bronzite is described from the Messina area of the Limpopo Mobile Belt, and consideration given to its petrogenesis. Various geothermometers and geobarometers have been applied in an attempt to determine the temperatures and pressures of metamorphism.
A former coexistence of garnet and corundum is suggested to have developed during the earliest high pressure phase of the metamorphism, where temperatures exceeded 800°C and pressures as high as 10kbar may have been experienced. Subsequently, continuous retrograding reactions from medium pressure granulite facies at about 800°C and 8kbar towards amphibolite facies generated spinel, cordierite, sapphirine and possibly also bronzite. The most notable reaction was probably of the form: garnet + corundum = cordierite + sapphirine + spinel.  相似文献   

The role of the fluid phase during regional metamorphism and deformation   总被引：8，自引：0，他引：8  

M. A. ETHERIDGE  V. J. WALL  R. H. VERNON 《Journal of Metamorphic Geology》1983,1(3):205-226

Evidence from rock microstructures, mass transfer and isotopic exchange indicates that substantial quantities of aqueous fluids are involved in low- and medium-grade regional metamorphism. Similar conclusions are drawn from many retrograde environments, whereas high-grade metamorphic fluids may be melt dominated. The mobile fluids play essential roles in metamorphic reactions, mass transport and deformation processes. These processes are linked by the mechanical consequences of metamorphic fluid pressures (P_f) generally being greater than or equal to the minimum principal compressive stress. Under such conditions metamorphic porosity comprises grain boundary tubules and bubbles together with continuously generated (and healed) microfractures. Deformation results in significant interconnected porosity and hence enhanced permeability. Lithologically and structurally controlled permeability variations may cause effective fluid channelling.
Simple Rayleigh-Darcy modelling of a uniformly permeable, crustal slab shows that convective instability of metamorphic fluid is expected at the permeabilities suggested for the high P_f metamorphic conditions. Complex, large-scale convective cells operating in overpressured, but capped systems may provide a satisfactory explanation for the large fluid/rock ratios and extensive mass transport demonstrated for many low- and medium-grade metamorphic environments. Such large-scale fluid circulation may have important consequences for heat transfer in and the thermal evolution of metamorphic belts.  相似文献   

Evolution of the REE mineralogy in HP–LT metapelites of the Sebtide complex, Rif, Morocco: Monazite stability and geochronology     

Emilie Janots  Franois Negro  Fabrice Brunet  Bruno Goff  Martin Engi  Mohamed L. Bouybaoune 《Lithos》2006,87(3-4):214-234

REE mineralogy was characterized at the micrometer scale (using scanning electron microscopy) in the four tectono-metamorphic units of the Beni Mzala window, Sebtide Complex, Internal Rif, Morocco, which sample a HP-LT metamorphic gradient from subgreenschist to blueschist/eclogite facies. These tectonic units are composed of garnet-free metapelites (and associated synmetamorphic veins) from the same homogeneous aluminium-rich and calcium-poor protolith. In that context, mineralogical differences between units are assumed to result from contrasted pressure and temperature histories. Light REE-bearing Al-phosphates of the crandallite group with florencite-rich composition and variable goyazite content are the dominant LREE minerals in the lowest-grade units, Tizgarine (300 °C, 3 kbar as peak conditions) and Boquete de Anjera (350 °C, 10 kbar). In the latter unit, metamorphic florencite is associated with MREE-rich monazite. In the schist of the highest-grade units, Beni Mzala 2 (420–450 °C, 12 kbar) and Beni Mzala 1 (550 °C, 16 kbar), associations of allanite-rich epidote and synchisite (a LREE-fluorocarbonate) are found whereas florencite and monazite are no longer observed. At the wall of the quartz–kyanite veins, retrograde monazite-(Ce) with grain size of 20 to 50 μm is the only LREE-bearing mineral. Th–Pb and U–Pb SIMS data on some of these grains yield ages of 21.3 ± 1.7 Ma and 20.9 ± 2.1 Ma, respectively, consistent with previous K–Ar ages obtained on retrograde clay–mica mixtures in rocks from the same locality. The identification of a stability field for monazite in high-pressure aluminous metapelites with an upper thermal-limit below 450 °C as well as the derivation of meaningful U–Pb and Th–Pb SIMS ages demonstrates the monazite potential for dating HP-LT metapelites. However, since, under these conditions, monazite growth occurs below its admitted closure-temperature, these ages must be interpreted on the basis of monazite textural relationships.  相似文献