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1.
Mineral and fluid inclusions in zircon of UHP metamorphic rocks from the CCSD-main drill hole: A record of metamorphism and fluid activity 总被引：18，自引：0，他引：18
The Chinese Continental Scientific Drilling (CCSD) main drill hole (0–3000 m) in Donghai, southern Sulu orogen, consists of eclogite, paragneiss, orthogneiss, schist and garnet peridotite. Detailed investigations of Raman, cathodoluminescence, and microprobe analyses show that zircons from most eclogites, gneisses and schists have oscillatory zoned magmatic cores with low-pressure mineral inclusions of Qtz, Pl, Kf and Ap, and a metamorphic rim with relatively uniform luminescence and eclogite-facies mineral inclusions of Grt, Omp, Phn, Coe and Rt. The chemical compositions of the UHP metamorphic mineral inclusions in zircon are similar to those from the matrix of the host rocks. Similar UHP metamorphic P–T conditions of about 770 °C and 32 kbar were estimated from coexisting minerals in zircon and in the matrix. These observations suggest that all investigated lithologies experienced a joint in situ UHP metamorphism during continental deep subduction. In rare cases, magmatic cores of zircon contain coesite and omphacite inclusions and show patchy and irregular luminescence, implying that the cores have been largely altered possibly by fluid–mineral interaction during UHP metamorphism.
Abundant H2O–CO2, H2O- or CO2-dominated fluid inclusions with low to medium salinities occur isolated or clustered in the magmatic cores of some zircons, coexisting with low-P mineral inclusions. These fluid inclusions should have been trapped during magmatic crystallization and thus as primary. Only few H2O- and/or CO2-dominated fluid inclusions were found to occur together with UHP mineral inclusions in zircons of metamorphic origin, indicating that UHP metamorphism occurred under relatively dry conditions. The diversity in fluid inclusion populations in UHP rocks from different depths suggests a closed fluid system, without large-scale fluid migration during subduction and exhumation. 相似文献
2.
柴北缘夹榴辉岩的片麻岩（片岩）地球化学、Sm-Nd和U-Pb同位素研究——深俯冲的前寒武纪变质基底？ 总被引：18，自引：1，他引：18
在柴北缘的鱼卡-锡铁山-沙柳河一带,出露夹有榴辉岩透镜体的花岗质片麻岩(正片麻岩)和副片麻岩(片岩)。地球化学和Sm-Nd同位素数据显示副片麻岩(片岩)与正片麻岩具有类似的地球化学成分和一致的Nd模式年龄(1.88～2.18Ga),结合副片麻岩(片岩)局部包在正片麻岩中的野外关系,正片麻岩可能为副片麻岩(片岩)原地熔融作用的产物。U-Pb锆石测定表明熔融作用产生的正片麻岩的岩浆形成时代为952Ma。另外,这些夹榴辉岩的片麻岩(片岩)也与柴北缘北侧不夹榴辉岩的深变质基底片麻岩和中南祁连地块的变质基底片麻岩有相似Sm-Nd同位素特征和近一致Nd模式年龄(1.87～2.26Ga)。表明它们具有明显的亲缘关系,可能来源于具有古元古代晚期地壳形成年龄的同一变质基底。然而,与柴北缘北 侧和祁连地块的深变质基底岩石不同的是,这套含榴辉岩的片麻岩(片岩)明显遭受了早古生代变质作用的影响,正片麻岩锆石U-Pb测定获得的下交点年龄为478±44Ma,与柴北缘地区榴辉岩的变质锆石的年龄在误差范围内一致;而已在都兰地区副片麻岩锆石中柯石英包体的发现也证明了含榴辉岩的片麻岩(片岩)与榴辉岩一样同样经历了UHP变质作用。因此,我们认为柴北缘含榴辉岩的片麻岩虽然具有与相邻变质基底相似的早期演化历史,但在早古生代又与所夹的榴辉岩 相似文献
3.
本文通过某些矿物之间的转化及成分的变化，研究变质反应的状态。将区内麻粒岩相变质作用划分为四个阶段，并依据变质作用演化过程中的温度、压力的变化推定了ＰＴ＿ｔ轨迹。 相似文献
4.
矿物之间的元素和同位素平衡:地质测温和等时线定年的热力学和动力学控制 总被引：1，自引：0，他引：1
在特定的地质事件过程中,矿物等时线放射体系是否达到并且保持了平衡是变质岩Sm-Nd和Rb-Sr同位素年代学中的一个重要问题。在这个问题上矿物对O同位素测温与矿物等时线定年相似,因此两者之间可以相互制约。在岩浆岩和变质岩中,矿物中Sm-Nd、Sr和O之间的扩散速率在无水的条件下一般具有可比性,因此矿物之间O同位素的平衡状态可以用来对Sm-Nd和Rb-Sr定年的有效性进行检验。对大别-苏鲁造山带超高压变质岩的Sm-Nd和Rb-Sr等时线矿物进行O同位素测温,得到Sm-Nd等时线有时给出三叠纪年龄,有时给出非三叠纪年龄;对应的矿物O同位素分馏分别处于平衡和不平衡状态。对于引起非三叠纪等时线年龄的原因,一方面可以是由于榴辉岩相变质过程中同位素体系没有达到平衡,另一方面则可能角闪岩相退变质作用打破了平衡。等时线矿物中初始同位素比值的均一化速率主要受慢扩散矿物的影响,而矿物等时线时钟的启动主要受高母/子比值矿物控制。因此在变质作用过程中,只有当高母/子比值矿物同时具有快的放射成因同位素扩散速率,才可能得到有效的矿物等时线来用于变质年龄的测定。根据不同矿物中不同元素在扩散速率上的差异,能够定量估计大陆碰撞过程中榴辉岩相变质的持续时间。应用增量方法和离子孔隙度经验模型,不仅分别能够从理论上准确计算所有固体矿物的氧同位素分馏系数和获得不同矿物中元素的扩散参数,而且分别能够定量预测热力学平衡条件下共生矿物之间的18O富集顺序和相同条件下矿物中元素扩散速率的相对快慢。 相似文献
5.
浙西南遂昌-大柘地区八都岩群在印支期变质事件影响下发生变质变形,通过详细野外调查和岩相学研究,可将其划分为3期变质变形序列：S1变形期,NW向片麻理记录的残留紧闭褶皱,共生矿物组合为石榴子石变斑晶及其内部定向分布的包裹体矿物,石榴子石+黑云母+石英（泥质）和石榴子石+角闪石+斜长石+石英（长英质）;S2变形期,区域性宽缓褶皱及NE向缓倾透入性片麻理,共生矿物组合为石榴子石变斑晶及定向分布的基质矿物,矽线石+石榴子石+黑云母+石英+斜长石±钾长石（泥质）和石榴子石+钾长石+斜长石+黑云母+石英（长英质）;S3变形期,NE向陡倾透入性片麻理及韧脆性断裂大部分被花岗斑岩脉填充,共生矿物组合为石榴子石变斑晶及其周围退变矿物,石榴子石+矽线石+堇青石+斜长石+黑云母+石英±钾长石（泥质）和角闪石+斜长石+黑云母+钛铁矿（长英质）。结合前人研究成果,八都岩群印支期变质事件峰期变质程度达到麻粒岩相,显示顺时针近等温降压（ITD）型的p-T演化轨迹,S1-S3变质变形反映出从俯冲碰撞到快速折返冷却的演化过程,伴随S3同期侵位的花岗斑岩锆石U-Pb定年结果,将该演化过程完成时间约束在229.7 Ma,可能是浙西南地区对印支期古特提斯洋域内印支-华南-华北板块之间俯冲-碰撞过程的响应。 相似文献
6.
Multiple zircon growth during fast exhumation of diamondiferous, deeply subducted continental crust (Kokchetav Massif, Kazakhstan) 总被引：36，自引：0，他引：36
Jörg Hermann Daniela Rubatto Andrei Korsakov Vladislav S. Shatsky 《Contributions to Mineralogy and Petrology》2001,141(1):66-82
Diamondiferous rocks from the Kokchetav Massif, Kazakhstan, represent deeply subducted continental crust. In order to constrain the age of ultra high pressure (UHP) metamorphism and subsequent retrogression during exhumation, zircons from diamondiferous gneisses and metacarbonates have been investigated by a combined petrological and isotopic study. Four different zircon domains were distinguished on the basis of transmitted light microscopy, cathodoluminescence, trace element contents and mineral inclusions. Mineral inclusions and trace element characteristics of the zircon domains permit us to relate zircon growth to metamorphic conditions. Domain 1 consists of rounded cores and lacks evidence of UHP metamorphism. Domain 2 contains diamond, coesite, omphacite and titanian phengite inclusions providing evidence that it formed at UHP metamorphic conditions (P>43 kbar; T~950 °C). Domain 3 is characterised by low-pressure mineral inclusions such as garnet, biotite and plagioclase, which are common minerals in the granulite-facies overprint of the gneisses (P~10 kbar; T~800 °C). This multi-stage zircon growth during cooling and exhumation of the diamondiferous rocks can be best explained by zircon growth from Zr-saturated partial melts present in the gneisses. Domain 4 forms idiomorphic overgrowths and the rare earth element pattern indicates that it formed without coexisting garnet, most probably at amphibolite-facies conditions (P~5 kbar; T~600 °C). The metamorphic zircon domains were dated by SHRIMP ion microprobe and yielded ages of 527LJ, 528NJ and 526LJ Ma for domains 2, 3 and 4 respectively. These indistinguishable ages provide evidence for a fast exhumation beyond the resolution of SHRIMP dating. The mean age of all zircons formed between UHP metamorphic conditions and granulite-facies metamorphism is 528Dž Ma, indicating that decompression took place in less than 6 Ma. Hence, the deeply subducted continental crust was exhumed from mantle depth to the base of the crust at rates higher than 1.8 cm/year. We propose a two-stage exhumation model to explain the obtained P-T-t path. Fast exhumation on top of the subducted slab from depth >140 to ~35 km was driven by buoyancy and facilitated by the presence of partial melts. A period of near isobaric cooling was followed by a second decompression event probably related to extension in a late stage of continental collision. 相似文献
7.
Identification of the scales of differential element mobility in a ductile fault zone 总被引：3，自引：0，他引：3
Two fundamentally different scales of element mobility have been identified in the upper-amphibolite-facies Hunts Brook fault zone of south-central Connecticut, USA. Field relations, mineral chemistry, and 80 bulk rock analyses provide overwhelming evidence that the blastomylonitic schists and gneisses of the fault zone were derived from the enclosing granodioritic Rope Ferry orthogneiss. Two-sample mass balance calculations between the Rope Ferry Gneiss and fault rocks strongly suggest that the Rope Ferry Gneiss was segregated into biotite-rich schists and quartz–plagioclase-rich gneisses through the centimetre-scale transfer of Si, Al, Ca, Na, Ba, and Zr from schists to gneisses. Three- and four-sample mass balance calculations provide convincing evidence that Al, Ca, Na, and Ba were lost and Si and K gained by the entire fault zone. Both scales of metasomatism have been identified at two localities separated by 20 km, implying that the metasomatic processes were pervasive throughout the fault zone.
From the mass balance calculations, an apparent disparity in K mobility arises. K appears to be gained by the entire fault zone, but is immobile during the centimetre-scale segregation. This is because mass balance calculations can only detect differential element mobility. Differential element mobility requires that the mechanism of metasomatism produces chemical potential gradients. Therefore, the identification of differentially mobile elements provides insight into the mechanisms of metasomatism. The immobility of K during segregation of schists and gneisses implies that the segregation was not achieved through the extraction of partial melt. However, the element mobility is reconcilable with deformation-driven metamorphic differentiation. The gains of Si and K and losses of Ca, Na, Al, and Ba for the entire fault zone are also inconsistent with the intrusion or extraction of partial melt, but may reflect the infiltration of a metasomatizing aqueous fluid. 相似文献
From the mass balance calculations, an apparent disparity in K mobility arises. K appears to be gained by the entire fault zone, but is immobile during the centimetre-scale segregation. This is because mass balance calculations can only detect differential element mobility. Differential element mobility requires that the mechanism of metasomatism produces chemical potential gradients. Therefore, the identification of differentially mobile elements provides insight into the mechanisms of metasomatism. The immobility of K during segregation of schists and gneisses implies that the segregation was not achieved through the extraction of partial melt. However, the element mobility is reconcilable with deformation-driven metamorphic differentiation. The gains of Si and K and losses of Ca, Na, Al, and Ba for the entire fault zone are also inconsistent with the intrusion or extraction of partial melt, but may reflect the infiltration of a metasomatizing aqueous fluid. 相似文献
8.
冀北水泉沟偏碱性杂岩体中石榴石的特征及其地质意义 总被引：3，自引：0，他引：3
石榴石是冀北水泉沟偏碱性岩体的二长岩类和正长岩类中常见的矿物之一，通过对其产出特征和矿物成分的分析研究，认为石榴石是央浆与大岩岩和片麻岩等围岩反应形成的矽卡岩矿物，从而说明岩浆演化过程曾经历上地壳的同化混染作用，同时也说明成矿过程经历了从矽卡岩阶段→中低温热液阶段，而非单一的中低温热液金矿成矿模式。 相似文献
9.
A newly identified skarn occurrence is described from the Neoproterozoic rocks of the SW Arabian shield. It is exposed to the SE, E and NE of the Al-Madhiq town. The skarn attributes correspond to those typical of the calcic skarns that host W-deposits. It is characterized as an exoskarn of the proximal type, related to a granitoid contact close to an impure quartzite bed within the regional metamorphic rocks of mixed sedimentary and volcanic derivation. The skarn is localized along a shear zone parallel to the regional faults and other major shear zones. Samples from the studied area contain characteristic skarn minerals that include both the prograde (brownish red grossular, ferrosalite, aluminian titanite-grothite, albite-oligoclase, scapolite), and retrograde (epidote, quartz, hornblende, calcite) assemblages. The pyroxenes are ferrosalites, Mn-bearing, and more like those from “oxidized” skarns; although garnets indicate it to be a “reduced” type skarn. Epidote mimicks that from typical skarns, as it bears a pistacite content of 15.9–20.7%. Grossular composition reflects a largely reduced genetic environment; as it is in solid solution with 6.5–21.6% andradite, 0–0.15% uvarovite, 0–0.47% pyrope, 4.33–18.75% almandine, and 0.4–8.58% spessartine molecules. Titanite composition varies from aluminian titanite to grothite, that may be analogous to the newly described Al-rich titanite from the low-pressure calc-silicate rocks. 相似文献
10.
七里坪硼矿床的主要矿石类型从岩石学角度看是方解石岩 ,它们由硼矿物和方解石组成 ,二者都是含硼气液交代白云石大理岩 (围岩 )的结果。矿石的化学成分既富钙又富镁 ,钙来自方解石 ,镁来自硼矿物 ,贫其它成分 ,因此夕卡岩型硼矿床不是传统的镁夕卡岩矿床 ,而是钙镁质夕卡岩矿床。 相似文献
11.
榍石在各类岩石中普遍存在，其稳定性受全岩成分、氧逸度和水活度以及温度和压力等因素影响。它在岩浆岩中主要存在于高Ca/Al比值的岩石中，在变质岩中常见于绿片岩相、蓝片岩相和角闪岩相岩石，在钙质变质岩中其稳定范围可达榴辉岩相或高压麻粒岩相。一般榍石结构中U含量较高，且具有高达高角闪岩相上限的U Pb同位素体系封闭温度，是理想的U-Pb定年矿物。由于榍石的组成元素均为岩石中的主要元素，很容易与其它矿物、熔体及流体发生反应，所以榍石的U-Pb年龄记录的更可能是结晶年龄，而不是简单的扩散重置年龄；也因为它容易反应，变质榍石复杂的U Pb体系可能记录了岩石的整个变质历史信息。通过与榍石平衡共生的矿物组合或利用榍石Zr温压计可确定岩石的P T条件，结合相关的榍石年龄信息即可建立变质过程的P T t轨迹。利用SHRIMP、LA MC ICP MS以及LA ICP MS方法可对不均一榍石颗粒内部进行原位微区分析得到有意义的U Pb年龄；利用榍石中Zr含量对温度，尤其是对压力比较敏感，可建立榍石Zr含量温压计。 相似文献
12.
扫描电镜能谱法测定独居石中铈、镧、钍等元素的含量 总被引：1，自引：0，他引：1
粒度细小的独居石、锆石等矿物在变质岩中含量少,利用岩石薄片偏反光显微镜鉴定技术一般不易确认,X射线粉晶衍射分析通常也检测不出此类微量矿物.利用电镜能谱分析技术能够检测出矿物主要组成元素,并能给出所测元素的浓度值.运用Casino程序和Quanta程序,据元素的浓度值可以计算出矿物中各元素的质量分数（%）.本次研究利用扫描电镜能谱仪检测了6个样品中微量矿物,结果表明：6个样品中主要元素组成为O、Ce、Nd、La、Al、P、Ca、Si、Ag、Th,与独居石矿物化学组成一致,可以判定所检测的6个样品为独居石. 相似文献
13.
The genesis and composition of lazurite was considered in the metasomatic rocks and deposits of the Baikal area, Pamirs, Hindu
Kush, and other regions. It was shown that formation of lazurite is related to the prograde bimetasomatic or contact-metasomatic
magnesian skarn processes developing in dolomites. The skarnized sedimentary or metamorphic rocks should be salt-bearing,
contain sulfur-bearing minerals, and be affected by Cl-bearing hydrothermal solutions. Both abyssal and hypabyssal skarn bodies
show distinct zoning. Depending on the PT parameters, their metasomatic columns can vary, with the preservation of the Mg/Ca ratio from the carbonate precursor. The
formation of contact-metasomatic lazurite mineralization is promoted by high-alkali magmatic solutions, which cause the replacement
of dolomites by skarn. Lazurite can also be formed during the postmagmatic stage, owing to a change in the mineral composition
of the adjacent aluminosilicate and magnesian-skarn rocks at abyssal and hypabyssal deposits around the world. The occurrence
of authigenic lazurite emphasizes its polygenetic formation.
Original Russian Text ? S.M. Aleksandrov, V.G. Senin, 2006, published in Geokhimiya, 2006, No. 10, pp. 1053–1067. 相似文献
14.
LIU Fulai SHEN Qihan Institute of Geology Chinese Academy of Geological Sciences Beijing 《《地质学报》英文版》2003,77(1):28-35
The early Precambrian khondalite series is widely distributed in the Jining-Zhuozi-Fengzhen-Liangcheng area, southeastern Inner Mongolia. The khondalite series mainly consists of sillimanite garnet potash feldspar (or two-feldspar) gneiss and garnet biotite plagioclase gneiss. These gneissic rocks have commonly experienced granulite-facies metamorphism. In zircons separated from sillimanite garnet potash feldspar gneisses, many mineral inclusions, including Sil, Grt, Ky, Kfs, Qtz and Ap, have been identified by the Laser Raman spectroscopy. Generally, prograde metamorphic mineral inclusion assemblages such as Ky + Kfs + Qtz + Ap and Ky + Grt + Kfs + Qtz are preserved in the core of zircon, while peak granulite-facies metamorphic minerals including Sil + Grt + Kfs + Qtz and Sil + Grt + Kfs + Qtz + Ap are identified in the mantle and rim of the same zircon. However, in some zircons are only preserved the peak metamorphic minerals such as Sil + Grt + Kfs + Qtz and Sil + Grt + Kfs + Qtz + Ap from core to ri 相似文献
15.
I. I. Likhanov V. V. Reverdatto P. S. Kozlov V. V. Khiller 《Doklady Earth Sciences》2013,450(1):556-561
Chemical mapping and in situ dating of U-Th-rich minerals in zoned garnets from gneisses of the Garevka metamorphic complex were used to constrain multiple metamorphic events in the Transangarian Yenisei Ridge. The data provide supporting evidence for three distinct metamorphic stages. The first episode occurred as a result of the Grenville orogeny during the Late Mesozoic and Early Neoproterozoic (1050–850 Ma) and was marked by low-pressure zoned metamorphism and a metamorphic field gradient with dT/dH = 20?30°C/km typical of orogenic belts. At the second stage, the rocks experienced Late Riphean (801–793 Ma) syn-collisional medium-pressure metamorphism with a low metamorphic field gradient (dT/dH ≤ 10°C/km). The final stage evolved as a synexhumation dynamic metamorphism (785–776 Ma) with dT/dH ≤ 12°C/km and reflected rapid exhumation of rocks in shear zones. The sequence of collisional events within the western margin of the Siberian craton affected by the Valhalla orogen suggests that Siberia and cratons of the North Atlantic region were in close proximity to one another at about 800 Ma, which is supported by recent paleomagnetic reconstructions. 相似文献
16.
N. A. Kulyukina P. L. Tikhomirov V. O. Yapaskurt 《Moscow University Geology Bulletin》2013,68(2):89-95
The metamorphic rocks of the Kuekvun uplift are gneisses and schists that developed after Mid-Paleozoic sedimentary sequences, which consist mostly of terrigenous rocks with minor amounts of intermediate to mafic igneous rocks and subordinate carbonates. Two plagiogneiss samples that were selected for detailed analysis were taken from the axial part and flanks of the uplift. The mineral paragenesis and composition of coexisting garnet, biotite, and staurolite indicate a metamorphic temperature of 560–600°C and pressure of 2.5–4 kbar, corresponding to a depth of 8–12 km. These conditions suggest a relatively high geothermal gradient (about 60°C/km), approaching that for contact metamorphic aureoles. Garnets from the axial zone and flanks of the uplift display a similar zoning pattern. The difference is the presence of compositionally contrasting Ca-rich rims in garnets from the axial zone. These rims may be either the result of zoning within the entire metamorphic complex or a late local overprint, e.g., crystallization of granitic plutons, which are common within the study area. 相似文献
17.
天山东段尾亚地区麻粒岩相变质岩存在的矿物化学证据 总被引：3，自引：0，他引：3
本文根据天山东段尾亚地区麻粒岩的主要造岩矿物斜方辉石、单斜辉石、黑云母、石榴子石和斜长石的电子探针分析结果,重点研究了尾亚麻粒岩各主要造岩矿物的化学成分特点,并且讨论其对变质作用温度压力条件的指示意义。矿物化学的研究结果表明,变质作用峰期达到了中压麻粒岩亚相。 相似文献
18.
S.A. Drury 《Chemical Geology》1973,11(3):167-188
The metamorphism and geochemistry of the major components of a small area of granulite facies rock are described and discussed, and a chemical model for the evolution of anomalous trace element distributions in such materials is suggested. The local complex was subjected to medium to high pressure granulite facies metamorphism between 2,900 and 2,600 m.y. All the analysed granulite facies rocks from Tiree; acid to intermediate gneisses, basic metamorphic rocks, and granitic rocks, have anomalous chemistries, being depleted in K, Rb, Nb, Y and Th, and have high K/Rb, Ba/Rb and Ca/Y ratios, and very low K/Ba and Rb/Sr ratios relative to normal portions of the upper continental crust. The gneisses seem to have been enriched in Ba and Sr.The chemical features of the rocks are considered to reflect their stable mineral assemblages in the granulite facies, and to be representative of deep-level crustal materials. The geochemical peculiarities of the complex may have been largely controlled by an upward intergranular diffusion, or “degassing” caused by high-grade metamorphism. It is suggested that such diffusion may have been active at the crust/upper mantle interface, some diffused material of mantle origin accounting for certain chemical oddities typical of Lewisian and some other Precambrian granulite facies rocks. 相似文献
19.
Dr. Peter H. Thompson 《Contributions to Mineralogy and Petrology》1973,42(1):63-80
Although regional mineral zoning in pelitic rocks has been described in numerous metamorphic terrains, relatively little is known about zoning in carbonate-bearing rocks. Regional metamorphism has resulted in a distinctive sequence of mineral zones in calcareous rocks (containing Fe, K and Al) of the Lessard Formation in the Bishop Corners-Madoc area, Grenville Province, Canada. The variation in metamorphic grade represented by the mineral zoning is attributed to a gradient in physical conditions (mainly temperature) at the time of metamorphism.In areas where pelitic schist and siliceous dolomite marble are rare or restricted in distribution, the mineral zones and isograds in impure calcareous rocks provide an alternative to conventional isograds for evaluating variations in metamorphic grade. In a metamorphic terrain where all three rock types occur, comparison of these isograds to those in pelitic and siliceous dolomite rocks results in a more accurate assessment of the distribution of isotherms and may provide some insight into the properties of the metamorphic fluid phase. 相似文献
20.
吉南新太古代泥质片麻岩出露于龙岗岩群四道砬子河岩组中,本文通过系统的岩相学、矿物化学、激光拉曼和锆石U Pb同位素年代学等分析,研究其变质演化特点、变质作用时代及构造意义.结果表明:龙岗岩群四道砬子河岩组泥质片麻岩记录了３个变质演化阶段,其中峰前期进变质阶段(M１)的矿物组合为石榴石＋黑云母＋斜长石＋石英＋白云母;峰期变质阶段(M２)的矿物组合为石榴石＋矽线石＋钾长石＋黑云母＋斜长石＋石英,达到麻粒岩相;峰后期退变质阶段(M３)以矽线石转变为蓝晶石为特征标
志,矿物组合为蓝晶石＋石榴石＋黑云母＋斜长石＋石英＋白云母.变质矿物地质温压计限定其变质作用,峰前期(M１)T 为４６８~５１５ ℃,p 为(３．８~４．３)×１０５ kPa;峰期(M２)T 为７０３~７６０ ℃,p 为(６．６~７．１)×１０５kPa;峰后期(M３)T 为５５２~５９１℃,p 为(５．５~６．０)×１０５kPa;具有典型的近等压冷却型逆时针变质作用p T 演化轨迹特征,可能是在地幔柱与岩石圈相互作用的环境中变质作用与大量的幔源岩浆底侵作用有关.LA ICP MS锆石U Pb定年结果显示麻粒岩相变质作用时代为２４９５~２４４２Ma,属于新太古代变质热事件产物. 相似文献