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1、單擊以編輯母版標(biāo)題樣式,單擊以編輯母版文本樣式,第二級(jí),第三級(jí),第四級(jí),第五級(jí),*,變質(zhì)作用期次及溫壓條件的確定,一、成分共生圖解和組分分析,1.,礦物組合及其確定標(biāo)志,在共生分析中，把一定化學(xué)成分巖石達(dá)到化學(xué)平衡時(shí)的礦物成分稱為,礦物組合,（,mineral assemblage,）或,礦物共生組合,（,mineral paragenesis,）,(P311),。,確定礦物共生組合的主要標(biāo)準(zhǔn),（,1,）一個(gè)礦物共生組合中各種礦物相互接觸；,（,2,）一個(gè)礦物共生組合的各礦物，相互間無(wú)反應(yīng)和交代現(xiàn)象；,（,3,）一個(gè)礦物共生組合中，同種礦物的化學(xué)成分及光性特征應(yīng)相近。如有環(huán)帶，則其邊部化學(xué)成分

2、及光性特征近似；,（,4,）一個(gè)礦物共生組合中的一對(duì)礦物之間元素的分配符合,Nernst,分配定律，即各處元素的分配系數(shù)近相等；,（,5,）礦物共生組合中礦物共生關(guān)系應(yīng)符合礦物相律，即礦物相數(shù)不超過(guò)惰性組分?jǐn)?shù)。,共生與共存,共生與共存是兩個(gè)完全不同的概念。,共存：,具有不同物理特征和,/,或化學(xué)特征的,相，,同時(shí)間、空間呈集合體存在，相之間的關(guān)系不一定服從熱力學(xué)定律。,共生：,同時(shí)空呈集合體存在的,相，,在相同物理化學(xué)條件下形成，并達(dá)到熱力學(xué)平衡。體系的內(nèi)能最低。,變質(zhì)相與變質(zhì)相系列,變質(zhì)相：,Eskola,（,1920,）,：一個(gè)變質(zhì)相是指類似的溫度、壓力條件下達(dá)到化學(xué)平衡的所有巖石總和,(

3、,不論其結(jié)晶方式），一個(gè)變質(zhì)相內(nèi)部，隨著巖石總體化學(xué)成分的改變，其礦物組合作有規(guī)律的改變。,Fyfe and Turner,（,1966,）,：一個(gè)變質(zhì)相是指一定的溫度、壓力區(qū)間內(nèi)的一整套變質(zhì)礦物共生組合，它們?cè)跁r(shí)間上、空間上反復(fù)出現(xiàn)并緊密地伴生在一起，一個(gè)變質(zhì)相內(nèi)部其礦物組合與巖石總體化學(xué)成分之間有著固定的、因而也是可以預(yù)測(cè)的對(duì)應(yīng)關(guān)系。,Turner 1981,年提出變質(zhì)相的分類,接觸變質(zhì)相：,（以溫度增高為序）鈉長(zhǎng)綠簾角巖相，普通角閃石角巖相 ，輝石角巖相，透長(zhǎng)石相。,區(qū)域變質(zhì)相,:,沸石相，葡萄石,綠纖石相 ，綠片巖相，藍(lán)閃石,硬柱石相，綠簾角閃巖相，角閃巖相，麻粒巖相，榴輝巖相,接觸變

4、質(zhì)巖相,1.,鈉長(zhǎng)綠簾角巖相（,AEH,）：,低溫,溫度約為,300-400,。,C,，壓力,0.1-0.4GPa,特征礦物組合：鈉長(zhǎng)石,+,綠簾石,+,透閃石或陽(yáng)起石,。沒(méi)有鈣質(zhì)斜長(zhǎng)石和鋁質(zhì)角閃石。鐵質(zhì)堇青石和黑云母出現(xiàn)于低溫部分，紅柱石出現(xiàn)溫度稍高，有時(shí)又葉蠟石。特征巖石是斑點(diǎn)板巖。,2.,普通角閃石角巖相（,HH,）：,中溫,溫度約,400-650,。,C,，壓力為,0.1-0.3GPa,特征礦物組合：斜長(zhǎng)石,+,普通角閃石,可以有透輝石，而沒(méi)有斜方輝石。變質(zhì)泥質(zhì)巖與長(zhǎng)英質(zhì)巖石中紅柱石，堇青石不與鉀長(zhǎng)石共生。,3.,輝石角巖相（,PH,）,:,高溫,溫度約,650-800,。,C,，壓力

5、不超過(guò),0.2GPa,夕線石，正長(zhǎng)石，,紫蘇輝石,或硅灰石為標(biāo)志礦物,白云母,+,石英不穩(wěn)定。紅柱石，堇青石，夕線石開(kāi)始與正長(zhǎng)石穩(wěn)定共存。特征礦物組合,:,斜長(zhǎng)石,+,透輝石,+,紫蘇輝石,4.,透長(zhǎng)石相（,S,）,:,極高溫溫度約,800-1100,。,C,，壓力極低，,0.02-0.08GPa,黃長(zhǎng)石，鈣鎂橄欖石，斜硅鈣石和透長(zhǎng)石等為特征礦物,特征礦物組合,:,斜長(zhǎng)石,+,普通輝石,+,易變輝石,。,Facies of low pressure,Albite-epidote hornfels, hornblende hornfels, and pyroxene hornfels facie

6、s: contact metamorphic terranes and regional terranes with very high geothermal gradient.,Metamorphic Facies,Sanidinite facies is rare- limited to xenoliths in basic magmas and the innermost portions of some contact aureoles adjacent to hot basic intrusives,區(qū)域變質(zhì)巖相,沸石相,(Z,或,ZE),：很低溫溫度約,200-300,。,C,，壓

7、力為,。特征礦物組合：鈉長(zhǎng)石,+,濁沸石,+,綠泥石,+,葡萄石,石英。,葡萄石,-,綠纖石相（,PP,）：很低溫溫度約,360-400,。,C,，壓力為,。特征礦物組合：,鈉長(zhǎng)石,+,葡萄石,+,綠纖石,+,綠泥石,多硅白云母,石英。,藍(lán)閃石,-,硬柱石片巖相（,GL,）：很低溫溫度,200-450,。,C,，壓力,0.3-0.8GPa.,特征礦物組合：（低壓）硬柱石,+,鈉長(zhǎng)石,+,綠泥石；（高壓）藍(lán)閃石,+,硬柱石,+,硬玉質(zhì)輝石,+,石英。是一個(gè)范圍很寬的低溫高壓變質(zhì)相，有時(shí)含有文石，完全不含黑云母。壓力有時(shí)可達(dá)到,1GPa,或更高。,4.,綠片巖相,(GS,）,:,低溫,溫度約,40

8、0-500,。,C,，壓力。特征礦物組合：（泥質(zhì)巖石）鈉長(zhǎng)石,+,綠簾石,+,白云母,+,綠泥石,+,石英 （基性巖石）鈉長(zhǎng)石,+,綠簾石,+,綠泥石,+,陽(yáng)起石；,高溫部分出現(xiàn)黑云母，高壓部分出現(xiàn)黑硬綠泥石，硬綠泥石和鐵鋁榴石。葉蠟石和硬綠泥石等不與鉀長(zhǎng)石共生。,5.,綠簾角閃巖相,(EA):,低溫,特征礦物組合：鈉長(zhǎng)石,+,綠簾石,+,普通角閃石（,+,鐵鋁榴石）,.,低壓條件下，鈣質(zhì)斜長(zhǎng)石的形成溫度低于普通角閃石時(shí)，便不能生成綠簾角閃巖相的共生。而形成斜長(zhǎng)陽(yáng)起石相。,6.,角閃巖相,(A,或,AM):,中溫溫度約,500-700,。,C,，壓力,0.3-0.8GPa,普通角閃石和斜長(zhǎng)石的

9、共生是本相的標(biāo)志,可以有透輝石沒(méi)有斜方輝石。泥質(zhì)巖中除了石英，白云母和黑云母外，低壓相系含紅柱石，堇青石和夕線石，中壓相系含十字石，藍(lán)晶石和鐵鋁榴石。高溫部分夕線石，鐵鋁榴石開(kāi)始與正長(zhǎng)石穩(wěn)定共生。,7.,麻粒巖相,(G):,高溫溫度,700-900,。,C,，壓力,0.3-1.2GPa,出現(xiàn)斜方輝石為標(biāo)志巖石主要由無(wú)水礦物所組成，少量黑云母和普通角閃石一般是富,Ti,的變種。,8.,榴輝巖相,(E):,高壓溫度,300-900,。,C,，壓力大于,1GPa,特征礦物組合：綠輝石,+,石榴子石不含長(zhǎng)石。一般呈不大的塊體在其它巖石中作為包體。溫度范圍很寬，壓力極大。,變質(zhì)相系,接觸變質(zhì)相系,:,d

10、T/dP=80,硅灰石，堇青石，紅柱石，（基本不含硅線石，不含十字石）,低壓區(qū)域變質(zhì)相系, dT/dP=80-40,紅柱石，硅線石，堇青石，（不含硅灰石，藍(lán)晶石，基本不含十字石）,中壓區(qū)域變質(zhì)相系, dT/dP=20-40,濁沸石，藍(lán)晶石，硅線石，十字石（不含紅柱石，堇青石，藍(lán)閃石，硬玉）,高壓區(qū)域變質(zhì)相系, dT/dP=20-5,硬柱石，藍(lán)晶石，藍(lán)閃石，硬玉（不含硅線石，濁沸石）,Fig. Temperature-pressure diagram showing the three major types of metamorphic facies series proposed by Mi

11、yashiro (1973, 1994).,Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.,變質(zhì)相與變質(zhì)相系列,變質(zhì)相系列：,同一地區(qū)通常不止一個(gè)變質(zhì)相，可以由許多不同的變質(zhì)相組成，構(gòu)成變質(zhì)相的系列；并且不同地區(qū)甚至同一地區(qū)不同地段變質(zhì)相系列不一樣。最著名的是本世紀(jì),50,年代末期，日本地質(zhì)學(xué)家都城秋穗在研究日本,三波川帶,和,領(lǐng)家?guī)?時(shí)，發(fā)現(xiàn)同一地區(qū)可以存在兩個(gè)不同的變質(zhì)相組合。他指出，,在變質(zhì)帶中，從低溫向高溫的的變化可以定義為一個(gè)相系列，或者稱作變質(zhì)相系,。并且他認(rèn)為,每

12、一種特定的變質(zhì)相系列都反映了各自的特定地?zé)崽荻阮愋秃退?jīng)歷的事件和演化進(jìn)程,，這就是變質(zhì)相系列的實(shí)質(zhì)。,變質(zhì)相與變質(zhì)相系列,(1),大體上的等物理系，標(biāo)志是一系列特征的礦物共生組合,(2),變質(zhì)相是由變質(zhì)反應(yīng)來(lái)標(biāo)定界線,(3),時(shí)間上、空間上反復(fù)出現(xiàn)是指同一變質(zhì)相的巖石在不同時(shí)間，不同地區(qū)經(jīng)常重復(fù)出現(xiàn)，并伴隨在一起。,2) Facies of medium pressure,Most metamorphic rocks now exposed belong to the,greenschist,amphibolite, or,granulite,facies,The,greenschist,a

13、nd,amphibolite,facies conform to the “typical” geothermal gradient,Metamorphic Facies,Metamorphic Facies,Zeolite,and,prehnite-pumpellyite,facies are thus not always represented, and the,greenschist,facies is the lowest grade developed in many regional terranes,4) Facies of low grades,Rocks often fai

14、l to recrystallize thoroughly at very low grades, and equilibrium is not always attained,Metamorphic P-T-t paths may be addressed by:,1) Observing partial overprints of one mineral assemblage upon another,The relict minerals may indicate a portion of either the prograde or retrograde path (or both)

15、depending upon when they were created,Pressure-Temperature-Time (P-T-t) Paths,Metamorphic P-T-t paths may be addressed by:,2) Apply geothermometers and geobarometers to the core vs. rim compositions of chemically zoned minerals to document the changing P-T conditions experienced by a rock during the

16、ir growth,Pressure-Temperature-Time (P-T-t) Paths,Chemical zoning profiles across a garnet from the Tauern Window. After Spear (1989),Fig.,Conventional P-T diagram (pressure increases upward) showing three modeled “clockwise” P-T-t paths computed from the profiles using the method of Selverstone,et

17、al,. (1984),J. Petrol., 25, 501-531 and Spear (1989). After Spear (1989),Metamorphic Phase Equilibria and Pressure-Temperature-Time Paths,. Mineral. Soc. Amer. Monograph 1.,Metamorphic P-T-t paths may be addressed by:,Even under the best of circumstances (1) overprints and (2) geothermobarometry can

18、 usually document only a small portion of the full P-T-t path,3) We thus rely on “forward” heat-flow models for various tectonic regimes to compute more complete P-T-t paths, and evaluate them by comparison with the results of the backward methods,Pressure-Temperature-Time (P-T-t) Paths,Classic view

19、: regional metamorphism is a result of deep burial or intrusion of hot magmas,Plate tectonics: regional metamorphism is a result of crustal thickening and heat input during orogeny at convergent plate boundaries (not simple burial),Heat-flow models have been developed for various regimes, including

20、burial, progressive thrust stacking, crustal doubling by continental collision, and the effects of crustal anatexis and magma migration,Higher than the normal heat flow is required for typical greenschist-amphibolite medium P/T facies series,Uplift and erosion has a fundamental effect on the geother

21、m and must be considered in any complete model of metamorphism,Pressure-Temperature-Time (P-T-t) Paths,Fig.,Schematic pressure-temperature-time paths based on heat-flow models. The Al,2,SiO,5,phase diagram and two hypothetical dehydration curves are included. Facies boundaries, and facies series fro

22、m Figs. 25-2 and 25-3.,Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.,Broad agreement between the forward (model) and backward (geothermobarometry) techniques regarding P-T-t paths,The general form of a path such as (a) therefore probably represents a typical rock

23、 during orogeny and regional metamorphism,Pressure-Temperature-Time (P-T-t) Paths,1. Contrary to the classical treatment of metamorphism, temperature and pressure do not both increase in unison as a single unified “metamorphic grade.”,Their relative magnitudes vary considerably during the process of

24、 metamorphism,Pressure-Temperature-Time (P-T-t) Paths,2. P,max,and T,max,do not occur at the same time,In the usual “clockwise” P-T-t paths, P,max,occurs much earlier than T,max,.,T,max,should represent the maximum grade at which chemical equilibrium is “frozen in” and the metamorphic mineral assemb

25、lage is developed,This occurs at a pressure well below P,max, which is uncertain because a mineral geobarometer should record the pressure of T,max,“Metamorphic grade” should refer to the temperature and pressure at T,max, because the grade is determined via reference to the equilibrium mineral asse

26、mblage,Pressure-Temperature-Time (P-T-t) Paths,3. Some variations on the cooling-uplift portion of the “clockwise” path (a) indicate some surprising circumstances,For example, the kyanite,sillimanite transition is generally considered a prograde transition (as in path a,1,), but path a,2,crosses the

27、 kyanite,sillimanite transition as temperature is,decreasing.,This may result in only minor replacement of kyanite by sillimanite during such a retrograde process,Pressure-Temperature-Time (P-T-t) Paths,Fig. 25-12a.,Schematic pressure-temperature-time paths based on a,crustal thickening,heat-flow mo

28、del. The Al,2,SiO,5,phase diagram and two hypothetical dehydration curves are included. Facies boundaries, and facies series from Figs. 25-2 and 25-3.,Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.,Fig. 25-14.,A typical Barrovian-type metamorphic field gradient an

29、d a series of metamorphic P-T-t paths for rocks found along that gradient in the field.,Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.,一、變質(zhì)巖原巖恢復(fù),1.,變質(zhì)巖原巖恢復(fù)的一般原則,a.,變余特征優(yōu)先原則,b.,巖套類比的原則,c.,等化學(xué)的原則,d.,惰性組分的原則,e.,相關(guān)性和趨勢(shì)性原則,變余結(jié)構(gòu)、構(gòu)造（沉積巖）,變余斑狀結(jié)構(gòu)（,a,）和變余砂狀結(jié)構(gòu)（,b,）,a.,綠泥片巖，原巖中輝石斑晶為綠泥石交代呈假象；,b.,變質(zhì)含礫石石英雜砂巖，碎屑為石英和石英巖，膠結(jié)物已變?yōu)榧?xì)小的絹云母、黑云母和石英。,變質(zhì)石英砂巖，遼寧。磨圓的石英顆粒之間分布的石英粘土已經(jīng)變質(zhì)為絹云母。,變余結(jié)構(gòu)、構(gòu)造（火成巖）,變余斑狀結(jié)構(gòu)（,a,）和變余砂狀結(jié)構(gòu)（,b,）,a.,綠泥片巖，原巖中輝石斑晶為綠泥石交代呈假象；,b.,變質(zhì)含礫石石英雜砂巖，碎屑為石英和石英巖，膠結(jié)物已變?yōu)榧?xì)小的絹云母、黑云母和石英。,B.,巖石化學(xué)、地球化學(xué)和副礦物,1.,巖石化學(xué),a. K2ONa2O,b.,圖解法,2.,地球化學(xué),3.,副礦物,a.,碎屑副礦物的有無(wú)和含量,b.,副礦物晶形及顏色,