麻粒岩相变质作用与花岗岩成因-Ⅰ:变质泥质岩/杂砂岩高温-超高温变质相平衡

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	麻粒岩相变质作用与花岗岩成因-Ⅰ:变质泥质岩/杂砂岩高温-超高温变质相平衡; Granulite facies metamorphism and petrogenesis of granite (Ⅰ) : Metamorphic phase equilibria for HT-UHT metapelites/greywackes
	魏春景 ; 朱文萍
刊名	岩石学报
	2016
关键词	麻粒岩高温-超高温变质作用变质相平衡泥质岩与杂砂岩 Granulite HT-UHT metamorphism Metamorphic phase equilibria Metapelites/greywackes PARTIAL MELTING EQUILIBRIA NORTH CHINA CRATON CONTINENTAL-CRUST PRESSURE MIGMATITES SYSTEMS KFMASH
英文摘要	麻粒岩相岩石作为洞察下地壳的窗口一直备受重视.二十世纪九十年代以来麻粒岩研究的一个重要进展是利用变质相平衡的定量研究方法模拟岩石中所发生的深熔变质反应、熔体成分变化、及熔体丢失对变质矿物组合的影响等.本文利用KASH、NKASH和KFMASH等简单体系的相平衡关系,做出P-T投影图、组分共生图解和基于固定全岩成分的P-T视剖面图解,并结合有关实验岩石学结果,讨论了高温和超高温条件下变质泥质岩和杂砂岩中的变质熔融反应、矿物组合、全岩成分与P-T条件之间的相互关系.多数变质泥质岩和杂砂岩中饱和流体固相线熔融反应可利用NKASH体系中有水流体参与的熔融反应模拟,在没有外来流体注入时,这些反应可形成＜ 3mol％熔体.在不同体系中白云母脱水熔融反应型式及其P-T条件不同,如在NKASH和KFMASH体系中模拟计算的白云母脱水熔融反应与相应的实验结果相似,分别控制了白云母分解熔融的温度下限和上限;白云母的分解温度会随着其中Fe、Mg和Ti含量的增加而升高,也随着共生斜长石中钙长石组分增加而升高,泥质岩中白云母脱水熔融可以形成～ 10mol％熔体.在KFMASH体系中黑云母脱水熔融反应表现为4条单变反应,其理论计算的温度比实验模拟的结果低一些.在NCKFMASH体系或实际岩石中黑云母脱水熔融反应为滑动反应,如NCKFMASH体系中黑云母从其开始熔融到最后消失在泥质岩中可跨越～100℃,在杂砂岩中可跨越30～50℃.黑云母的稳定温度随着镁值升高而升高,其稳定上限受钛影响更大,黑云母脱水熔融可以形成超过30mol％～40mol％熔体.KFMASH体系中的相平衡模拟表明以出现斜方辉石+夕线石和假蓝宝石为特征的超高温组合易于出现于富镁泥质岩中,而对正常成分泥质岩在达到1000℃的超高温条件下,主要出现石榴石+夕线石(即夕线榴),该组合在更高温度反应形成假蓝宝石+尖晶石.利用饱和水固相线反应和白云母与黑云母分解反应可以更好地限定不同的变质相.如中压和低压条件下低角闪岩相和高角闪岩相的界限可利用NKASH体系中有水流体和白云母参与的熔融反应和亚固相线条件下的白云母分解反应限定;实验确定的泥质岩中黑云母开始熔融与消失的反应可分别用于限定高角闪岩相与(正常)麻粒岩相的界限,以及(正常)麻粒岩相和超高温麻粒岩相的界限.因此,从矿物组合角度,正常麻粒岩相可限定在黑云母开始熔融到完全消失的温度范围,超高温麻粒岩相可限定在黑云母消失(有石英存在)之后的温度范围.; Granulites have attracted much attention as a window of probing the lower crust tectonic evolution. Since 1990s one of the most important advances in the study of granulite is quantitatively modeling the melting reactions, melt compositions, melt loss and its influence on mineral assemblages in high-grade rocks. Based on a series of P-T projections, compatibility diagrams and qualitative P-T pseudosections for fixed bulk-rock compositions in the simple systems involving KASH, NKASH and KFMASH, and available experimental results, discussions were presented in this paper in terms of the relations among melting reactions, mineral assemblages, bulk-rock compositions and P-T conditions for the meta-pelitic and greywacke rocks under HT-UHT conditions. The fluid-saturated solidus reactions for most meta-pelites/greywackes can be modeled by the fluid involving reactions in the NKASH system, which can produce melt of < 3mol% without fluid infiltration. The P-T conditions of muscovite dehydration melting reactions vary in different systems. For example, muscovite melting reactions calculated in the systems NKASH and KFMASH, which are in good accordance with the relevant experimental results, constrain respectively the lower and upper temperature limits of muscovite breakdown. The muscovite breakdown temperature may increase as increasing its Fe, Mg and Ti contents, or the anorthite content in coexisting plagioclase. Muscovite melting can produce melt of similar to 10mol% in metapelites. In the system KFMASH biotite dehydration melting involves four univariant reactions, with calculated temperature conditions somewhat lower than the experimental results. These biotite melting reactions are continuous in the system NCKFMASH, covering a temperature range of similar to 100 degrees C in metapelites and 30 similar to 50 degrees C in metagreywackes. The biotite breaking temperature may increase as increasing its Mg-#; and the upper temperature limit is greatly influenced by the involvement of Ti. Biotite melting can produce melt of 30mol% similar to 40mol% in metapelites. Phase modelling in the system KFMASH suggests that the diagnostic UHT assemblages with orthopyroxene + sillimanite, or sapphirine can easily appear in Mg-rich metapelites, and most metapelites of normal composition can only have the assemblage of garnet + sillimanite even under UHT conditions of 1000 degrees C, which can transform into sapphirine + spinel under much higher temperatures. The fluid-saturated solidus reactions, and muscovite and biotite breaking reactions can be used to define the boundaries between metamorphic facies. For instance, the fluid- and muscovite-involving melting reactions and the subsolidus muscovite breakdown reaction in the system NKASH can well define the boundary between low- and high-amphibolite facies under medium and low pressures. The experimentally constrained initial melting and disappearance reactions of biotite in metapelites can be used, respectively, to define the boundaries between high-amphibolite and (normal) granulite facies, and between (normal) granulite and UHT granulite facies. Consequently, in the context of mineral assemblages in metapelites, the (normal) granulite facies may cover a temperature range from the start of biotite melting to its disappearance, and the UHT granulite facies can be defined to the temperature conditions above biotite disappearance.; 国家自然科学基金项目; SCI(E); 中文核心期刊要目总览(PKU); 中国科技核心期刊(ISTIC); 中国科学引文数据库(CSCD); cjwei@pku.edu.cn; 6; 1611-1624; 32
语种	中文
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/492229]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	魏春景,朱文萍. 麻粒岩相变质作用与花岗岩成因-Ⅰ:变质泥质岩/杂砂岩高温-超高温变质相平衡, Granulite facies metamorphism and petrogenesis of granite (Ⅰ) : Metamorphic phase equilibria for HT-UHT metapelites/greywackes[J]. 岩石学报,2016.
APA	魏春景,&朱文萍.(2016).麻粒岩相变质作用与花岗岩成因-Ⅰ:变质泥质岩/杂砂岩高温-超高温变质相平衡.岩石学报.
MLA	魏春景,et al."麻粒岩相变质作用与花岗岩成因-Ⅰ:变质泥质岩/杂砂岩高温-超高温变质相平衡".岩石学报 (2016).