摘要
红柱石是长英质岩石中常见的铝硅酸盐矿物,其成因分为变质、岩浆和转熔三类.变质成因红柱石主要存在于低级变泥质岩中,是白云母、石英、黑云母以及长石等矿物在低压条件下发生变质反应的产物.岩浆成因和转熔成因红柱石主要存在于过铝质花岗岩和混合岩浅色体中,其形成主要受控于岩浆体系中Al2O3含量和温压条件.岩浆的Al2O3过饱和有利于红柱石的形成,可以通过四个途径获得:准铝质或过铝质岩石的部分熔融、同化混染过铝质围岩、结晶分异以及岩浆与流体的相互作用等.红柱石在岩浆体系中结晶的温度为650~800℃,压力小于(4.5±0.5)×10^5kPa.本文系统总结了不同成因红柱石在矿物产状、包裹体、成分环带以及与所在寄主岩石的造岩矿物之间平衡关系上的特征,建立了区分不同成因红柱石的标志.喜马拉雅淡色花岗岩中常见红柱石,运用所总结的多种区分标志,推断其中半自形-自形红柱石主要为岩浆成因,少数为转熔成因,而他形红柱石(呈簇状集合体)可能是变泥质围岩的残留矿物.通过对高喜马拉雅结晶岩系的变质和部分熔融过程分析,淡色花岗岩原始岩浆产生于进变质-退变质早期的过程中,而由于此时岩浆体系的压力较高,难以出现红柱石的结晶.在岩浆上升侵位的过程中,随着温度和压力逐渐降低,加之矿物的结晶分离使得岩浆成分逐渐趋于过铝质,红柱石能够在此过程中结晶.同时,在岩浆上升侵位的过程中,不可避免发生的围岩同化混染也有可能造成围岩中的矿物通过转熔反应生成红柱石.
Andalusite,as a common aluminosilicate mineral in felsic rocks,can be divided into three types:metamorphic,magmatic and peritectic.Metamorphic andalusite mainly exists in metapelite and is a product of metamorphic reactions of minerals such as muscovite,quartz,biotite and feldspar under low pressure.Magmatic and peritectic andalusite mainly exists in peraluminous granite and migmatite,and its formation is mainly controlled by the temperature and pressure conditions and Al2 O3 content of the magmatic system.The supersaturation Al2 O3 can be obtained by four ways:partial melting of metaluminous or peraluminous source rocks,assimilation of peraluminous wall rock,fractional crystallization and the interaction between fluid and magma.The ranges of temperature and pressure of the andalusite crystallization field are 650~800℃and lower than(4.5±0.5)×105 kPa,respectively.This article systematically summarizes the differences of the andalusite in different genesis on the basis of the mineral occurence,inclusions,compositional zonation,and the equilibrium relationship with the intergrown rock-forming minerals,and establishes the indicator for determining the different genesis.Andalusite is commonly found in the Himalayan leucogranite,it is interpreted that the subhedral and euhedral ones mainly have the magmatic origin,and occasionally peritectic origin,and fine-grained anhedral andalusite as the clusters may be residual minerals from the metamorphic wall rock.Combined with the features of metamorphism and partial melting process of the High Himalayan Crystalline Sequence,leucogranite magmas were generated during the prograde metamorphism-early retrograde metamorphism.The primary high pressure of the magma system was not suitable for crystallization of andalusite.When the temperature and pressure gradually decrease,the magma will evolve to peraluminous due to the fractional crystallization,and the andalusite could be formed under this condition.Meanwhile,assimilation of wall rock is inevitable during magma ascent and emplacement,so it is possible that the andalusite could be generated by the peritectic reaction.
作者
何少雄
刘小驰
王佳敏
胡方泱
吴福元
He Shaoxiong;Liu Xiaochi;Wang Jiamin;Hu Fangyang;Wu Fuyuan(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing,100029,China;Innovation Academy for Earth Science,Chinese Academy of Sciences,Beijing,100029,China;College of Earth and Planetary Science,University of Chinese Academy of Sciences,Beijing,100049,China)
出处
《南京大学学报（自然科学版）》
CAS
CSCD
北大核心
2020年第6期774-787,共14页
Journal of Nanjing University（Natural Science）
基金
国家自然科学基金委基础研究中心项目(41888101)
中国科学院第二次青藏高原科考“资源能源现状与远景评估”专题(2019QZKK0802)
国家自然科学基金(41772058)
内生金属矿床成矿机制研究国家重点实验室开放研究基金(2018-LAMD-K06)。
