摘要
东天山星星峡白石头泉合黄玉花岗岩岩体在露头上显示很好的岩性分带,从下至上依次为:淡色花岗岩(a带),含天河石花岗岩(b带),天河石花岗岩(c带),含黄玉天河石花岗岩(d带)以及黄玉钠长花岗岩(e带)。在岩体中存在众多的天河石伟晶岩脉和透镜体,在岩体围岩中还可见到黄玉钠长石脉。岩体的结晶和固结是由下往上进行的。石英和黄玉是最早从熔体中晶出的矿物相,而天河石是由富含流体的残余熔体填隙结晶或与先存矿物反应而成。从a带到e带总的趋势是:(1)随着石英斑晶粒径渐大和晶形渐好,岩石结构从等粒状变为似斑状;(2)天河石和黄玉富集于最上部的三个带;(3)随着Li和(Al+Ti)含量的增加,白色云母成份从a,b,c带的铁叶云母演化到d带的铁锂云母;(4)F、H_2O、Al_2O_3和Na_2O含量增加,而SiO_2、FeO、K_2O含量和Fe^(2+)/Fe^(3+)比值降低,且在标准矿物Qz-Ab-Or图解上,成分投影向Ab顶角移动;(5)Co、Ni、Cr、W、Nb、Zr、U、Th、Y、含量和K/Rb、Zr/Hf比值降低,而F、Li、Rb、Ga、V、Sn含量和Rb/Cs、Ga/Al、La_(CN)/Lu_(CN)比值加大;(6)δ^(18)O从9.25‰～9.75‰下降到7.32‰;(7)石英熔体包裹体均一法温度从860℃～810℃下降到680℃～660℃。上述岩性和地球化学分带是由于岩浆中较高的F和H_2O含量,促进了分离结晶和流体搬运的?
The Baishiquan topaz-bearing amazonite granite pluton in eastern Tianshan exhibits five well-exposed lithological zones, which, gradational from the lowest level, are leucogranite zone (zone a), amazonite-bearing granite zone (zone b), amazonite granite zone (zone c), topaz-bearing amazonite granite zone (zone d) and topaz albite granite zone (zone e). Numerous veins and lenses of amazonite pegmatite occur in the pluton, and topaz albitite veinlets are found cutting the confining rocks to the intrusion. Crystallization and consolidation of the intrusion proceeds upwards from the lower zones. Quartz and topaz are the earliest phases that crystallized from the melt, whereas amazonite is formed from a fluid-rich residual magma, by interstitial fillig and replacing earlier minerals. General trends from zone a to zone e are: (1) With quartz phenocrysts progressively larger in size and better in crystal perfectness, the rock texture changes from equigranular to porphyroidal; (2) Amozonite and topaz are enriched in the uppermost three zones; (3) With increasing Li and (Al+Ti), white mica evolves from siderophyllite in zone a, b and c to zinnwaldite in, zone d; (4) F, H2O, Al2O3, and Na2O increase, SiO2, FeO, K2O and Fe3+/Fe2+ decrease, and. plots of normative composition on the Qz-Ab-Or diagram move towards the Ab apex; (5) Co, Ni, Cr, W, Nb, Zr, U, Th, Y, K/Rb and Zr/Hf decrease, whereas F, Li, Rb, Ga, V, Sn, Rb/Cs, Ga/Al and La-CN/Lu-CN increase; (6) delta(18)O decrease from 9.25similar to9.75parts per thousand in zone a to 7.32parts per thousand in zone e; (7) Homogenization temperatures of melt inclusions in quartz decrease from about 860degreessimilar to810degrees for zone a to about 680degreessimilar to660degrees for zone e. Such petrological and geochemical zoning was caused by higher F and H2O contents of the magma, which facilitated fractional crystallization and fluid transfer.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2003年第4期585-600,共16页
Acta Petrologica Sinica
基金
国家重点基础研究发展规划项目(编号:2001CB409802)成果
关键词
花岗岩
氟
铷
黄玉
天河石
天山
新疆
granite
fluorine
rubidium
topaz
amazonite
Tianshan
Xinjiang
