【摘要】：仙霞巖體是浙北和皖南交界區(qū)域明顯受北東向?qū)W川-孝豐斷裂構(gòu)造帶控制的大巖體,其內(nèi)部巖性復(fù)雜,主要由早期中粒二長(zhǎng)花崗巖、巨斑狀二長(zhǎng)花崗巖和晚期中粗粒正長(zhǎng)花崗巖、細(xì)粒正長(zhǎng)花崗巖組成,后期有大量細(xì)晶巖、石英正長(zhǎng)巖、閃長(zhǎng)玢巖、安山巖、輝綠巖等脈巖侵入。鋯石U-Pb年齡數(shù)據(jù)顯示早期二長(zhǎng)花崗巖大約侵位于145.1~144.2Ma,晚期正長(zhǎng)花崗巖大約侵位于131.7~130.8Ma,后期輝綠巖脈侵位于128.3Ma。兩期巖石均具高SiO_2、高K_2O+Na_2O和低P_2O_5特征;早期二長(zhǎng)花崗巖為準(zhǔn)鋁質(zhì)、高鉀鈣堿系列巖石,稀土配分曲線強(qiáng)右傾,中等負(fù)Eu異常,富集Rb、Th、U、K,虧損Ba、Nb、Sr、P、Ti等特征;晚期正長(zhǎng)花崗巖為準(zhǔn)鋁質(zhì)-過(guò)鋁質(zhì)、鉀玄巖系列巖石,稀土配分曲線弱右傾、強(qiáng)負(fù)Eu異常,同樣富集Rb、Th、U、K,強(qiáng)虧損Sr、P、Ti等特征;均屬高分異I型花崗巖類。兩期巖石均具有相對(duì)高的(86Sr/87Sr)i值(0.70807~0.70988)和εNd(t)值(-8.87~-5.14),Nd二階段模式年齡為1.36~1.65Ga。成巖可能與古太平洋板塊俯沖角度的改變,構(gòu)造背景由中晚侏羅世(165±5~145±5Ma)的擠壓環(huán)境向早白堊世早期(145±5~125Ma)的伸展拉張環(huán)境轉(zhuǎn)變有關(guān),致使古老江南造山帶地殼物質(zhì)熔融并可能混染揚(yáng)子巖石圈地幔物質(zhì)形成的兩期巖漿經(jīng)高程度結(jié)晶分離作用先后侵位,也表明浙西北乃至華南地區(qū)晚中生代構(gòu)造轉(zhuǎn)換時(shí)間為145Ma左右,且在早白堊世發(fā)生了多期次伸展拉張作用。
[Abstract]:Xianxia rock mass is a large rock mass obviously controlled by the northeast Xuechuan-Xiaofeng fault structural belt in the border area between northern Zhejiang and southern Anhui. Its internal lithology is complex, mainly from the early medium-grain monzonitic granite. The macromacular monzonitic granite and the late middle coarse granitic syenite and fine granitic syenite are composed of a large number of fine crystal rocks, quartz syenite, diorite, andesite, diabase and other gangue intrusions in the later stage. Zircon U-Pb age data show that the early monzonitic granite was about 145.1 Ma, the late syenite granite was 131.7 Ma, and the later diabase vein invasion was 128.3 Ma. The rocks of the two stages are characterized by high SiO_2, high K 鈮，

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