本文選題：榍石　切入點(diǎn)：金紅石　出處：《巖石學(xué)報(bào)》2017年08期 　論文類型：期刊論文

【摘要】：金紅石邊緣形成榍石冠狀邊結(jié)構(gòu)在變質(zhì)中-基性巖中普遍存在,是金紅石與退變質(zhì)流體攜帶的SiO_2與CaO作用的結(jié)果,反應(yīng)形成的榍石微量元素特征受到金紅石和流體的共同影響。雅魯藏布江縫合帶中角閃巖LZ06-04在抬升過程經(jīng)歷近等溫降壓退變質(zhì)作用,石榴子石分解導(dǎo)致同一樣品中含石榴子石部分與不含石榴子石部分的退變質(zhì)流體成分的差異。兩種流體分別與金紅石反應(yīng),對(duì)應(yīng)形成的榍石具有相似的Nb、Ta含量和Nb/Ta比值特征,但截然不同的REE特征。榍石的Nb、Ta來源于金紅石,殘余金紅石與含水流體再平衡Nb、Ta的分配系數(shù)增大,且D_(Nb)~(Rt/Fluid)≥D_(Ta)~(Rt/Fluid);雖然Nb和Ta在含水流體中都表現(xiàn)為不活動(dòng)元素,但相對(duì)于Nb,Ta在含水流體中活動(dòng)性較高。榍石的Zr-Hf體系特征受到鋯石、石榴子石等礦物的綜合影響,并且Zr-Hf在含水流體中表現(xiàn)出比Nb-Ta更高的活動(dòng)性。榍石的REE特征受流體中REE特征、榍石與流體配分系數(shù)以及共生礦物的影響。在巖漿或變質(zhì)體系,榍石形成過程中,REE富集礦物(如石榴子石、鋯石、褐簾石、獨(dú)居石、磷灰石等)形成或分解將影響榍石的REE分布特征或形成REE環(huán)帶結(jié)構(gòu)。含水流體中金紅石退變質(zhì)形成榍石反應(yīng)的進(jìn)行受流體中TiO_2、CaO和SiO_2活度的影響。因此榍石常見于鈣堿性巖漿巖、富Ca基性變質(zhì)巖和矽卡巖中。流體中CaO活度的變化影響榍石的形成,進(jìn)而影響Ti、Nb、Ta在流體中的運(yùn)移能力。俯沖板片產(chǎn)生流體在交代上覆富Ca地幔楔物質(zhì)過程中形成榍石殘留同樣可以造成部分熔融體具有虧損HFSE特征。
[Abstract]:The formation of sphene coronal edge structure at the rutile edge is common in metamorphic basic rocks, which is the result of the interaction between rutile and retrograde fluid carrying SiO_2 and CaO. The trace element characteristics of sphene formed by the reaction are influenced by both rutile and fluid. The amphibolite LZ06-04 in the Yalu Zangbo suture zone experienced near isothermal depressurization retrograde metamorphism during the uplift process. The decomposing of pomegranate leads to the difference of retrograde fluid composition between the part containing pomegranate and the part without pomegranate. The two fluids react with rutile respectively. The corresponding sphene has similar characteristics of NB Ta content and Nb/Ta ratio. However, the REE characteristics of sphene are quite different. The NB / Ta of sphene is derived from rutile, and the partition coefficient of residual rutile and water bearing fluid reequilibrium NB / Ta increases, and the D T / T / Fluid) 鈮，

本文編號(hào)：1621134