CAJ | 학술논문

柳洞岩体位于延边地区和龙市南部，大地构造位置上处于古洞河断裂西南侧，龙岗地块北缘，其岩性为二长花岗岩。为确定其侵位时代和大地构造环境，对柳洞岩体进行了系统的岩相学和年代学研究。N 6和N 7样品LA ICP MS锆石U Pb测年结果显示，其加权平均年龄分别为（118．63±0．69）Ma和（118．58±0．87）Ma。岩体具有高硅（w（SiO2）＝70．30％～76．30％）、富碱（w（Na2O＋ K2O）＝7．82％～8．52％）、富铝（w（Al2 O3）＝12．30％～15．50％）和低钛（w（TiO2）＝0．16％～0．29％）的特点，属于高钾钙碱性系列。A/CNK值为1．03～1．11，为弱过铝质岩石。分异指数（D I）为87．99～94．89，固结指数（S I）为2．39～5．31，反映了该岩体经历了高程度分异演化作用。δEu为0．63～0．92，具有中等铕负异常，LREE/HREE和（La/Yb）N 值分别为3．46～8．09和10．59～33．94，显示轻稀土元素相对富集、重稀土元素亏损的特点。柳洞岩体明显富集Cs、Rb、Ba、K等大离子亲石元素（LILE），同时亏损 Nb、Ta、Ti等高场强元素（HFSE）以及P元素。综合岩相学、年代学、岩石地球化学特征及区域地质资料，柳洞岩体具有高分异的高钾钙碱性I型花岗岩的特点，形成于后造山向伸展转换的体制环境下。
류동암체위우연변지구화룡시남부，대지구조위치상처우고동하단렬서남측，룡강지괴북연，기암성위이장화강암。위학정기침위시대화대지구조배경，대류동암체진행료계통적암상학화년대학연구。N 6화N 7양품LA ICP MS고석U Pb측년결과현시，기가권평균년령분별위（118．63±0．69）Ma화（118．58±0．87）Ma。암체구유고규（w（SiO2）＝70．30％～76．30％）、부감（w（Na2O＋ K2O）＝7．82％～8．52％）、부려（w（Al2 O3）＝12．30％～15．50％）화저태（w（TiO2）＝0．16％～0．29％）적특점，속우고갑개감성계렬。A/CNK치위1．03～1．11，위약과려질암석。분이지수（D I）위87．99～94．89，고결지수（S I）위2．39～5．31，반영료해암체경력료고정도분이연화작용。δEu위0．63～0．92，구유중등유부이상，LREE/HREE화（La/Yb）N 치분별위3．46～8．09화10．59～33．94，현시경희토원소상대부집、중희토원소우손적특점。류동암체명현부집Cs、Rb、Ba、K등대리자친석원소（LILE），동시우손 Nb、Ta、Ti등고장강원소（HFSE）이급P원소。종합암상학、년대학、암석지구화학특정급구역지질자료，류동암체구유고분이적고갑개감성I형화강암적특점，형성우후조산향신전전환적체제배경하。
The Liudong pluton is located in the southern Helong area of Yanbian area ,the southwest segment of Gudonghe fault and north margin of Longgang block .It’s composed of monzonitic granite . Systematic researches on petrography and geochronology have been carried out to determine the emplacement age and tectonic environment of the pluton .The LA ICP MS zircon U Pb dating yields the weighted mean age of (118 .63 ± 0 .69) Ma and (118 .58 ± 0 .87) Ma for N 6 and N 7 sample , respectively .The rock is weak peraluminous and belongs to the high potassium calc-alkaline series , characterized by high Si (70 .30% 76 .30% ) ,high alkali (7 .82% 8 .52% ) ,high aluminum (12 .30%15 .50% ) and low titanium (0 .16% 0 .29% ) ,with A/CNK value of 1 .03 1 .11 .Such geochemical characteristics as DI (87 .99 94 .89)and SI (2 .39 5 .31) indicate the rock experienced a highly fractionated evolving stage .The rock is of LREE enrichment (LREE/HREE=3 .46 8 .09) and HREE depletion ((La/Yb)N =10 .59 33 .94) .The Liudong pluton is characterized by the strong enrichment in large ion lithophile elements (LILE) ,such as Cs ,Pb ,Ba ,K ,depletion in high field-strength elements (HESE) ,such as Nb , Ta , Ti ,and P ,and middle negative Eu anomalies (δEu = 0 .63 ~ 0 .92) . Combining petrography , geochronology , rock geochemical characteristics , and regional geological material ,it can be concluded that the Liudong pluton belongs to the highly fractionated high-potassium calc-alkaline I-type granite and emplaced in the transferring stage from a post-orogenic to an extensional tectonic setting .