CAJ | 학술논문

位于北山北部红石山地区雀儿山群的火山岩主要为一套中酸性火山岩,以安山岩、英安岩和流纹岩为主,属钙碱碱性系列。地球化学研究表明：火山岩 SiO2含量较高(62.29%~75.74%),MgO 含量较低(<2.15%),全碱含量较高(Na2 O+K2 O 为6.24%~9.2%),且 K2 O/Na2 O<1。轻稀土元素(LREE)相对于重稀土元素(HREE)呈现较强富集[(La/Yb)N =2.94~6.36],轻稀土内部出现较强分馏[(La/Sm)N =1.94~3.33],并且具有相当明显的 Eu 负异常(0.50~0.90)；在微量元素方面,大离子亲石元素(LILE)相对高场强元素(HFSE)富集,具有明显的 Nb、Ta、P、Ti 相对亏损和 Ba、Th、Zr、Ce、Sm 相对富集。上述特征表明该火山岩形成于洋壳俯冲作用下的岛弧环境,可能与哈萨克斯坦板块和塔里木板块之间的古洋壳俯冲消减有直接的成因联系,在俯冲过程中洋壳含水流体引起上覆地幔物质的部分熔融,并在岩浆上升中经历了一定的分离结晶作用和上地壳物质的同化混染。
위우북산북부홍석산지구작인산군적화산암주요위일투중산성화산암,이안산암、영안암화류문암위주,속개감감성계렬。지구화학연구표명：화산암 SiO2함량교고(62.29%~75.74%),MgO 함량교저(<2.15%),전감함량교고(Na2 O+K2 O 위6.24%~9.2%),차 K2 O/Na2 O<1。경희토원소(LREE)상대우중희토원소(HREE)정현교강부집[(La/Yb)N =2.94~6.36],경희토내부출현교강분류[(La/Sm)N =1.94~3.33],병차구유상당명현적 Eu 부이상(0.50~0.90)；재미량원소방면,대리자친석원소(LILE)상대고장강원소(HFSE)부집,구유명현적 Nb、Ta、P、Ti 상대우손화 Ba、Th、Zr、Ce、Sm 상대부집。상술특정표명해화산암형성우양각부충작용하적도호배경,가능여합살극사탄판괴화탑리목판괴지간적고양각부충소감유직접적성인련계,재부충과정중양각함수류체인기상복지만물질적부분용융,병재암장상승중경력료일정적분리결정작용화상지각물질적동화혼염。
The volcanic rocks of Queershan Group,located in Hongshishan area,north of Beis-han,are mainly composed of intermediate-acid volcanics,andesites,dacite and rhyolite,which belong tocalc-alkaline series. Researches on the geochemistry suggest that,these volcanic rock-shave high SiO2 content (62.29%-75.74%,lower MgO content (<2.15%),relatively high al-kali content (Na2 O+K2 O=6.24%-9.2%),and K2 O/Na2 O<1. These rocksare enrich in LREE relative to HREE ((La/Yb)N =2.94-6.36),with a strong fractionation in LREE ((La/Sm)N =1.94-3.33),presenting a strong negative anomaly of Eu (0.50-0.90). In the aspect of trace ele-ments,these rocks are enrich in LILE more than HFSE,with relatively depletion of Nb,Ta,P and Ti,as well as the enrichment of Ba,Th,Zr,Ce and Sm. These geochemical characteristics approve that,these volcanic rocks formed in the island arc environment with the effect of oceanic crust subduction,which has a direct genetic relationship with the subduction of ancient oceanic crust between Kazakhstan plate and Tarim plate. During the process of subduction,the partial melting of the overlying mantle material was caused by the hydrous fluids of oceanic crust,and the product created by the rising magma has experienced a certain fractional crystallization and as-similation and contamination of upper crustal material.