CAJ | 학술논문

内蒙古阿拉善地块北缘塔木素地区酸性侵入岩发育,主要岩性为黑云母花岗岩、花岗闪长岩、二长花岗岩、英云闪长岩,其中花岗闪长岩、英云闪长岩、二长花岗岩构成塔木素地区侵入岩的主体,岩体侵入晚石炭世—早二叠世阿木山组,又被白垩系、侏罗系不整合覆盖,区域上呈近东西向展布.采用LA-ICP-MS技术,测得内蒙古阿拉善右旗塔木素地区的塔木素二长花岗岩和笋布尔英云闪长岩中锆石的206Pb/238U年龄分别为264.2±3.3Ma和273.0±3.3Ma,这2个年龄被解释为各自的侵位年龄,即二者均形成于中二叠世.花岗闪长岩、二长花岗岩和英云闪长岩在SiO2-K2O图解中落入钙碱系列和高钾钙碱性系列,A/CNK值分别为0.874~1.01、1.06~1.54和0.91~1.03;Ba、Rb、Th、K等大离子亲石元素富集,Nb、Ta、P、Ti等高场强元素相对亏损;稀土元素总量分别介于156.99×10-6~212.87×10-6、126.92×10-6~212.98×10-6和128.13×10-6~214.5×10-6之间,均呈负Eu异常;在构造环境Rb-(Yb+Nb)和Rb-(Yb+Ta)判别图解中均落入火山弧花岗岩区.结合区域背景分析,阿拉善北缘在早二叠世时可能存在与弧物质有关的岩浆活动.
내몽고아랍선지괴북연탑목소지구산성침입암발육,주요암성위흑운모화강암、화강섬장암、이장화강암、영운섬장암,기중화강섬장암、영운섬장암、이장화강암구성탑목소지구침입암적주체,암체침입만석탄세—조이첩세아목산조,우피백성계、주라계불정합복개,구역상정근동서향전포.채용LA-ICP-MS기술,측득내몽고아랍선우기탑목소지구적탑목소이장화강암화순포이영운섬장암중고석적206Pb/238U년령분별위264.2±3.3Ma화273.0±3.3Ma,저2개년령피해석위각자적침위년령,즉이자균형성우중이첩세.화강섬장암、이장화강암화영운섬장암재SiO2-K2O도해중락입개감계렬화고갑개감성계렬,A/CNK치분별위0.874~1.01、1.06~1.54화0.91~1.03;Ba、Rb、Th、K등대리자친석원소부집,Nb、Ta、P、Ti등고장강원소상대우손;희토원소총량분별개우156.99×10-6~212.87×10-6、126.92×10-6~212.98×10-6화128.13×10-6~214.5×10-6지간,균정부Eu이상;재구조배경Rb-(Yb+Nb)화Rb-(Yb+Ta)판별도해중균락입화산호화강암구.결합구역배경분석,아랍선북연재조이첩세시가능존재여호물질유관적암장활동.
Acid and intermediate-acid intrusive rocks are widely distributed in Tamusu, northern Alxa massif. These rocks are main-ly biotite granite, granodiorite, adamellite and tonalite, with the last three forming the main body of the intrusive rocks in Tamsag area. The massif, unconformably covered by Cretaceous and Jurassic strata, was intruded into Late Carboniferous-Early Permian Amushan Formation, and its regional distribution shows sub-latitudinal feature. The LA-ICP-MS zircon U-Pb ages of the mon-zonitic granite and tonalite in this region are respectively 264.2±3.3Ma and 273.0±3.3Ma. The granodiorite, monzonitic granite and tonalite are of calc-alkalic to high potassium calc-alkalic suite, characterized by A/CNK ratios of 0.874~1.01, 1.06~1.54, and 0.91~1.03, and∑REE values of 156.99×10-6~212.87×10-6, 126.92×10-6~212.98×10-6 and 128.13×10-6~214.5×10-6, respectively. These intrusive rocks show a close affinity to island-arc granites in Rb-(Yb+Nb) and Rb-(Yb+Ta) diagrams, with enrichment of Ba, Rb, Th, K and other large ion lithophile elements, and depletion of Nb, Ta, P, Ti and other high field strength elements. It is considered that the northern margin of Alxa might still have had some arc-related magmatic activities during the Permian period.