CAJ | 학술논문

对浙西新路火山盆地发育的辉绿岩进行了激光显微探针40Ar-39Ar 定年和系统的岩石地球化学特征研究.研究表明,新路盆地辉绿岩成岩时代为(93±3) Ma,属晚白垩世产物;岩石中辉石有单斜辉石和斜方辉石两个种属,斜长石为拉长石; SiO2含量介于44.00%~50.09%之间,具有富碱(平均为5.15%)、高钾(K2O/Na2O平均为1.08)、低TiO2含量(平均为1.15%)等特征;岩石具有原生岩浆特点,显示典型的钾玄岩特征.钾玄岩富集 LREE、大离子亲石元素和强不相容元素,无 Eu 亏损;锶初始值(Isr)介于0.70707~0.70870之间,(143Nd/144Nd)i介于0.512338~0.512407之间;Δ7/4Pb为6.0~9.2、Δ8/4Pb为48.5~68.0、DSr为70.73~87.04,均表现出富集地幔特征.认为新路盆地钾玄岩的厘定对该区域岩石圈与构造岩浆演化的深入研究具有重要意义;钾玄岩形成与造山带后碰撞期的热点活动相关;钾玄岩侵位年龄基本限定了新路地区岩石圈大规模减薄的时限;推测热点活动导致岩石圈减薄的动力学演化过程及其壳幔作用源区可能对火山岩型铀成矿起着重要的制约作用.
대절서신로화산분지발육적휘록암진행료격광현미탐침40Ar-39Ar 정년화계통적암석지구화학특정연구.연구표명,신로분지휘록암성암시대위(93±3) Ma,속만백성세산물;암석중휘석유단사휘석화사방휘석량개충속,사장석위랍장석; SiO2함량개우44.00%~50.09%지간,구유부감(평균위5.15%)、고갑(K2O/Na2O평균위1.08)、저TiO2함량(평균위1.15%)등특정;암석구유원생암장특점,현시전형적갑현암특정.갑현암부집 LREE、대리자친석원소화강불상용원소,무 Eu 우손;송초시치(Isr)개우0.70707~0.70870지간,(143Nd/144Nd)i개우0.512338~0.512407지간;Δ7/4Pb위6.0~9.2、Δ8/4Pb위48.5~68.0、DSr위70.73~87.04,균표현출부집지만특정.인위신로분지갑현암적전정대해구역암석권여구조암장연화적심입연구구유중요의의;갑현암형성여조산대후팽당기적열점활동상관;갑현암침위년령기본한정료신로지구암석권대규모감박적시한;추측열점활동도치암석권감박적동역학연화과정급기각만작용원구가능대화산암형유성광기착중요적제약작용.
@@@@The laser microprobe 40Ar-39Ar dating and detailed study of petrogeochemical characteristics of the diabase developed in Xinlu volcanic basin of western Zhejiang were carried out. The results indicate that the diabase was formed in Late Cretaceous with an age of (93±3) Ma. The diabase contains two kinds of pyroxenes (clinopyroxene and orthopyroxene), the plagioclase is labradorite, and the content of SiO2 is between 44.00%and 50.09%, characterized by rich alkali, (5.15% on average), high K (K2O/Na2O 1.08), and low Ti (TiO2 1.15%). Its petrological and geochemical characteristics show typical shoshonite. The shoshonite is enriched in LREE, LILE and incompatible elements, without Eu depletion, (87Sr/86Sr)i and (143Nd/144Nd)i are in the ranges of 0.70707 to 0.70870 and 0.512338 to 0.512407 respectively, Δ7/4Pb=6.0~9.2, Δ8/4Pb=48.5~68.0, and DSr=70.73~87.04, showing relatively enriched mantle signatures. It is concluded that the shoshonite in Xinlu basin is the product of lithospheric thinning combined with hotspot activity in the post-collision period of the orogenic zone. The age of shoshonite fundamentally restricts the time limit of the large-scale lithospheric thinning in Xinlu area, and suggests that dynamic processes of lithospheric thinning was affected by hotspot and the sources of crust-mantle interaction migtht have played an important role in controlling volcanics-type uranium mineralization.