浙江江山—龙游南部地区钾玄质侵入岩的厘定及其找矿意义

江山—龙游南部地区晚中生代侵入岩分布广泛,以往被认为是钙碱性系列岩石,笔者通过野外地质、岩石学和元素地球化学研究表明,石英二长岩、二长岩、正长岩以及与之伴生的花岗岩与花岗斑岩属钾玄质系列岩石。这套岩石高碱(Na2O K2O=7.80%～10.47%)、富钾(K2O/Na2O=0.92～1.91)、贫钛(TiO2=0.2%～0.88%)、Al2O3含量较高且变化范围大(11.08%～17.77%),富集大离子亲石元素(LILE)和轻稀土元素(LREE),且Ce/Yb(27.29～85.64)、Ta/Yb(0.42～0.73)和Th/Yb(3.44～14.44)比值高,具有钾玄质系列的岩石地球化学特征。该区矿产资源较为丰富,矿床在时间与空间上多与钾玄质侵入岩密切共生,钾玄质侵入岩为成矿母岩,是重要的找矿岩石学标志。

Redefinition of shoshonitic intrusive rocks in the southern part of the Jiangshan-Longyou area, Zhejiang, and its significance for ore finding

Late Mesozoic intrusive rocks are widespread in the southern part of the Jiangshan-Longyou area, Zhejiang. They were formerly regarded as rocks of the calc-alkali series. Field geological, petrological and element geochemical studies indicate that quartz monzonite, monzonite, syenite and concomitant granite and granite porphyry belong to the shoshonitic series. This suite of rocks has higher contents of alkalis (Na2O K2O=7.80%-10.47%) and potassium (K2O/Na2O=0.92-1.91), lower titanium contents (TiO2=0.2%-0.88%) and a higher content and wide range of Al2O3 (11.08%-17.77%) and is enriched in large ion lithophile elements(LILE) and light rare earth element(LREE), with high ratios of Ce/Yb(27.29-85.64), Ta/Yb(0.42-0.73) and Th/Yb(3.44-14.44), showing the geochemical characteristics of shoshonitic series rocks. The area is endowed with rich mineral resources, and most ore deposits are intimately associated with shoshonitic intrusive rocks in terms of both time and space. The shoshonitic intrusive rocks are parent rocks of ores, which are an important petrological indicator for ore finding.