摘要
以往主要依据地球化学证据推断东南沿海中生代存在地幔富集作用 ,但缺乏可靠的地质学证据。运用全岩 +单矿物 (斜长石和辉石 )Rb Sr等时线法 ,测得梅州辉长岩 橄榄岩岩体中辉长岩的年龄为 178.71±3 .9Ma ,( 87Sr 86 Sr) i 值为 0 .70 5 5 5 8,εSr(t)值为 17.87～ 18.16;3个辉长岩样品的 ( 1 43Nd 1 44 Nd) i 值为 0 .5 12 641～0 .5 12 665 ,εNd(t)值为 0 .4 3～ 0 .95 ,表明其源区为类似原始地幔的弱富集型地幔 ,从而首次得到了中生代存在富集地幔的地质学证据。中生代基性岩类地球化学性质的变化表明 ,大约在中侏罗世早期 ( 164～ 165Ma) 。
The metasomatic enrichments of Mesozoic mantles in the coastal Southeast China were inferred mainly by geochemical deduction, but reliable geologic evidence is lacking. According to the whole rock and single mineral (plagioclase+pyroxene) Rb Sr isochron dating, the gabbros of Meizhou gabbro peridotite (containing amphiboles and phlogopites) intrusions have an age of 178.71±3.9 Ma, ( 87 Sr/ 86 Sr) i ratio of 0.705 558, and average ε Nd ( t ) values of 0.7, demonstrating that they derived from a slightly enriched mantle similar to the primitive mantle. This is the first geologic evidence for metasomatic enrichment of Mesozoic mantles. The geochemical variations of Mesozoic mafic rocks indicated that the coastal Southeast China has transferred into the Pacific tectonic domain since about early Middle Jurassic (164～165 Ma).
出处
《矿物岩石地球化学通报》
CAS
CSCD
2001年第3期172-175,共4页
Bulletin of Mineralogy, Petrology and Geochemistry
基金
国家自然科学基金项目 ( 40 0 0 2 0 0 5 )
中国地质调查局地调项目 ( 2 0 0 1130 0 0 0 5 3)联合资助
关键词
地质学证据
中生代地幔富集作用
早侏罗世基性超基性岩体
广东梅州
geologic evidence
Mesozoic mantle enrichment
Early Jurassic mafic ultramafic intrusion
Meizhou of Guangdong Province
