摘要
海南岛前寒武纪基性岩类具有的不同的岩石地球化学特征,记录了海南岛前寒武纪大地构造环境和岩石圈的演化史。古中元古代时,琼中屯昌变基性-超基性岩,为大洋型火山岛弧低钾拉斑玄武岩,明显具有镁铁质-玄武质科马提岩特征,来源于高度亏损的地幔;与之同时代的琼西,则为一套具洋底玄武岩和岛弧拉斑玄武岩的过渡型玄武岩,是古俯冲带上部地幔楔和自消减带卷入地幔楔地壳物质所组成的混合端元部分熔融产物,具低亏损地幔特征,产生于弧后(或弧间)盆地环境;中新元古代的琼西变基性-超基性岩和古中元古代琼中屯昌变基性-超基性岩具有不同的岩石学和地球化学,为两套具不同时代、源区相异、构造环境不同的岩石类型,中新元古代的琼西变基性-超基性岩具铁镁质-超铁镁质科马提岩特征,来源于较高亏损的地幔,产于大洋板块边缘的构造环境。据此,可以推测,海南岛前寒武纪岩石圈演化至少经历了古中元古代的古板块俯冲、中新元古代的裂解二次事件,并伴随洋盆的出现。
The different characteristics of petrology and geochemistry for all kinds of basic rocks with different times record the tectonic setting and the evolutionary history of lithosphere at Precambrian era on Hainan Island. At the Paleo-Mesoproterozoic era, the meta-basic-ultrabasic rocks on eastern Hainan are oceanic low K are tholeiite with the features of mafic-basaltic komatiite evidently, originated from highly depleted mantle and are formed under the tectonic setting of volcanic are. Anyway, at the same time, in western Hainan, a kind of transitional basalt with low depleted mantle origination between MORBs and tholeiites is produced, the magma storeroom is a kind of partial melting mixture made up of mantle wedge located over old-diving depleted belt and crust material being involved into mantle wedge from depleted belt. Their tectonic setting is back-are or inter-arc spreading basin. In Meso-Neoproterozoic era, the meta-basic-ultrabasic rocks in western Hainan have different petrological and geochemical compositions at the Paleo-Mesoproterozoic era in eastern Hainan, they are different rock types with different time, different origination and different tectonic setting. The meta-basic-ultrabasic rocks in western Hainan are mafic-ultramafic komatiite originated from highly depleted mantle and being formed under the setting of the edge of oceanic ridge. Hereby. we can speculate that the evolution of lithospher during Precambrian has undergone two events of the diving of paleoplate in the Paleo-Mesoproterozoic era and the rift of continent on Meso-Neoproterozoic era at least. following the appearence of ocean basin.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2001年第4期598-608,共11页
Acta Petrologica Sinica
基金
中国科学院资源环境领域知识创新工程重要方向项目(KZCX2-113)资助.
