摘要
针对华北济阳盆地南缘、鲁西隆起北麓的博兴洼陷新生代沉积,通过矿物分离、显微鉴定、探针分析与计算,发现古近系孔店组和沙河街组第四段中存在确凿的碎屑蓝闪石、冻蓝闪石、多硅白云母等高压矿物。结合同层位碎屑重矿物组合与区域碰撞造山带物源的时比分析,说明上述高压矿物源于胶东地区的苏鲁造山带,而其源岩是否与俯冲洋壳的折返有关值得进一步研究。对碎屑蓝闪石等高压矿物物源进一步的讨论说明,它们极可能直接来源于苏鲁造山带,但不排除博兴洼陷同时期也接受了来自鲁西地区的剥露物质(含再旋回物源)。因此,鲁西隆起-苏鲁造山带晚中生代-古近纪早期具有明显的东高西低的古地理特点,而自古近纪始新世中期45Ma左右(相当于沙河街组四段顶界年龄)古地势开始逆转。换句话说,45Ma以后鲁西隆起基本阻隔了直接来自苏鲁造山带的物源。
Through detrital heavy mineral separation, microscopic identification and probe measure and compositional data analysis, some detrital high-pressure metamorphic minerals, including glaucophane, barroisite and phengite, were found from the Kongdian Formation and the No. 4 segment of Shahejie Formation, Paleogene, in the Boxing Sag located in the south margin of Jiyang basin near the north foot of Luxi Uplift. Provenance correlation analysis, with depositional records of detrital heavy mineral assemblages and petrologic tectonic attributes of regional collisional orogenic belts, shows that the detrital high-pressure minerals sourced from the Sulu orogenic belt, in which high-pressure metamorphic rocks probably resulted from return of deep subducted oceanic crust ( more research proofs needed). Further discussion on provenances of detrital high-pressure minerals in the Boxing Sag most probably directly sourced from the Sulu orogenic belt during the Early Paleogene. At the same time, exhumation materials ( including recycled deposits) of the Luxi Uplift probably become partial provenances of the Boxing Sag. Therefore, evident topography in west high to east low once occurred over the Luxi Uplift-Sulu orogenic belt during Late Mesozoic-Early Paleogene, and, however, gradually reversed since 45Ma ( corresponding to age of top layer of the No. 4 segment of Shahejie Formation). In other words, the Luxi Uplift basically obstruct provenances directly derived from the Sulu orogenic belt since 45 Ma.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2009年第12期3130-3140,共11页
Acta Petrologica Sinica
基金
国家自然科学基金项目(40672083)资助
