从海相地层磷灰石的裂变径迹探讨楚雄盆地的热史及剥蚀史

DISCUSSION ON THE THERMAL AND DENUDATIONAL HISTORY OF THE CHUXIONG BASIN ACCORDING TO THE STUDY ON THE APATITE FISSION-TRACK ANALYSIS OF MARINE-FACIES STRATA

磷灰石裂变径迹分析法是恢复沉积盆地热史的一种有效方法,以大量的磷灰石裂变径迹资料为基础,分析了楚雄盆地海相地层热历史及地层剥蚀量。本区测试的各个样品的单颗粒年龄分布特征总体上集中程度不太好,分散性较强,反映这些样品可能均未经历125℃以上的完全退火;封闭径迹长度的分布特征反映本区具有较复杂的热史,这可能与楚雄盆地构造变动强烈并伴有多期次火山活动有关。裂变径迹反映本地区3个主要不整合(D1/O2、T3/D2、K2/J2)具不同的剥蚀量,表明楚雄盆地曾有较为复杂的剥蚀史:其中云参1井3个不整合的剥蚀量分别为220m(D1/O2)、180m(T3/D2)和105m(K2/J2);云龙凹陷露头剖面3个不整合的剥蚀量为263m(D1/O2)、149m(T3/D2)和280m(K2/J2)。

The apatite track fission-track analysis is a useful method to resume the thermal history of sedimentary basin. On the basis of lots of the analytical data, this method is used to analyze the thermal history and denudational quantity of marine-facies strata of the Chuxiong Basin. The general features of the single-grain age distributions for each sample tested in the research area include the bad concentrating extent and the strong decentralism, which shows that these samples have not been experienced the complete anneal above 125℃. The length-distribution of the closed track expresses a complicate thermal history of the Chuxiong Basin. These features are genetically related to the intensive tectonic events and the multi-phase volcano activities in the evolutional history of the Chuxiong Basin. The different denudational quantities for the three main unconformities of the Chuxiong Basin that are reflected by the data of the fission-track analysis represent a sophisticate denudational history of the Chuxiong Basin. For example, the denudational quantities of the three unconformities at the well Yuncan 1 are respectively as follows: 220 m(D_1/ O_2), 180 m(T_3 / D_2)and 105 m(K_2/ J_2). At the outcrop section in the Yunlong depression are respectively as follows: 263 m(D_1/ O_2), 149 m(T_3 / D_2)and 280 m(K_2/ J_2).