川西南甘洛地区中-新生代构造沉降史分析及对铅锌保存的约束

Characteristics of Meso-Cenozoic Tectonic Subsidence History and Restriction on Preservation of Zn-Pb Deposit in Ganluo,Southwest Sichuan

本文通过碎屑岩磷灰石、锆石裂变径迹和炭质泥岩镜质体反射率相结合的办法，重建了甘洛地区中新生代的构造沉降史，进而探讨了构造沉降史对铅锌保存状态的约束。研究表明：晚三叠世，甘孜-理塘洋盆和西秦岭地区洋盆的闭合作用导致研究区变为前陆环境，并开始迅速接受陆相沉积，埋深迅速增加，增幅达7.6km；晚三叠世至古近纪，甘洛地区经历过多次抬升-沉降作用，总体表现为缓慢抬升，平均抬升速率不高于32.7m／Ma；新近纪，甘洛地区快速差异隆升北部抬升速率高于南部，25.5-10.3Ma期间，平均抬升速度超过295m／Ma；在6Ma至今，平均抬升速率超过667m／Ma。快速隆升过程早于川南马边地区和临沧地区，而明显晚于攀西地区，这在一定程度上支持了青藏高原东部边界晚新生代以来幕式抬升及分步向外扩展的观点。构造沉降史结果表明成矿后的深埋藏作用对原生铅锌矿具有重要的保存作用，并影响到现今矿体的就位深度。

The tectonic subsidence history of the Ganluo is discussed and reconstructed by using apatite fission- track, zircon fission-track and vitrinite reflectance data of clastic rock, and correlative restriction on preservation of Zn-Pb deposit in Ganluo. Three stages could be defined as follows. ①During Late Triassic epoch, influenced by the subduction of the East Tethys Ocean basin, the tectonic environment of Ganluo area changed into paraforeland basin, and the buried depth stara increased rapidly, with the incremental quantity more than 7. 6km.②Early Jurassic-Paleogene, at which the tectonic regime of Ganluo area transformed and the stara uplifted discontinuously and slowly, with the average uplift rate no more than 32.7m/Ma. ③Since the beginning of Neogene epoch, the stara of Ganluo uplifted quickly, the uplift amplitude in the Northern of Ganluo is more than the Southern, the average uplift rate is more than 295 m/Ma from 25.5Ma to 10.3Ma and more than 667 m/Ma from 6Ma up to now. The rapid uplift stage of Ganluo is earlier than that of Mabian and Lincang, and significantly later than that of western Panzhihua. This uplift feature coincides with the outward propagation and growth deformation of tibetan plateau, which is is characterized by multistage coeval and disequilibrium developments. The results of tectonic subsidence history indicates the deep buried diagenesis after mineralization is significant for the preservation of Primary lead-zinc mine, and affects the current emplacement depth of ore body.