【作者】 孟恩；

【导师】 许文良；

【作者基本信息】 吉林大学 ， 矿物学、岩石学、矿床学， 2011， 博士

【摘要】 本文以黑龙江省东部晚古生代早期地层底部砂岩和晚古生代-早中生代火山岩为研究对象,通过对砂岩中碎屑锆石LA-ICP-MS U-Pb年代学研究和物源分析,确定了晚古生代早期地层的沉积下限,并讨论了松嫩—张广才岭地块与佳木斯地块之间的拼贴时间；通过对火山岩中锆石的LA-ICP-MS U-Pb年代学和火山岩的主量、痕量元素及Sr-Nd同位素以及锆石Hf同位素的地球化学研究,确定了火山岩的形成时代,讨论了研究区不同时代火山岩的岩石组合和岩浆源区性质及其形成的构造背景。最终结合区域地质资料,探讨了研究区晚古生代-早中生代区域构造演化历史。研究区晚古生代早期地层砂岩碎屑锆石U-Pb定年结果显示：1)小兴安岭滨东早泥盆世黑龙宫组(D1h1)和汤原早泥盆世宝泉组(Dlb)下部石英砂岩中碎屑锆石分别具有：2503、1833、903-802、551-403 Ma和2508、898-749、495-413Ma年龄数据；最年轻的碎屑锆石表明黑龙宫组和宝泉组的沉积作用分别发生在403 Ma和413 Ma之后；大量-2.5Ga、-1.8Ga、903-800Ma古老锆石的存在,暗示在早泥盆世期间,松嫩—张广才岭地块(可能包括额尔古纳地块和兴安地块)之上存在有前寒武纪古老陆壳残片；而黑龙宫组(D1h1)和宝泉组(Dlb)中大量489-551 Ma碎屑锆石的存在——这些年龄的锆石主要分布在佳木斯地块之上,暗示松嫩—张广才岭地块和佳木斯地块的碰撞拼贴在403-413 Ma之前已经完成(应为加里东晚期)。2)佳木斯地块东缘早-中泥盆世黑台组(D1-2ht)砂岩中碎屑锆石具有569、542、509和484Ma年龄数据,这表明其沉积下限为484Ma之后,沉积物源只是佳木斯地块本身。研究区火山岩锆石U-Pb定年结果表明,该区晚古生代-早中生代火山作用可分为四期：中-晚泥盆世(-386Ma)、早二叠世(-291Ma)、中二叠世(-268Ma)和晚三叠世(201-217Ma)。中-晚泥盆世佳木斯地块东缘发育双峰式火山岩,暗示被动陆缘环境,而同期小兴安岭地区发育“A”型流纹岩,表明陆内伸展环境；早二叠世佳木斯地块东缘发育钙碱性火山岩组合,暗示活动陆缘背景,而同期张广才岭地区发育典型双峰式火山岩组合,揭示陆内伸展环境：中二叠世佳木斯地块东南缘发育同碰撞型流纹岩类,表明佳木斯地块与兴凯地块此时已经碰撞拼贴；晚三叠世南北向带状展布的“A”型流纹岩的存在,揭示陆内伸展环境,同时表明古亚洲洋构造域与环太平洋构造域的转变应发生于晚三叠世之后。更多还原

【Abstract】 This thesis studies the provenance and maximum age of deposition of the Late Paleozoic sedimentary strata and the formation time of the Late Paleozoic-Early Mesozoic volcanic rocks in eastern Heilongjiang Province by using LA-ICP-MS zircon U-Pb chronology. Besides, we discuss the nature of magma sources, and their tectonic setting based on major-and trace-elements, and Sr-Nd isotope as well as zircon Hf isotope for these volcanic rocks. These chronological and geochemical data, together with regional tectonic analysis, provide constraints on the Late Paleozoic-Early Mesozoic tectonic evolution in eastern Heilongjiang Province. Main achievements are as follows:1. Maximum age of deposition of the Late Paleozoic basins in eastern Heilongjiang ProvinceThe dating results of detrital zircons from quartz sandstones of the Early Devoniar Heilonggong (D1hl) (in eastern Harbin), the Early Devonian Baoquan (D1b) (in the Lesse: Xing’an Range), and the Early-middle Devonian Heitai formations (D1-2ht) (in eastern margir of the Jiamusi Massif) as well as the formation times of the volcanic rocks within the overlying stratas, reveal that:(1) rocks from the D1hl Formation is deposited after 403 Ma; (2) the Dih and Dib formations are deposited between 413～386 Ma, and 484～390 Ma, respectively.2. Remnants of ancient crystalline basementDetrital zircon dating results from the Dihl and D1b formations reveal that they wer sourced from regions with rocks as old as～2500,～1833, and 903～800 Ma in addition to th Phanerozoic material. Taking into account the paleomagnetic data, the timing of the final closure of the Paleo-Asian ocean and the researches on the Phanerozoic granites within the CAOB, it appears that these Archean/Proterozoic zircons were derived from a local source close to these Late Paleozoic basins, i.e., several ancient Precambrian crustal remnants exist within the Xing’an, Erguna, and Songnen-Zhangguangcai Range massifs in the Paleozoic.3. Timing of the amalgamation of the Songnen-Zhangguangcai Range and Jiamisi massifsThe dating results show that the D1hl and D1b formations of the Songnen-Zhangguangcai Range Massif contain numerous detrital zircons with ages of 489～551 Ma, similar to the age features of the Mashan Complex, Early Paleozoic gneissic granitoids, and the detrital zircons of the D1-2ht Formation in the Jiamusi Massif. This finding suggest that the collision between the Songnen-Zhangguangcai Range and Jiamisi massifs most possibly took place prior to the deposition of the D1hl and D1b formations, i.e., before 403～413 Ma. Combination with the existence of the north-south-trending Caledonian I-type granitoid belt (445 Ma), we propose that the amalgamation of the Jiamusi and Songnen-Zhangguangcai Range massifs probably occurred between the Late Ordovician and early stage of the Early Devonian (413～445 Ma).4. Spatial and Temporal Features of the Late Paleozoic-Early Mesozoic Volcanisms in eastern Heilongjiang ProvinceWe undertook LA-ICP-MS zircon U-Pb dating for the Late Paleozoic-Early Mesozoic volcanic rocks in eastern Heilongjiang Province. Zircons from these volcanic rocks are euhedral-subhedral in shape and display striped absorption and fine-scale oscillatory growth zoning as well as their high Th/U ratios, implying a magmatic origin. The dating results show that the Late Paleozoic-Early Mesozoic volcanic rocks in the study area can be divided into four stages, i.e., the Middle-late Devonian (-386 Ma), Early Permian (～291 Ma), Middle Permian (～268 Ma) and Late Triassic volcanisms (201～217 Ma). Moreover, the two former volcanisms widespreadly exist in the eastern margin of the Jiamusi Massif, Lesser’Xingan and Zhangguangcai ranges; the Middle Permian volcanisms mainly occur in southeastern margin of the Jiamusi Massif; whereas the Late Triassic volcanisms chiefly outcropped in western margin of the Khanka Massif. 5. Determinations of the passive continental-margin setting in eastern margin of the Jiamusi Massif and an intra-continental extensional environment in the Lesser Xing’an Rang in Middle-late Devonian.The Middle-late Devonian volcanic rocks in eastern margin of the Jiamusi Massif are composed mainly of major rhyolite and minor basalt, displaying the features of the typical bimodal volcanism. Combined with the coeval sedimentary characteristics, we propose that there exist a passive continental-margin setting in eastern margin of the Jiamusi Massif in Middle-late Devonian. Furthermore, the coeval volcanic rocks occurred in the Lesser Xing’an Range have the features of A-type rhyolite, indicating an intra-continental extensional environment. The above findings are also consistent with the extensional environment existed after the amalgamation of the Songnen-Zhangguangcai Range and Jiamisi massifs in the Late Caledonian.6. Determinations of the active continental-margin setting in eastern margin of the Jiamusi Massif and an extensional environment in the Zhangguangcai Range in Early Permian.The Early Permian volcanic rocks in eastern margin of the Jiamusi Massif are composed mainly of basalt, basaltic-andesite, and minor dacite. They belong to the subalkaline series, and display a calc-alkaline evolutionary trend, indicating that an active continental-margin setting could exist in the eastern margin of the Jiamusi Massif in the Early Permian. Besides, there exist voluminously coeval basalt, andesite-basalt and rhyolite in the Zhangguangcai Range. The geochemical data show that they are typical of bimodal volcanism. Together with the coeval A-type granites, the early Permian bimodal volcanic rocks in the study area indicate an extensional environment in the Zhangguangcai Range. Combined with the regional geological data and an active continental setting in eastern margin of the Jiamusi Massif, we propose that the bimodal volcanism in the Zhangguangcai Range could form in an extensional tectonic setting, similar to a back-arc basin, and its formation could be related to subduction of the Paleo-Asian oceanic plate beneath the Songnen-Zhangguangcai Range and Jimusi massifs.7. Timing of the amalgamation of the Jiamisi and Khanka massifs The Middle Permian volcanic rocks in eastern and southeastern margin of the Jiamusi Massif consist mainly of rhyolite and minor dacite. They are characterized by high SiO2, low MgO, enrichment in K2O, Rb, Th and U, and depletion in Eu, Sr, P and Ti, implying a crust-derived origin and similar to the syn-collisional rhyolites. Therefore, it is proposed that the Middle Permian volcanic rocks could have formed under the collision of the Jiamusi and Khanka massifs.8. Determinations of the intra-continental extensional environment in western margin of the Khanka massif in Late Triassic.The Late Triassic volcanic rocks in western margin of the Khanka Massif consist mainly of rhyolite and minor dacite. These geochemical features are similar to those characteristics of A-type rhyolite, suggesting an extentional setting. Combined with the regional geological data, the Late Triassic volcanic rocks could form in an inter-continental extensional environment related to the final closure of the Paleo-Asiatic ocean and the collision of the NCC and Jiamusi-Khanka Massif in the late Paleozoic-Early Triassic.更多还原