The Trans-North China Orogen (TNCO) has been recognized as a continent-continent collisional belt along which the Eastern and Western Blocks amalgamated to form the North China Craton. However, controversy has surrounded the timing and tectonic processes involved in the collision between the two blocks, ranging from the westward-directed subduction with final collision at ~2.5 Ga, through the west-dipping subduction with two collisional events at ~2.1 Ga and ~1.85 Ga, to the eastward-directed subduction with final collision at ~1.85 Ga. This project aims to present detailed lithostratigraphic, geochronological and isotopic data for the low-grade supracrustal successions in the TNCO to examine current models and to establish a reasonable scenario for the tectonic evolution of the TNCO in the Paleoproterozoic. The low-grade supracrustal successions include the Hutuo and Yejishan Groups in the middle sector of the TNCO and the Songjiashan, Lower Zhongtiao, Upper Zhongtiao, Danshanshi and Songshan Groups in the southern sector. Lithostratigraphic data indicate that the Songjiashan, Lower Zhongtiao Groups and lower parts of the Hutuo and Yejishan Groups are composed of metaclastic rocks, carbonates and metavolcanic rocks, interpreted as back-arc basin deposits, whereas the Upper Zhongtiao, Danshanshi, Songshan Groups and the upper parts of the Hutuo and Yejishan Groups consist only of metaconglomerates and metasandstones, interpreted as foreland basin deposits. To constrain the provenance and maximum depositional ages for these low-grade supracrustal successions, the LA-MC-ICP-MS technique was applied to analyze U-Pb and Hf isotopic compositions for detrital zircons from them. For the Hutuo and Yejishan Groups, we found major age peaks at ~2.5 and ~2.2 Ga and minor amounts of 2.8-2.6 Ga detrital zircons, which are consistent with ages of the lithological units in the middle sector of the TNCO. On the other hand, for the Songjiashan, Lower Zhongtiao, Upper Zhongtiao, Danshanshi and Songshan Groups, detrital zircons from them have the major age population of 2.85-1.95 Ma and the minor age population of 3.6-3.1 Ga, of which the former is comparable with ages of the lithological units in the southern sector of the TNCO and the latter was derived from the Paleoarchean and Mesoarchean crust of the Eastern Block. The maximum depositional ages of the low-grade supracrustal successions have also been well constrained in this study. For the back-arc basin deposits, their maximum depositional ages were constrained between ~2.15 and ~2.10 Ga. For the foreland basin deposits, the presence of ~1.85 Ga detrital zircons indicates that they were deposited after this time. Taken together, we present a brief scenario for the evolution of the sedimentary basins in the TNCO. At 2.15-2.10 Ga, a series of back-arc basins developed behind an “Andean-type” arc that were subsequently incorporated into the TNCO during the collision of the Eastern and Western Blocks. At ~1.85 Ga, the two blocks collided along the TNCO, resulting in the crustal thickening followed by rapid exhumation/uplift, which shifted the back-arc basins to foreland basins. Such a shift in the late Paleoproterozoic supports the model that the collision between the Eastern and Western Blocks occurred at ~1.85 Ga. / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

published_or_final_version / Earth Sciences / Master / Master of Philosophy

published_or_final_version / abstract / Earth Sciences / Master / Master of Philosophy

published_or_final_version / Earth Sciences / Master / Master of Philosophy

published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

published_or_final_version / Earth Sciences / Master / Master of Philosophy

The Archean basement rocks in Shandong Province are important components of the Eastern Block in the North China Craton, consisting predominantly of granitoid gneisses with minor mafic and felsic supracrustal rocks and charnockites. They are exposed, from west to east, in the Luxi Granite-Greenstone Terrane, Yishui Terrane and Jiaodong Terrane, of which the low-grade Luxi Granite-Greenstone Terrane has been well studied, whereas little work has been done on the medium- to high-grade Yishui and Jiaodong Terranes. Controversies have long surrounded the timing of crustal growth and tectonic setting of these two terranes. This project is designed to resolve these issues by integrating field investigations, petrography, geochronology, geochemistry and metamorphism of the Yishui and Jiaodong Terranes. New zircon U-Pb data from the major lithologies have revealed that the Jiaodong Terrane experienced multi-stage magmatism at ~2.9 Ga, ~2.7 Ga and 2.6-2.5 Ga followed by two metamorphic events at ~2.50 Ga and 1.9-1.8 Ga, whereas the Yishui Terrane underwent single magmatism at 2.57-2.53 Ga followed by a single metamorphic event at ~2.50 Ga. Zircon Hf isotopic data have revealed that the Jiaodong Terrane underwent juvenile crustal growth with significant ancient crustal material additions at 3.4-3.1 and 2.8-2.7 Ga, while the Yishui Terrane experienced juvenile crustal growth with significant addition of crustal material at 2.8-2.7 Ga. Both the Jiaodong and Yishui Terranes experienced crustal reworking with minor juvenile additions at 2.6-2.5 Ga. Whole-rock compositions and Nd isotopes from the Jiaodong granitoid gneisses suggest that their protoliths are typical Archean tonalitic-trondhjemitic-granodioritic (TTG) suite. They are high in SiO2, Al2O3, Na2O, Sr and Sr/Y ratios, but low in MgO, K2O, TiO2, Cr, Ni, Y and Mg#. They are generally enriched in light rare earth elements and large ion lithophile elements, depleted in heavy rare earth elements and high field strength elements, with slight Eu anomalies. Two groups of granitoid gneisses have been recognized: low- and high-HREE groups, of which the former was generated from partial melting of metabasaltic rocks leaving eclogite in the residue, whereas the latter was formed by partial melting of metabasaltic rocks leaving garnet-amphibolite in the residue. Whole-rock Nd isotopes reveal that the protoliths of Mesoarchean granitoid gneisses were derived mainly from juvenile sources, whereas the early Neoarchean granitoid gneisses were derived from juvenile sources with significant additions of crustal material and the late Neoarchean granitoid gneisses were mainly derived from continental crustal sources. These features indicate that the protoliths of the Jiaodong granitoid gneisses were possibly formed by partial melting of thickened lower crust related to underplating of mafic magmas. Mafic granulites (~2.50 Ga) of the Yishui Terrane show three distinct mineral assemblages corresponding to the pre-peak, peak and post-peak metamorphic stages, with P-T conditions constrained at 660-730℃/<6.6 kbar, 800-820℃ /8.0-8.5 kbar and 686-710℃/7.6-8.6 kbar, respectively, by using THERMOCALC pseudosection modeling. The results define an anticlockwise P-T path involving near-isobaric cooling following the peak metamorphism, suggesting that the ~2.50 Ga metamorphism was most likely related to the intrusion and underplating of mantle-derived magmas. Collectively, the results of this study suggest that the underplating of mantle-derived magmas was most likely related to a mantle plume, which is favored to account for the significant Neoarchean crustal growth and the large-scale metamorphism at the end of Neoarchean in Shandong Province as well as the whole Eastern Block in the North China Craton. / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

published_or_final_version / Earth Sciences / Master / Master of Philosophy

The Cenozoic Ailaoshan – Red River shear zone marks the present day western margin of the South China Block. Along this margin are well preserved late Paleoproterozoic to early Neoproterozoic sedimentary and volcanic successions. This work examines the ages and tectonic environments for the formation of the successions, as well as significance of the regional tectono-magmatic events on the formation of widespread iron oxide-copper deposits. The oldest succession is the Paleoproterozoic Dahongshan Group. A new SHRIMP UPb age of 1675 ± 8 Ma for a tuffaceous schist unit confirms its Paleoproterozoic age. Detrital zircon ages of the Dahongshan Group range between Archean to Paleoproterozoic (ca. 2780 – 1860 Ma). They include a population of ca. 2400 – 2100 Ma grains, which have no known source region on the exposed Yangtze Block. Previous geochemical studies of metavolcanic rocks from the Dahongshan Group have suggested that these rocks were erupted in an oceanic setting. However, this study shows that the metavolcanics are extremely altered and cannot be used for reliable tectonic discrimination. Based on the characteristics of sedimentary rocks in the Dahongshan Group, it is suggested that these rocks were deposited in a continental setting. Overlying the Dahongshan Group is a thick sedimentary sequence which has been variably termed the Kunyang, Dongchuan, Huili or Xide Groups. In the past, these rocks have been considered as a Mesoproterozoic rift succession. However, no precise age constraints were available for the succession. In this study, this sequence is found to contain at least two separate tectonostratigraphic units. The oldest (ca.1140 Ma) is comprised of alkaline basalt with a geochemical and isotopic character similar to that of modern intracontinental rift basalts. The presence of Cathaysia-derived sediments in this unit indicates sedimentary transportation from the southerly Cathaysia Block to the northerly Yangtze Block (in present coordinates) in South China at that time, which suggests an “impactogen” scenario. The thick sedimentary sequence of what has traditionally been defined as the Kunyang Group has been found to have significantly younger depositional age of ca.1000 – 960 Ma. The composition of sedimentary rocks and the provenance of detrital zircons from the Kunyang Group are consistent with a foreland basin setting. The depositional age of this sequence coincides with the timing of Sibao Orogeny as determined elsewhere in the South China Block. Summary Page ii Numerous iron oxide - copper (gold) deposits occur within the rocks of the Dahongshan and Kunyang Groups. Previous studies have classified these deposits into two deposit styles: the Dahongshan-type Paleoproterozoic VMS mineralisation hosted within the Dahongshan Group, and the Dongchuan-type diagenetic carbonate and shale-hosted deposits hosted within the Kunyang Group. However, both deposit types share similarities with the iron oxide – copper (gold) deposit class, such as stratabound disseminated and massive copper ores, abundance of iron oxide occurring mostly as low Ti - magnetite and haematite, and variable enrichments in Au, Ag, Co, F, Mo, P and REE. 40Ar/39Ar data from both deposit types indicate mineralisation ages of ca. 850 – 830 Ma and 780 – 740 Ma.

published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy