The oldest rocks provide direct constraints on the nature of the first crust on Earth and the earliest magmatic process, which is significant for understanding the physical and chemical properties of our planet's early stage. On the modern Earth, Hadean to Eoarchean crustal rocks have been identified in less than ten areas worldwide. Due to relatively poor preservation of early Archean rocks, major controversies exist on the tectonic mechanisms responsible for the formation of the continent during the early Earth. Therefore, identification of new Eoarchean or even Hadean crustal exposures would provide key information for understanding the formation and evolution of early continental crust and its geodynamic driver in the early Earth. Here, we report the new identification of Eoarchean trondhjemitic gneisses in the Muzidian Gneiss Complex (MGC) in the northern margin of Yangtze Craton. Zircon SHRIMP U-Pb ages of 3855 +/- 7 Ma and 3851 +/- 6 Ma suggest this trondhjemite unit in the MGC is the oldest known igneous rock in Eurasia. Zircon Hf isotopic compositions indicate that the MGC gneisses were formed from reworking of pre-existing Hadean crust older than 4.1 Ga. These newly recognized rocks in the MGC mark an important, Hadean crust derived, ancient gneiss complex, which is isotopically comparable to the Acasta Gneiss Complex in the currently established global Eoarchean geological record. Our findings indicate that at least some of the earliest crustal rocks might have originated from an early-differentiated, incompatible elementenriched protocrust in the Hadean.

Current consensus holds that lunar magmas form in mantle reservoirs produced by crystallization of the Lunar Magma Ocean (LMO), which also explains formation of the primary lunar crust. Here we present Pb isotope data from two groups of impact melt fragments in the Chang’e-6 soil sample with ages of 4245 ± 4 Ma and 3876 ± 4 Ma, interpreted as impact remelting of the crust. The fragments show radiogenic initial Pb isotopes and a moderate crustal μ (²³⁸U/²⁰⁴Pb) of 683 ± 140, which cannot be explained by the evolution involving LMO crystallization and do not support a primary origin for this crust. Instead, the data require post-LMO remelting of the crust and underlying mantle, probably triggered by the South Pole–Aitken (SPA) impact. Crystallization of the SPA impact melt produced localized secondary reservoirs with variable μ-values, including secondary crust subsequently sampled by the two fragment groups from Chang’e-6 sample. Pb isotopes from Chang’e-6 impact melt fragments show that the SPA-region crust is not purely a primary product of lunar magma ocean crystallization, but formed through post-LMO remelting and differentiation of crust and upper mantle.

Atom Probe Tomography (APT) enables high-resolution elemental analysis at the nanoscale, making it an essential tool in Earth sciences. Recent advancements have focused on trace element distribution, mineral element migration, and water content analysis at the nanoscale. In this study, we present APT-based techniques for analyzing trace element enrichment in arsenian pyrite, water content and occurrence in glass, and isotope analysis with nanometer resolution.Arsenian Pyrite in Carlin-type Gold Deposits:We investigated arsenian pyrite with banded structures from a Carlin-type gold deposit using APT combined with SEM-EBSD, EPMA, LA-ICP-MS, and STEM. This multi-method approach revealed the structural and compositional characteristics of pyrite at micro- to nanoscale resolutions. Our findings show that Au, As, and Cu are hosted in pyrite in a substitutional form, while Sb, Pb, Hg, and Tl are concentrated as non-structural impurities in lattice defects. The accumulation of trace elements is coupled with the formation of lattice defects during pyrite’s growth, which transitions from a layered to an island-like growth pattern and back to a layered structure. The study also highlights the crucial role of As in promoting metal enrichment, and surface adsorption of Au as a key mechanism for gold mineralization.Water Content and occurrence in Glass:We applied APT in combination with NanoSIMS to study the nanoscale water content, occurrence, and distribution in water-bearing glass samples. The detection limit was achieved down to 0.02 at% for hydroxyl water. We identified nano-sized hydroxyl-water inclusions in glass, with higher hydroxyl water content in these inclusions correlating with increased water content in the surrounding glass. This demonstrates APT’s ability to analyze nanoscale water content and to distinguish hydroxyl water and nano-sized inclusions in mineral samples.Silicon Isotope Analysis:APT was also used to analyze silicon samples, including both standard pure silicon and silicon with different isotope ratios. After background correction and mass ranging, we achieved precise nanoscale isotopic ratio analysis. Studies on AVO28 and UHP silicon samples revealed homogeneous distribution of isotopes at the nanoscale without impurities. Our results matched those obtained by MC-ICP-MS and SIMS, demonstrating APT's potential to provide high spatial resolution isotopic analysis for geological sample analysis.In conclusion, APT offers a powerful tool for exploring nanoscale trace elements, water content, and isotope ratios in geological samples, advancing our understanding of Earth and planetary materials.

Jingshan Group metasedimentary rocks are widespread east of the Wulian-Yantai fault. Only a few studies focus on the provenance, depositional age, metamorphic timing and tectonic affinity of these rocks. Two Jingshan Group metasedimentary rocks and one associated gneissic trondhjemite were selected for SHRIMP U-Pb dating. Zircons from the metasedimentary rock near Xujiadian town show a major U-Pb age cluster at 2.55-2.45 Ga, with minor clusters at 2.2-2.0 Ga and ~2.72 Ga and a few >3.0 Ga. The sample was metamorphosed at ~1.86 Ga. Detrital zircon cores from the other metasedimentary rock collected at Huxi village likely crystallized at ~2.56 Ga, whereas the rims yield two metamorphic ages of 2.47 Ga and 231 Ma. A gneissic trondhjemite that may have intruded the second metasedimentary rock was emplaced at 2.51 Ga and metamorphosed at 2.47 Ga. According to these results, the depositional ages of the metasedimentary rocks from Xujiadian town and Huxi village can be constrained to 2.1-1.86 Ga and 2.56-2.47 Ga (possibly 2.56-2.51 Ga), respectively. Our studies indicate that small volumes of late Archean to early Paleoproterozoic (~2.5 Ga) supracrustal rocks can be distinguished from the metasedimentary rocks described as belonging to the mid-late Paleoproterozoic Jingshan Group. The two metasedimentary rocks presented in this study were derived from the Jiaobei terrane. Combining our results with published data, basement rocks located east of the Wulian-Yantai fault have a Jiaobei terrane affinity, implying that the suture zone between the Jiaobei terrane and the Sulu orogeny lies east of the Wulian-Yantai fault and is probably represented by the Muping-Jimo fault. The weighted mean age of 230.8 ± 5.5 Ma obtained from zircon metamorphic rims of biotite-muscovite schist (JS02) reported here provides robust evidence that the basement rocks of the Jiaobei terrane were involved in the Triassic subduction of the Yangtze Craton.

Volcanism on the Moon has produced surface basalt deposits, which record lunar interior processes. The Chang’e-6 mission retrieved samples from the South Pole-Aitken basin (SPA) on the Moon’s far side. We analyze basalt fragments collected by Chang’e-6, finding their composition resembles low-Ti basalts previously sampled by the Apollo missions. U-Pb dating indicates a basalt age of 2823.0 ± 5.9 Ma and a source 238 U/ 204 Pb ratio (μ-value) of 480 ± 56. This high μ-value indicates that the source contained materials that formed during late stages of lunar magma ocean (LMO) crystallization. The results are consistent with the LMO model, but the Chang’e-6 basalt deviates from the trend in Apollo mission samples of younger basalts having higher μ-values. We suggest this indicates post-LMO modification of the mantle by the SPA impact.

The exposure of the Archean-Paleoproterozoic basement in the Yangtze Block is very limited, which constrains the understanding of its Early Precambrian geological evolution. In this study, U-Pb ages, Hf-O isotopes and trace elements of detrital zircon from the metasedimentary rocks of the Dahongshan and Kunyang groups in the Cuoke area are reported. Zircon from Dahongshan Group Aeld a spectrum age ranging from 3092 to 1786Ma, and the youngest detrital zircon has an age of 1786Ma, limiting the maximum depositional age of the Dahongshan Group to the Late Paleoproterozoic. The age distribution of the concordant zircon in the Kunyang Group is between 2874Ma and 1031 Ma, and the youngest age of detrital zircon is 1031 Ma, indicating that the maximum depositional age of the Kunyang Group is the late Middle Proterozoic. Except for a small amount of younger zircon (<1.75Ga), the Kunyang and Dahongshan groups have similar age distribution characteristics, with two main age peaks of 2.0-1.85Ga and 2.4- 2. 2Ga. Although the age peaks observed in the Paleoproterozoic detrital zircon are consistent with the Paleoproterozoic magmatic rocks reported in the Cuoke area, only a small portion of the detrital zircon have Hf-O isotopic characteristics similar to the Paleoproterozoic magmatic rocks in the Cuoke area, and most of the detrital zircon have Hf-O isotopic compositions similar to those of the Paleoproterozoic metasedimentary rocks of the Rae Craton in Canada, which suggests that a small portion of the Paleoproterozoic components originated from the identified Paleoproterozoic magmatic rocks in the Cuoke area, and most of them may be derived from a source region which is similar to the Paleoproterozoic magmatic rocks developed in the Rae Craton. The 1.9-1.03 Ga detrital zircon in the Dahbagslan and Kamyang groups may be derived from the LatoPaleoproteinate Mesapraticamagmation roski distributedin the southwestern margin of the Yangtze Block. Combined with previous studies, we suggest that the Paleoproterozoic tectonic evolution of the Cuoke area in China and Phan Si Pan belt in northern Vietnam is similar to that of the Rae Craton in Canada, supporting the proposal that the southwestern margin of the Yangtze Block was involved in the Arrowsmith orogeny, and then underwent the assembly of the Columbia supercontinent together with the Rae Craton.

Pyrite is an important Co-bearing mineral. The Co content of Co-enriched pyrite in natural cobalt deposits can reach 10%similar to 20%, which is significantly higher than the solid solubility limit of Co in pyrite obtained from experimental and theoretical methods. At present, the mechanism of the dissolution of supersaturated Co in pyrite and whether the Co-supersaturated pyrite underwent cattierite exsolution are not clear. In order to solve the above issues, Co-enriched pyrite from Dahenglu deposit in Jilin Province was selected in this study. EDS elemental mapping and EPMA results show that Co distribution in Dahenglu Co-enriched pyrite is heterogeneous and irregular, and the Co contents of single pyrite grain are variable (4.31%similar to 9.74% for Py108, 4.54%similar to 8.83% for Py110). The heterogeneity of Co distribution is probably related to the growth process and crystallization environment of pyrite. The results of TEM and APT show that Co distribution in Dahenglu Co-enriched pyrite is homogeneous at the nanoscale, and no Co-enriched inclusions and cattierite exsolution are identified, implying that Co is incorporated into Co-enriched pyrite by isomorphic substitution for Fe. According to the above results, we propose that the incorporation of supersaturated Co in Dahenglu Co-enriched pyrite is probably related to the crystallite size effect, and the metastable state of Co-supersaturated FeS2-CoS2 solid solution can remain unchanged over a long period of time.

We carried out a petrological, mineralogical, and geochemical study of fragmental and regolith breccia clasts separated from two Chang'e-5 (CE-5) soil samples, CE5C0000YJYX03501GP and CE5C0400, which provide an opportunity to investigate the compositional change of regolith at the landing site through time. Fragmental breccia CE-5-B3 contains a diverse range of basaltic clasts and basaltic mineral fragments, and some rare Mg-suite-like minerals. Regolith breccias CE-5-B006, CE-5-B007, CE-5-B010-08, CE-5-B010-09, CE-5-B011-07, and CE-5-B016-03 contain mare basaltic fragments, mare vitrophyric clasts, rare Mg-rich fragments possibly derived from the Mg-suite rocks, and impact-derived glass spherules. Pb-isotope data obtained for baddeleyite grains found both inside some of the basaltic clasts identified in breccia fragments and in the breccia matrices yield Pb/Pb dates similar to the 2 Ga crystallization age of the CE-5 basalt fragments, extracted directly from the soil sample. Seventy-four Pb isotope analyses of Ca-phosphate grains also indicate that the majority of these grains have Pb/Pb dates of 2 Ga, suggesting that they originate from the CE-5 basalts. In addition, a Pb-Pb isochron drawn through analyses of four Ca-phosphates in breccia CE5-B006 yielded an intercept corresponding to a date of 3871 +/- 46 Ma, which is the best possible estimate of the formation age of these four grains. Electron probe microanalysis shows that the breccias contain components similar to CE-5 mare basalt fragments extracted directly from the soil sample, implying that the fragmental and regolith breccia fragments are mostly composed of material sourced from the underlying basalts. The general absence of impact melt breccia clasts, along with the general lack of Fe-Ni metal and absence of added meteoritic debris all suggest that the regolith at the CE-5 landing site is immature and dominated by material mixed together by small local impact cratering events. Trace element analyses show that the glass beads in the regolith breccias have a Th abundance of 4.06-5.28 mu g g-1. This is similar to the Th content of the regolith above the Em4 unit at the landing site as measured from orbit, as well as the estimated bulk Th content of CE-5 basalts, suggesting that Th of the local regolith is predominantly sourced from the underlying mare basalts, without significant Th addition from Th-rich exotic clasts sourced from evolved lunar lithologies.

陆丰13东洼是珠江口盆地油气勘探的重点区域.结合区域构造背景,在精细解释高品质三维地震资料的基础上,对陆丰13东洼的洼陷结构和构造特征进行综合分析,并运用平衡剖面技术对洼陷的构造演化进行了恢复与研究,探讨了构造演化对圈闭形成与成藏的影响.研究结果表明:①陆丰13东洼新生代构造演化可划分为早—中始新世断陷、晚始新世断坳转换、渐新世—第四纪区域热沉降坳陷等3个阶段,其中断陷阶段具有完整的断陷旋回,根据断陷活动的强弱可进一步划分为断陷初始期、断陷高峰期、断陷萎缩期,断陷初始期和断陷萎缩期储层较为发育,断陷高峰期烃源岩较为发育.②在多期次构造活动的影响下,陆丰13东洼新生代形成了多种类型的圈闭,包括披覆背斜圈闭、断背斜圈闭、断块圈闭、断鼻圈闭、构造-地层圈闭(削截、超覆)、构造-岩性圈闭.众多的圈闭类型表明研究区油气勘探潜力巨大,特别是断陷阶段与断坳转换阶段沉积的文昌组和恩平组均发育大量各类型圈闭,且邻近优质烃源岩,成藏条件优越,是陆丰13东洼油气勘探的重点层系;平面上,南部缓坡带发育圈闭类型及数量最多,其次是中央隆起带与低凸起,均是研究区油气勘探的重要区带.

珠江口盆地白云凹陷裂陷期发育文昌组与恩平组2套烃源岩,湖盆沉积演化控制烃源岩的形成.通过三维地震资料及深部钻井分析,认为白云主洼裂陷期发育轴向辫状河三角洲体系、断控扇三角洲体系、北缘缓坡带辫状河三角洲体系以及盆内滨浅湖—中深湖体系.裂陷早期,发育多组NE向断阶且呈现多隆洼的地貌特征,物源主要从东西轴向进入凹陷内,形成多点供源水系,发育多洼成烃;裂陷中期,由于拆离断层的伸展作用,湖盆扩张,北部番禺低隆起被强烈抬升,形成缓坡大规模的三角洲体系及大型湖盆;裂陷晚期,湖盆以拗陷作用为主,受华南物源及由南往北的海侵影响,发育煤型及海侵烃源岩.通过沉积相、地球化学指标可将白云凹陷烃源岩划分为3种类型:文昌组中深湖相Ⅰ—Ⅱ1型烃源岩、文昌组浅湖相Ⅱ2型烃源岩以及恩平组浅湖相Ⅱ2—Ⅲ型烃源岩,不同类型烃源岩生烃潜力有差异,以文昌组中深湖相最优.元素地球化学指标揭示湖盆成烃环境整体表现为淡水—微咸水、还原—强还原的水体环境,而古生物揭示湖盆生油母质为湖相浮游藻类及陆源植物,优质烃源岩有机质来源以浮游藻类为主.总之,白云凹陷拆离断裂活动及沉积体系控制了烃源岩的发育厚度和规模,优质的水体环境控制了优质烃源岩的形成.因此,白云凹陷烃源岩具有厚度大、分布范围广的地质条件,具有大的资源和勘探潜力.

Anshan is located in the northeastern North China Craton and has a long-term geological history back to 3.8 Ga. Four complexes with ages of 3.8-3.1 Ga have been identified previously, namely the Baijiafen, Dongshan, Shengousi and Guodishan complexes. Being similar to the neighbouring Beijiafen Complex, the newly-discovered Hujiamiao Complex extends in a northwest-southeast direction and shows tectonic contacts on one side with the Chengtaigou granite and on the other with the Chengtaigou supracrustal rocks. In the Hujiamiao Complex, trondhjemitic rocks of 3789 Ma, 3786 Ma, 3698 Ma, 3617 Ma, 3566 Ma, 3504 Ma and 3106 Ma have been identified. More work is required to establish if a gabbro also has a formation age of 3.8 Ga. The trondhjemitic rocks show similar compositional features in being high in SiO2 (72.37-76.71 %) and Na2O (5.00-6.47 %) and low in K2O (0.60-1.95 %), FREE contents (32.83-91.83 ppm) and (La/Yb)n ratios (11.09-48.64). They have whole-rock epsilon Nd(t) values of 0.35-4.43, tDM(Nd) of 3.74-3.46 Ga and tCC(Nd) ages of 3.74-3.43 Ga, and in situ magmatic zircon epsilon Hf(t) values of -12.3 to 1.56, tDM(Hf) ages of 4.2 to 3.5 Ga and tCC(Hf) ages of 4.6 to 3.7 Ga. Combined with previous work, it is concluded that all the Anshan area 3.8-3.3 Ga complexes are the relics of a larger complex which was once more widely distributed in the Anshan area. The trondhjemitic rather than tonalitic character of the Anshan Eoarchean rocks shows diversity in the formation and evolution of the earliest continental crust with a range of T/P for crustal anatexis.

The Fenzishan and Jingshan groups in the Jiaobei Terrane are important components of the Paleoproterozoic Jiao-Liao-Ji belt. The study of the age histograms and Hf isotopic characteristics of detrital zircons from these two groups will provide great help for understanding of the tectonic evolution of the Jiao-Liao-Ji belt. The U-Pb dating on the detrital zircons and their metamorphic rims in the Xiaosong, Zhanggezhuang and Jutun formations of the Fenzishan Group obtained concordant zircon ages within the range of 1842 similar to 3663Ma. Thirteen zircon rims have ages of 1842 similar to 1877Ma, indicating that the Fenzishan Group underwent a Late Paleoproterozoic metamorphism, which is consistent with that of the Jingshan Group. The detrital zircons in all the three formations have the ages of 2. 2 similar to 2. 1Ga. Combined with early studies, the main body of the Fenzishan Group should be deposited at 2. 1 similar to 1. 9Ga. The age peaks and epsilon(Hf) ( t) values of detrital zircons from the Fenzishan Group are basically consistent with the Early Precambrian magmatic rocks in the Jiaobei Terrane, indicating that its detrital materials are most likely to be originated from this terrain. In addition, about 17% of similar to 2. 5 Ga detrital zircons from the Jutun Formation samples have obviously low epsilon(Hf) (t) values (- 5. 79 similar to - 2. 44), which may be formed by partial melting of early magmatic rocks, suggesting that not only large-scale primary crustal growth but also early crustal remelting occurred in the Late Neoarchean in the Jiaobei Terrane. The age distributions of detrital zircons from the Fenzishan and Jingshan groups are basically identical to each other, and both of them contain typical age peaks of Jiaobei Terrane (similar to 2. 7Ga and similar to 2. 9Ga). In combination with their spatial distribution relationships, the identical metamorphic ages and clockwise P-T-t trajectories, it can be concluded that both the Fenzishan and Jingshan groups were probably deposited on the same side of the Jiaobei Terrane and subducted southeastward with this terrane afterwards.

Glacial diamictite may provide important information on paleoenvironment and average composition of the upper continental crust (UCC). In this study, we report sedimentary facies, petrological and geochemical characteristics of Neoproterozoic diamictite from a profile of the Luoquan Formation on the southern margin of the North China Block (NCB). Upwards the sampling profile, lithostratigraphic strata vary from massive diamictite with poorly sorted carbonate gravels to laminated diamictite with small gravels of terrestrial detrital materials. Along the profile, CaO-MgO-LOI-Sr values decrease with the increase of SiO2-Al2O3-K2O contents. All these petrological and geochemical variations indicate a change from lodgement till deposition in the proximal of ice sheet to ice-rafting deposition in glacial-marine environment with less dolomite to supply their source. Together with previous studies on diamictite from other outcrops on the NCB, the deposition of Luoquan diamictite reflects that the glaciation on the NCB vanished and the ice-rafting effect weakened with glacial transgression process. In addition, significant co-variations of various elements with La and Al2O3 confirm the significant conservation of most analyzed elements during the sedimentary processes to produce diamictite.

Abstract Daqingshan is located in the northwestern North China Craton where late Neoarchaean supracrustal rocks occur widely, but where magmatic zircon ages have rarely been reported for plutonic rocks. In this study, we report SIMS U–Pb zircon ages and Hf isotope, whole-rock element and Nd isotope compositions for 12 magmatic samples, including TTG, quartz monzonitic and monzogranitic gneisses, and meta-gabbroic and dioritic rocks. They have magmatic zircon ages of 2530–2469 Ma; some samples have ages of <2.48 Ga likely influenced by late Palaeoproterozoic tectonothermal events, making their ages less reliable. TTG gneisses have low Sr/Y and La/Yb ratios, with whole-rock ϵNd(t) and in situ magmatic zircon ϵHf(t) values of +1.2 to +2.4 and −1.1 to +6.2, respectively. Quartz monzonite and monzogranite gneisses and gabbroic to dioritic rocks have similar Nd–Hf isotope compositions to the TTG gneisses. The absence of zircon >2.6 Ga in the early Precambrian rocks suggests that the Sanggan Group may have formed in an oceanic environment, whereas the TTG rocks formed as a result of partial melting of the basaltic rocks of the Sanggan Group under relatively low-pressure conditions. Combined with previous studies, the main conclusions are that in the Daqingshan area, late Neoarchaean magmatism was widespread, the late Mesoarchaean – early Neoarchaean was an important period of juvenile continental crustal growth, and the late Neoarchaean supracrustal and plutonic rocks most likely formed in an arc environment. These are common signatures for Neoarchaean crustal evolution throughout much of the North China Craton, and also globally.

Impact glasses found in lunar soils provide a possible window into the impact history of the inner solar system. However, their use for precise reconstruction of this history is limited by an incomplete understanding of the physical mechanisms responsible for their origin and distribution and possible relationships to local and regional geology. Here, we report U-Pb isotopic dates and chemical compositions of impact glasses from the Chang'e-5 soil and quantitative models of impact melt formation and ejection that account for the compositions of these glasses. The predominantly local provenance indicated by their compositions, which constrains transport distances to <~150 kilometers, and the age-frequency distribution are consistent with formation mainly in impact craters 1 to 5 kilometers in diameter. Based on geological mapping and impact cratering theory, we tentatively identify specific craters on the basaltic unit sampled by Chang'e-5 that may have produced these glasses and compare their ages with the impact record of the asteroid belt.

Zircon oxygen isotope ratios have been used to trace the incorporation of sedimentary rocks into magmas. The dramatic increase in maximum zircon delta O-18 values in the Paleoproterozoic observed in global databases coincides with changes in surface environments (e.g., the rise of subaerial and oxidative weathering), implying a connection between elevated zircon delta O-18 and these changes. Zircon delta 18O between 2.5 and 2.2 Ga, however, is relatively under-constrained owing to limited available data in this age range. To augment data from this critical time period and understand potential causes for the elevated zircon delta O-18 values, we report U-Pb zircon ages and delta O-18 values of zircon, as well as, whole-rock major and trace element geochemistry of Paleoproterozoic strongly peraluminous granites (SPGs) from the southwestern margin of the Yangtze Block (China). Our geochronological data demonstrate that these SPGs crystallized at -2.35 Ga and that inherited zircon with ages of 2428- 2721 Ma are present in these granites, indicating the source rocks of these granites were deposited, subsequently metamorphosed, and partially melted between 2.43 and 2.35 Ga. Synmagmatic zircon from samples dated in this study have cHf(t) values of -6.4 to -0.9 and high delta O-18 values of 7.6-9.9%0, elevated above the maximum value observed in Archean zircon (-7%0). These granites can be divided into two groups based on whole-rock geochemistry. Both Group 1 and Group 2 granites were derived from a similar high delta 18O, metapelitic source, but were generated by dehydration melting and hydrous melting, respectively. Our results demonstrate that the fine-grained sedimentary rocks from which the SPGs were derived had relatively high delta O-18 (as compared to older sedimentary rocks) by 2.43-2.35 Ga. The depositional time interval of the high delta O-18 sedimentary sources for SPGs studied here coincides with the emergence of continental crust above sea level and the Great Oxidation Event. Supporting the findings of previous studies, the contemporaneity of our dataset with these changes in Earth's surface environments suggests that subaerial and potentially oxidative weathering contributed (at least partially) to the elevation of delta O-18 of fine-grained sedimentary rocks. Recycling of these high-delta O-18 sedimentary rocks into magmas contributed to the dramatic change in delta 18O of magmatic zircon in the earliest Paleoproterozoic. In addition, although this study

珠一坳陷古近纪陆相湖盆发育优质烃源岩,通过对文昌组、恩平组泥岩系统取样,进行常量、微量元素、同位素含量等分析,优选出对环境敏感的元素与元素比值,系统分析了珠一坳陷烃源岩形成时的古环境,包括古盐度、古水深、氧化还原条件、古气候及古水体的封闭性,并建立了有机碳与环境敏感元素比值的定量关系.开展优质烃源岩发育的水化学性质研究,明确研究区优质烃源岩形成演化所具有的古环境特征,最终探讨了文昌组优质烃源岩的发育模式.研究结果表明,珠一坳陷(除韩江凹陷无样本点)文昌期温暖略干气候条件下,湖盆水体主要为淡水—微咸水,发育中—深湖相,整体表现为开放—半封闭、还原—强还原的环境,极利于有机质的保存和优质烃源岩的发育,各凹陷古环境差异不大.烃源岩质量与咸度、水深、还原条件呈正相关,共同影响了优质烃源岩的发育.总之,温暖略干、微咸、深水及强还原、开放—半封闭环境共同控制了珠一坳陷优质烃源岩的发育.

Hundreds of millions of tons of oil and gas geological reserves have been discovered through exploration in the deep-water area of the northern continental margin of the South China Sea, and the distribution of large-scale effective reservoirs during the Paleogene rifting period is the key for continuous discovery in deep-water zone. Large braided fluvio-delta can be observed on seismic data from the Wenchang to Enping formations in the rifting period of the flexural gentle slope belt in the deep-water zone. Due to the absence of wells or few wells, for further understanding of the composition and evolution of large braided fluvio-deltaic sedimentary units in the process of tectonic subsidence in this region, a simulation experiment on the response of the deltaic sedimentation process in the flexural gentle slope zone to flume was carried out. Three phases of tectonic subsidence were designed for the simulation experiment, corresponding to the three phases of Paleogene regional tectonic-sedimentary evolution including balanced rifting period, detached rifting period, and faulted depression rifting period. The hydrodynamic mechanism of tractive flow was simulated by means of flood, flat water, and dry water. Simulation results showed that during the three stages of tectonic subsidence, the flexural gentle slope zone deve-loped distributary channels, natural dikes, floodplains, underwater distributary channels, estuaries, inter-tributary bays and other delta sedimentary microfacies units. The braided river delta was dominated by lateral proliferation, supplemented by vertical accretion, and the sedimentary center gradually migrated to the center of the depression, with almost no degeneration. The delta shape and sand body distribution in the flexural gentle slope zone during the rifting period were mainly controlled by factors such as structural geomorphology, river discharge amount into lake, lake level changes, and water depth.

珠江口盆地西江凹陷南部包括两个相邻洼陷:西江36洼和番禺4洼,钻探结果却揭示了截然不同的油气勘探前景,其中,番禺4洼探明储量已过亿吨,而西江36洼却未有商业发现,导致勘探上对西江36洼烃源潜力有所顾虑.为了揭示这种差异油气地质条件产生的原因,亟待开展两个洼陷的对比研究.以主要烃源层系文昌组为切入点,通过开展精细的层序-沉积研究,进一步系统评估西江36洼烃源潜力.依据地震、钻井及分析化验等资料,在西江36洼与番禺4洼文昌组共识别了6个三级层序.西江36洼和番禺4洼文昌组发育扇三角洲、辫状河三角洲、湖底扇及湖泊沉积等沉积相类型,垂向上沉积相带具有旋回特征.伴随裂陷不同阶段和边界断层活动差异,陡坡带和缓坡带三角洲沉积体系规模呈现差异演化特征,而湖盆和半深湖-深湖相规模总体呈现出先增大后减小的规律.沉积相带在横向上也具有明显的迁移特征,表现为文六段时期先在西江36洼开始沉积,文五段开始再扩展到番禺4洼,同时文一段时期西江36洼湖盆已经消失,只在番禺4洼沉积充填.进一步对比两个洼陷各三级层序反映优质烃源岩条件的半深湖-深湖规模及物源供给量,结果显示在文六段至文四段时期两个洼陷烃源条件基本一致.鉴于该层段作为番禺4洼的主力源岩,其巨大的生烃潜力已经被勘探所证实,因此认为不能低估具有相似烃源条件的西江36洼生烃潜力.