Complex genesis of multiperiod fractures in the Middle Triassic Leikoupo Formation in the Pengzhou gas field, western Sichuan Basin, China

The cumulative expression of multistage deformation is complex multiperiod fractures,which are commonly seen in tectonic zones.The Middle Triassic Leikoupo Formation in the western Sichuan Basin Depression,China,is a typical marine carbonate reservoir with natural fractures caused mainly by tectonic movements.According to outcrops,drill cores,image logging,and fluid inclusions,the fracture characteristics,types of natural fractures,and interactions of fractures are determined.In total,419 natural fractures in 493.2 m of cores from 7 wells are investigated,which are mainly shear and tensile fractures with a small number of weathering generated fractures.Meanwhile,the results of the stable isotope analysis of δ13C and δ18O,as well as the flow fluid inclusion data,reveal four tectonic periods of fractures with different occurrences.Based on the history of regional tectonic evolution,indicating one period of weathering fractures ascribable to stratal uplift and three periods of structural fractures related to the sequential tectonic movements of the Longmenshan fault belt.By analyzing the interaction relationships of fractures,three types of fracture interaction relationships are observed:cutting,restraining,and overlapping.The four stages fractures are chronologically assigned to(1)the early Indosinian N-S trending compression,(2)the late Indosinian NW-SE compression,(3)the middle Yanshanian NE-SE compression,and(4)the early Himalayan E-W compression.The influence of natural fractures on gas migration and well production in marine carbonates is discussed,and indicates that tectonic fractures could provide seepage channels for gas migration and accumulation from near or distant hydrocarbon source rocks into the Middle Triassic Leikoupo Formation.This study utilizes a pragmatic approach for understanding the fracture genesis mechanism in oil and gas field with multiperiod fractures.

The Relationship Between Indian Ocean SST and Tropical Cyclone Genesis Frequency over North Indian Ocean in May

Tropical cyclone(TC)activities in the North Indian Ocean(NIO)peak in May during the pre-monsoon period,but the TC frequency shows obvious inter-annual variations.By conducting statistical analysis and dynamic diagnosis of long-term data from 1948 to 2016,the relationship between the inter-annual variations of Indian Ocean SST and NIO TC genesis frequency in May is analyzed in this paper.Furthermore,the potential mechanism concerning the effect of SST anomaly on TC frequency is also investigated.The findings are as follows:1)there is a broadly consistent negative correlation between NIO TC frequency in May and SST in the Indian Ocean from March to May,with the key influencing area located in the southwestern Indian Ocean(SWIO);2)the anomalies of SST in SWIO(SWIO-SST)are closely related to a teleconnection pattern surrounding the Indian Ocean,which can significantly modulate the high-level divergence,mid-level vertical motion and other related environmental factors and ultimately influence the formation of TCs over the NIO;3)the increasing trend of SWIO-SST may play an essential role in the downward trend of NIO TC frequency over the past 69 years.

Glass inclusions in volcanic rocks in the Okinawa Trough back-arc basin: constraints on magma genesis and evolution

The major element compositions of glass inclusions in plagioclase and pyroxene phenocrysts of basalt and pumice in the Okinawa Trough back-arc basin are determined by electron microprobe. The results indicate that basalt and pumice are cognate and respectively represent the products at early stages of magmatism and at late stage of crystal fractionation. The initial magma in the trough is rich in H2O. The variation of H2O content in magma may play an important role in the magma evolution. Plagioclase is the mineral crystallized throughout the whole magmatic process and accumulates in the zoned magma chamber. From these features it can be inferred that the initial magma in the Okinawa Trough, whose opening began in recent years, is seriously affected by fluid or other materials carried by subducting slab and the geochemical feature of volcanic rocks is in some degree similar to that of lavas in island-arc environments.

Geochemistry and Petrogenesis of Basic and Ultrabasic Rocks Elogo Complex in Ivindo Archean Block (Congo Craton): Geodynamic Implications

The Elogo complex is a greenstone belt portion located on the Eastern edge of the Archean Congo craton at the junction with the Paleoproterozoic to Neoproterozoic Sembe Ouesso basin. This study was carried out on this complex to determine the context of the placement of basaltic rocks. Metaluminous tholeiitic basalts (basic and ultrabasic), calc-alkaline basalts, andesitic basalts, and peraluminous calc-alkaline dacites represent greenstones. Tholeiitic and calc-alkaline basalts come from deep enriched and depleted mantle sources, including garnet in fusion residues [Al2O3/TiO2 > 16 (16.5 to 35.12) and in some samples between 12.45 to 14.48;CaO/Al2O3 1 (1.04 to 1.35) in ten samples and (Gb/Yb)PM > 1]. The calc-alkaline dacites come from a shallow depleted mantle source [Al2O3/TiO2 > 16;CaO/Al2O3 1]. Tholeiitic and calc-alkaline basalts have a negative Rb, Ba, Ce, and Nb anomaly without negative Ti anomaly, positive Ta, Pb anomalies, and a lack of significant REE [(La/Yb)n = 0.36 to 0.97 and 1 to 2.15;(Ce/Yb)n = 0.27 to 0.96 and 1.04 to 1.72, respectively] fractionation. High Nb/Th (2 to 10) and Nb/U (1.82 to 26) ratios and low La/Ta (5 to 27) ratios are characteristic of divergent margin magmatic sources. Tholeiitic and calc-alkaline basalts correspond to an extensive back-arc basin-type tectonic setting. Calc-alkaline andesitic basalts and dacites show positive Ba, U, Th, K, La, Ce, Pb, and Li anomalies and negative Nb, Ta, and Ti anomalies reflecting crustal contamination and hydrothermal alteration in a compressive tectonic context as a volcanic arc in a subduction regime marking the interruption of the meso-neoarchean Elogo’s opening. Elogo’s opening and closing are probably associated with the emplacement of the greenstone of the meso-neoarchean Gabon Belinga group and the relics of the Mesoarchean greenstones of the Cameroun Ntem complex.

Petrogenesis and tectonic implications of Indosinian granitoids from Western Qinling Orogen,China:Products of magma-mixing and fractionation

The Western Qinling Orogen(WQO) is characterized by voluminous distribution of Indosinian granitoids,the formation of which provides an important window to unravel the geochemical and geodynamic evolution and associated metallogeny.Here we investigate a group of intrusions termed "Five Golden Flowers" based on petrological,geochemical,zircon U-Pb geochronological and Lu-Hf isotopic studies on the granitoids and their mafic microgranular enclaves(MMEs).Our results show that these intrusions are genetically divided into two types,namely,magma-mixing and highly fractionated.The Jiaochangba,Lujing,Zhongchuan,and Luchuba granitoids are biotite monzogranites(220±0.8 Ma to 217±2.6 Ma) with abundant coeval MMEs(220±.1 Ma to 217±2.7 Ma).The rocks contain moderate to high SiO2,high MgO,Rb,Sr,Ba,and Th contents,but low TiO2,P2 O5,and Sc values,A/CNK of <1.1,and a range of εHf(t) values of-11.7 to +2.23 with corresponding TDM2values of 1967-1228 Ma.The MMEs possess K-feldspar megacrysts,abundant acicular apatites,and show lopsided textures.They have lower SiO2,Al2 O3,and Th contents,but higher MgO,TiO2,and Sc,with εHf(t) values of-18.0 to +3.18 and TDM1 of 849-720 Ma.The data indicate that the MMEs were derived from a magma sourced from the enriched lithospheric mantle.We suggest that these host granitoids were produced by partial melting of latePaleoproterozoic to early-Mesoproterozoic lower crust with the involvement of Neoproterozoic SCLM-derived mafic magmas.The Baijiazhuang pluton is dominantly composed of leucogranite(muscovite granite and twomica monzogranite,216±1.5 Ma) without MMEs.The rocks are peraluminous with high A/CNK(1.06-1.27).Compared with the other four granitoids,the Baijiazhuang leucogranite shows higher SiO2 content,markedly lower concentrations of TiO2,MgO,Al2 O3,CaO,and Fe2 O3T,and lower LREE/HREE and(La/Yb)N values.These leucogranites are also rich in Rb,Th,and U,and display marked depletions in Ba,Sr,Ti,and Eu,indicating that they experienced significant fractionation.Zircon εHf(t) values(-10.2 to-3.27) and TDM2(1868-1424 Ma),as well as the Nb/Ta and K2 O/Na2 O values are similar to the other four granitoids,indicating that they are likely to have been derived from a similar source;with sediments playing only a minor role in the magma generation.The low contents of Yb and Y suggest that their partial melting was controlled by garnets and micrographic texture of K-feldspar reflects high-temperature melting through undercooling.Based on the above features,we infer that the Baijiazhuang leucogranite likely represents the product of high degree fractionation of the I-type biotite monzogranite magma which generated the other four granitoids at relatively high temperatures,within magma chambers at mid-crust depths.We propose that the granitoid suite was formed in the transitional setting from synto post-collision during the collisional orogeny between the SCB and NCB,following break-off of the subducted South China Block lithosphere during 220-216 Ma.

Magma-Fluid Transition and the Genesis of Pegmatite Dike No.3,Altay,Xinjiang,Northwest China

Abstract: The physico-chemical conditions under which the pegmatite dyke No. 3 was formed were discussed in the light of fluid-melt inclusion evidence. Our results lend support to the frac-tionation of hydrothermal solutions from magma. For the pegmatite dike No. 3, the magma-derived hydrothermal solutions are dominated by NaCl + CO2 + H2O.

Genesis, metallogenic model, and prospecting prediction of the Nibao gold deposit in the Guizhou Province, China

Southwestern Guizhou province is one of China’s most important distribution areas of Carlin-type gold deposits. The Nibao deposit is a typical gold deposit in southwestern Guizhou. To elucidate the genesis of the Nibao gold deposit, establish a metallogenic model, and guide prospecting prediction, we systematically collected previously reported geological, geochemical, and dating data and discussed the genesis of the Nibao gold deposit,based on which we proposed the metallogenic model.Earlier works show that the Nibao anticline, F1 fault, and its hanging wall dragged anticline(Erlongqiangbao anticline) were formed before or simultaneously with gold mineralization, while F2, F3, and F4 faults postdate gold mineralization. Regional geophysical data showed extensive low resistivity anomaly areas near the SBT(the product of tectonic slippage and hydrothermal alteration)between the P2/P3 and the strata of the Longtan Formation in the SSE direction of Nibao anticline in the lower plate of F1 and hanging wall dragged anticline(Erlongqiangbao anticline), and the anomaly areas are distributed within the influence range of anticlines. Simultaneously, soil and structural geochemistry show that F1, Nibao anticline,Erlongqiangbao anticline, and their transition areas all show good metallogenic elements(Au, As, and S) assemblage anomalies, with good metallogenic space and prospecting possibilities. There are five main hypotheses about the source of ore-forming fluids and Au in the Nibao gold deposit:(1) related to the Emeishan mantle plume activity;(2) source from the Emeishan basalt;(3) metamorphic fluid mineralization;(4) basin fluid mineralization;(5) related to deep concealed magmatic rocks;of these, the mainstream understanding is the fifth speculation. It is acknowledged that the ore-forming fluids are hydrothermal fluids with medium–low temperature, high pressure, medium–low salinity, low density, low oxygen fugacity, weak acidity, weak reduction, and rich in CO_(2)and CH_(4). The fluid pressure is 2–96.54 MPa, corresponding to depths of 0.23–3.64 km. The dating results show that the metallogenic age is ~141 Ma, the extensional tectonic environment related to the westward subduction of the Pacific Plate. Based on the above explanation, the genetic model related to deep concealed magmatic rocks of the Nibao gold deposit is established, and favorable prospecting areas are outlined;this is of great significance for regional mineral exploration and studying the genesis of gold deposits.

A Scenario for Asymmetric Genesis of Matter

A previous preon scenario for the standard model particles, based on unbroken supersymmetry, is applied to the problem of matter-antimatter asymmetry. Attention is paid to the fact that the asymmetric hydrogen atom—like all atoms—can be described in terms of symmetric preons. Preons are created in the early universe. The matter-antimatter asymmetry is caused by stochastic correlations in charge density fluctuations of preons and antipreons and by the subsequent preon combinatorial mechanism to form quarks and leptons, and finally the three lightest elements. A tentative gravitino mass estimate is given based on minimal interference with nucleosynthesis. With local supersymmetry the scenario can be extended to supergravity.

Petrogenesis of the microcrystalline-dioritic enclaves from Jiuling granitoids in the eastern segment of Jiangnan Orogen and constraints on magma source materials

Numerous dark enclaves with different shapes are found in Jiuling Neoproterozoic granitoids.Precise LAICP-MS U-Pb dating was conducted on zircons extracted from two microcrystalline enclave samples,yielding crystallization ages of 822.6±5.8 Ma and 822.2±6.2 Ma,respectively.The consistent ages within analytical errors with the host granitoids suggested that they were the products of the same magmatism.The microcrystalline-dioritic enclaves commonly show plastic forms and contain similar plagioclase megacrysts to the host rocks,and both of the enclaves and host granitoids showed a complex composition and structural imbalance in plagioclases.Furthermore,the apatites with a euhedral acicular shape occurred widely in the microcrystalline-dioritic enclaves.All of these petrographic features above imply magma mixing is involved in their diagenesis.The enclaves and host granitoids show a marked zircon trace element difference and Hf isotopic signatures without correlation in zircon trace element pairs but form their own system between enclaves and host granitoids.Additionally,most of the zircons show extremely high εHf (t) with εHf (t) =3.54?11.94 from the southern samples,and εHf (t) =1.0?9.09 from the central region.Some zircons with the higher εHf (t) are similar to the zircons from the juvenile island arc in the eastern segment of Jiangnan Orogen.Integrated geological and Hf isotopic characteristics suggest microcrystalline-dioritic enclaves were derived from the partial melting process of the Mesoproterozoic crust which enriched juvenile island arc materials and mixed with the granitic magma that remelted from the Mesoproterozoic continental crust which relatively enriched ancient sediments and mixed with the host granitoid in diagenesis.

Source Enrichment Control on the Scale of Magmatic-Hydrothermal W-Sn Mineralization:Insights from Triassic and Jurassic Magma Reservoirs in the Continental Crust,Xitian,South China

There are two factors,source composition and magmatic differentiation,potentially controlling W-Sn mineralization.Which one is more important is widely debated and may need to be determined for each individual deposit.The Xitian granite batholith located in South China is a natural laboratory for investigating the above problem.It consists essentially of two separate components,formed in the Triassic at ca.226 Ma and Jurassic at ca.152 Ma,respectively.The Triassic and Jurassic rocks are both composed of porphyritic and fine-grained phases.The latter resulted from highlydifferentiated porphyritic ones but they have similar textural characteristics and mineral assemblages,indicating that they reached a similar degree of crystal fractionation.Although both fine-grained phases are highly differentiated with elevated rare metal contents,economic W–Sn mineralization is rare in the Triassic granitoids and this can be attributed to less fertile source materials than their Jurassic counterparts,with a slightly more enriched isotopic signature and whole-rockεNd(226 Ma)of−10.4 to−9.2(2σ=0.2)compared withεNd(152 Ma)of−9.2 to−8.2(2σ=0.2)for the Jurassic rocks.The initial W-Sn enrichment was derived from the metasedimentary rocks and strongly enhanced by reworking of the continental crust,culminating in the Jurassic.

Sr and Nd Isotopic Characteristics and Magma Genesis of Mesozoic Volcanic Rocks Along the Coastal Region of Southeastern China

The Mesozoic volcanic rocks in the coastal region of southeastern China were superimposed on some different basement tectonic elements. The volcanic rocks developed in these different basement tectonic elements have great differences in Sr and Nd isotopic compositions. The rocks in western Zhejiang and northeastern Jiangxi Provinces which belong to the Lower Yangtze subplate have lower initial 87Sr/ 86Sr ratios, but are higher in initial Nd isotopic ratios. The initial 143Nd / 144Nd values of the volcanic rocks developed in the Cathaysian subplate increase clearly from early to late in time, and from the core of the Wuyishan uplift coastwards constantly, but the initial 87Sr/86Sr values tend to decrease. The isotopic characteristics and their spatial variations in Mesozoic volcanic rocks in the study region are, to a great extent, manifestations of the isotopic characteristics in basement metamorphic complexes, and the generation of the Mesozoic acid magma in this region is attributed to the recycling of pre-existing crustal materials.

Petrogenesis of the Lunar volcanic glasses and Mg-suite:constraints on a post-magma-ocean cumulate overturn

The lunar volcanic glasses and Mg-suite rocks represent the early enigmatic episodes of lunar magmatism.Due to the gravitational instability of the Fe-Ti enriched(±KREEP)layer,which is formed at the later stage of fractional crystallization,a post-magma-ocean cumulate overturn occurred contemporaneously or near-contemporaneously with the lunar magma ocean(LMO)solidification.The radioactive elements within the KREEP layer were transferred downward and provided continuous energy for the partial melting of the Moon’s interior.The melt from the Moon’s interior and those from decompression melting,in turn,provide source magma for the origin of lunar volcanic glasses and Mg-suite.However,experimental and theoretical studies on the formation process of lunar volcanic glasses and Mg-suite show that the origin of their parental magma is poorly constrained,which largely depends on the initial depth and composition of the LMO.This review examines the mineralogy,petrogenesis,and distribution of lunar volcanic glasses and Mg-suite.Combining with existing models,we constrain the degree,distribution,and timescale of lunar mantle overturn and explore their relationship with later stages of LMO differentiation.We propose an updated chemical composition of the lunar interior,which provides a useful reference for estimating the bulk composition and early differentiation of the Moon and the early Earth.

New Data on the Genesis and Evolution of the Primitive Magmas of Mount Cameroon: Contribution of Melt Inclusions

Mount Cameroon is a Plio-Quaternary volcanic massif, without a centralcrater, made up of more than 140 pyroclastic cones. It is one of theactive volcanoes of the Cameroon Volcanic Line. Mount Cameroon meltinclusions are found in microdroplets trapped in the early minerals (olivines)from the pyroclastic products. The analysis of these melt inclusions allowedus to find primitive liquids compared to lavas. Major elements study ofthe magmatic inclusions, trapped in the most magnesian olivines (Mg#84-86) of Mount Cameroon revealed “primitive” liquids of basanite and alkalibasalt type with variable composition compared to the much more uniformbasalts of the magmatic series of Mount Cameroon. The study of thesetrapped liquids shows that: (1) the original primitive lavas did not undergothe process of evolution by FC, but rather underwent fundamentally (orexclusively) the process of partial melting;(2) the emitted lavas, evolvedessentially by FC;(3) the variations in the trace element contents of theprimitive liquids directly reflect a variation in the rate of partial melting ofa homogeneous mantelic source. The very high La/Yb ratios of the MountCameroon melt inclusions (> 20) characterize a garnet lherzolite source.Spectra of the melt inclusions show a negative anomaly or depletion in K,Rb and Ba as those of HIMU. The “primitive” liquids and lavas of MountCameroon represent a co-genetic sequence formed by varying degrees ofpartial melting of a source considered as homogeneous.

Genesis and Distribution of Ultra-alkaline Magmatism within the East Antarctic Associated with the Kerguelen Plume Activity

Alkaline magmatism is often associated with the initial or final stages of huge plume activity.The alkaline bodies are most often found within the boundary area of plume impact upon the continents.The initial stages of the

GENESIS诱导小麦雄性不育性与花药组织呼吸关系的初步研究

对小麦小孢子发育的各个时期,经GENESIS处理的和未处理的植株花药的总呼吸活性 Vt 、细胞色素途径呼吸活性 ρ′Vcyt 和交替途径实际呼吸活性 ρValt 进行了比较研究,结果表明,在各时期,处理植株花药的Vt呼吸均低于未处理植株,尤以单核期最为明显;在小孢子减数分裂期、四分体期和单核期,处理小麦植株花药的ρ′Vcyt均明显降低,而在小孢子减数分裂期和四分体期ρValt出现明显升高.结论认为,由呼吸过程中电子传递途径运行的改变而造成处理植株花药呼吸代谢的紊乱,可能是GENESIS诱导小麦雄性不育发生的重要原因.

GENESIS诱导小麦雄性不育与幼穗中乙烯含量的关系

在小麦发育的 Feekes8.5时期用化学杂交剂 GENESIS进行处理 ,分别在小麦花药发育的单核期、二核期和三核期测定幼穗中乙烯释放量的变化 ,研究 GENESIS诱导小麦雄性不育与乙烯的关系。结果表明 :经化学杂交剂 GENESIS诱导后 ,幼穗中乙烯释放量在 3个时期均明显高于对照。随着 GENESIS喷施剂量的增加 ,诱导小麦雄性不育率也相应增加 ,同时幼穗中乙烯释放量也表现出相同的增长趋势。表明 GENESIS诱导小麦雄性不育的生化机理在于 GENESIS诱导小麦幼穗中乙烯释放量增加 ,乙烯释放量的变化与小麦雄性不育有直接关系。同时 ,利用乙烯合成抑制剂 (AVG)处理细胞核质互作雄性不育系后 ,内源乙烯释放速率降低 。

GENESIS诱导小麦雄性不育活性窗口研究

在小麦大小分蘖达到适宜喷药期 ,而部分主茎 (大约 1%左右 )已经超过 Feeks9.0的情况下 ,为了检测GENESIS是否能有效地抑制这类主茎的自交结实 ,选择了 2 0个优势群亲本基因型小麦品种 (系 )进行了试验。结果表明 ,当小麦生长时期处于 Feeks9.0～ 9.8时 ,进行一次叶面喷施 ,所有参试品种仍可达到 95 %以上的杀雄效果 ,能够有效地抑制小麦自交结实 ,同时对其中 10个参试小麦品种进行人工饱和授粉 ,证明 GENESIS对雌蕊的育性没有明显影响。

化学杂交剂GENESIS对小麦生长发育的影响

采用 8个基因型 ,4个剂量的裂区试验 ,对新型化学杂交剂GENESIS完全诱导小麦雄性不育时的人工饱和授粉结实率、农艺性状表现、种子发芽势和发芽率进行了比较研究。结果表明 :3.0kg/hm2 、5 .0kg/hm2 剂量的雄性不育率达到或接近 10 0 %时 ,人工饱和授粉最高结实率分别为 84 .72 %、6 6 .71% ,前者超对照 11.13% ,后者与对照相近 ,但较 3.0kg/hm2 减少 11.4 8%。GENESIS对小麦抽穗期和株高没有不良效应 ;5 .0kg/hm2 时千粒重较对照减少1.1g;籽粒的发芽势、发芽率和产量明显低于对照 。

化学杂交剂GENESIS对小麦的杀雄效果

采用 4个品种 ,4个剂量 ,2个表面活性剂的裂区试验和 2个品种的异地试验 ,对新型化学杂交剂GENESIS诱导小麦雄性不育的效果进行了研究。结果表明 :( 1)GENESIS杀雄彻底 ,2 0kg/hm2 以上剂量的不育率均超过 95 % ,3 0、 5 0kg/hm2 剂量达到或接近 10 0 % ,且没有诱导小麦雄性不育的专一性 ;( 2 )不育率为 95 %以上的人工饱和授粉结实率和自然授粉结实率最高达 6 7 6 5 %和 49 83% ;( 3) 5 0kg/hm2 剂量下 ,添加表面活性剂MON816 1的人工饱和授粉结实率比添加MON5 916 0的降低 18 9% ,差异显著。说明表面活性剂MON816 1对雌蕊的活力具有一定影响 ;( 4)相同基因型在两个地点的不育率和自然授粉结实率差异不显著 。

化学杀雄剂GENESIS诱导早熟禾雄性不育的初步研究

试用美国新近生产的化学杀雄剂 GENESIS对早熟禾进行雄性不育的初步研究。结果表明 ,参试的 4个品种瓦巴斯草地早熟禾、思托佩草地早熟禾、天祝扁秆早熟禾与莫诺波利草地早熟禾在生育期 Feekes标准 8.0～ 9.0时 ,用 GENESIS进行一次叶面喷施 ,在 1. 5kg/ hm2 和 2 .5kg/ hm2 的剂量下 ,天祝扁秆早熟禾的杀雄效果为 95%和 97% ,其它品种均为10 0 %