The unique skeleton of siliceous sponges (Porifera; Hexactinellida and Demospongiae) that evolved first from the Urmetazoa during the Proterozoic: a review

Sponges (phylum Porifera) had been considered as an enigmatic phylum, prior to the analysis of their genetic repertoire/tool kit. Already with the isolation of the first adhesion molecule, galectin, it became clear that the sequences of sponge cell surface receptors and of molecules forming the intracellular signal transduction pathways triggered by them, share high similarity with those identified in other metazoan phyla. These studies demonstrated that all metazoan phyla, including Porifera, originate from one common ancestor, the Urmetazoa. The sponges evolved prior to the Ediacaran-Cambrian boundary (542 million years ago [myr]) during two major "snowball earth events", the Sturtian glaciation (710 to 680 myr) and the Varanger-Marinoan ice ages (605 to 585 myr). During this period the ocean was richer in silica due to the silicate weathering. The oldest sponge fossils (Hexactinellida) have been described from Australia, China and Mongolia and are thought to have existed coeval with the diverse Ediacara fauna. Only little younger are the fossils discovered in the Sansha section in Hunan (Early Cambrian; China). It has been proposed that only the sponges possessed the genetic repertoire to cope with the adverse conditions, e.g. temperature-protection molecules or proteins protecting them against ultraviolet radiation. The skeletal elements of the Hexactinellida (model organisms Monorhaphis chuni and Monorhaphis intermedia or Hyalonema sieboldi) and Demospongiae (models Suberites domuncula and Geodia cydonium), the spicules, are formed enzymatically by the anabolic enzyme silicatein and the catabolic enzyme silicase. Both, the spicules of Hexactinellida and of Demospongiae, comprise a central axial canal and an axial filament which harbors the silicatein. After intracellular formation of the first lamella around the channel and the subsequent extracellular apposition of further lamellae the spicules are completed in a net formed of collagen fibers. The data summarized here substantiate that with the finding of silicatein a new aera in the field of bio/inorganic chemistry started. For the first time strategies could be formulated and experimentally proven that allow the formation/synthesis of inorganic structures by organic molecules. These findings are not only of importance for the further understanding of basic pathways in the body plan formation of sponges but also of eminent importance for applied/commercial processes in a sustainable use of biomolecules for novel bio/inorganic materials.

济阳坳陷深层地质构造与演化

Based on geophysical and geological data in Jiyang depression, the paper has identified main unconformity surfaces (main movement surfaces) and tectonic sequences and established tectonic and strata framework for correlation between different sags. Based on different sorts of structural styles and characteristics of typical structures, the paper summarized characteristics and distribution of deep structures, discussed evolution sequence of structure, analyzed the relation between tectonic evolution and generation of petroleum. The major developments are as following: Six tectonic sequences could be divided from bottom to top in the deep zone of Jiyang depression. These tectonic sequences are Cambrian to Ordovician, Carboniferous to Permian, lower to middle Jurassic, upper Jurassic to lower Cretaceous, upper Cretaceous and Kongdian formation to the fourth member of Shahejie formation. The center of sedimentation and subsidence of tectonic sequences distinguished from each other in seismic profiles is controlled by tectonic movements. Six tectonic evolution stages could be summarized in the deep zone in Jiyang depression. Among these stages, Paleozoic stage is croton sedimentation basin; Indosinian stage, open folds of EW direction are controlled by compression of nearly SN direction in early Indosinian (early to middle Triassic) while fold thrust fault of EW – NWW direction and arch protruding to NNE direction are controlled by strong compression in late Indosinian (latter Triassic); early Yanshanian stage (early to middle Jurassic), in relatively weak movement after Indosinian compressional orogeny, fluviolacustrine is deposited in intermontane basins in the beginning of early Yanshanian and then extensively denudated in the main orogenic phase; middle Yanshanian (late Jurassic to early Cretaceous), strike-slipping basins are wide distribution with extension (negative reversion) of NW – SE direction; latter Yanshanian (late Cretaceous), fold and thrust of NE – NNE direction and positive reversion structure of late Jurassic to early Cretaceous strike-slipping basin are formed by strong compression of NW–SE direction; sedimentation stage of Kongdian formation to the fourth member of Shahejie formation of Cenozoic, half graben basins are formed by extension of SN direction early while uplift is resulted from compression of nearly EW direction latterly. Compression system, extension system and strike-slip system are formed in deep zone of Jiyang depression. According to identifying flower structure of seismic profiles and analysis of leveling layer slice of 3D seismic data and tectonic map of deep tectonic interface, strike-slip structures of deep zone in Jiyang depression are distinguished. In the middle of the Jiyang depression, strike-slip structures extend as SN direction, NNW direction in Huimin sag, but NNE in Zhandong area. Based on map of relict strata thickness, main faults activity and regional tectonic setting, dynamic mechanisms of deep structure are preliminary determination. The main reason is the difference of direction and character of the plate’s movement. Development and rework of multi-stage tectonic effects are benefit for favorable reservoir and structural trap. Based on tectonic development, accumulation conditions of deep sub-sags and exploration achievements in recent years, potential zones of oil-gas reservoir are put forward, such as Dongying sag and Bonan sag.

西天山造山带古生代构造演化与地壳增生—来自花岗岩和蛇绿岩的证据

The Central Asian Orogen Belt (CAOB), which is different from the subductional orogen and the collisional orogen, is known as the most important site of crustal growth in the Phanerozoic, and it has been a ‘hot spot’ for studying the orogenic belts. The Chinese West Tianshan Orogen is occupying the west-southern part of the CAOB and is of great importances to understand the orogenic processes and the continental growth in the Central Asia. The West Tianshan Orogen had undergone complex tectonic evolutional processes in Paleozoic times and large volumes granitic rocks have recorded important information about these processes. Litter is known about Phanerozoic continental growth in the Western Tianshan area so far, compared with the other areas of the CAOB, such as eastern Junggar, western Junggar, Altai and Alakol. The aim of this dissertation is to set up the chronology frame of granitoids in western Tianshan, provide new evidence for the tectonic evolution and discuss the Paleozoic continental growth in this area, on the basis of the studies on the isotopic chronology, major element, trace element and Nd-Sr isotopic geochemistry of granitoids and the isotopic chronology and geochemistry of the ophiolites in this area, especially the Kule Lake ophiolites. 25 precise SHRIMP U-Pb zircon and LA-ICPMS U-Pb zircon ages have been obtained in this dissertation. The granitic rocks in western Tianshan had been formed during two periods: the granitic gneiss with an age of 896Ma, possibly representing the forming age of the Precambrian basement; the granitic rocks with ages varying from 479Ma to 247Ma, recording the Paleozoic orogenic process of western Tianshan. The granitoids in western Tianshan are composed of intermediate-basic rocks, intermediate rocks, intermediate-acid rocks and acid rocks, mainly intermediate-acid rocks and acid rocks. They are mostly granite, granodiorite, quartz syenite and monzodiorite. Different types of granitic rocks are exposed in different tectonic units. The granitoids on the northern margin of the Yili Plate mainly formed in late Paleozoic (413Ma ~ 281Ma), those with ages varying from 413Ma to 297Ma show continental arc affinities and the magnesian calc-alkalic metaluminous diorite of 281Ma display the geochemical characteristics similar to those of granites formed during the post-orogenic period. The granitiods on the southern margin of the Yili Plate include the adakite diorite of 470Ma which was formd by partial melting of thickened lower crust, the post-collisional alkali-feldspar granite of 430Ma, the volcanic arc granite of 348Ma and the Triassic post-collisional granite. The granitoids in the Central Tianshan Plate formed in 479Ma ~ 247Ma, mainly in 433Ma ~ 321Ma. The granitic rocks with ages of 479Ma ~ 321Ma are magnesian calc-alkalic to alkalic rocks with continental arc affinities. A few post-collisional granitoids of 276Ma ~ 247Ma may have inherited the geochemical characteristics of pre-existing arc magma. The granitic rocks in Southern Tianshan (northern margin of the Tarim plate) formed two stages, 420Ma ~ 411Ma and ca. 285Ma. The magnesian calcic to alkalic granites of 420Ma ~ 411Ma may formed during the extension process of the continental margin. The granite of 285Ma includes mostly ferroan calc-alkalic to alkali-calcic rocks with high SiO2 and high alkaline contents, and obviously negative anomaly of Eu, Ba, Sr, P, Ti, similar to the geochemical characteristics of the A-type granite which is formed during post-collisional extension. The Kule Lake ophiolite in southern Tianshan shows the affinity of N-MORB. A SHRIMP zircon U-Pb age of 425±8Ma has obtained for gabbros. Some zircons have given another group of 206Pb/238U age 918Ma, which may indicate the information of the pre-exist old basement rock. The small oceanic basin represented by Kule Lake ophiolite probably developed on the split northern margin of Tarim block. A model for Paleozoic tectonic evolution of the West Tianshan Orogen has been proposed here on the basis of the new results obtained in this dissertation and the previous published data. In Early Cambrian, the Terskey Ocean occurred along the North Nalati fault (NNF), and it separated the Yili plate from the Central Tianshan plate which was probably connected with the Tarim plate. The Terskey Ocean probably subducted towards south under the Central Tianshan plate and towards north under the Yili plate simultaneously. In the early stage of Late Ordovician, the Terskey Ocean had been closed, and the Yili and Central Tianshan plates collided. Meanwhile, extension happened within the joint Central Tianshan and Tarim plates gradually and the Paleo-South Tianshan Ocean had been formed. In Early Silurian, the Paleo-South Tianshan Ocean began to subduct beneath the composite Yili-Central Tianshan plate, which was intruded by volcanic arc granitoids. In Middle Silurian, the Paleo-South Tianshan Ocean, which had reached a certain width, was subducting strongly. And this subduction may have produced voluminous granitoids in the Central Tianshan plate. In the latest stage of Carboniferous, the Paleo-South Tianshan ocean closed, and the Yili-Central Tianshan plate and Tarim plate collided. In Late Cambrian, Paleo-Junggar Ocean occurred to north of the Yili plate; and started to subduct towards south under the Yili plate in Ordovician. This subduction may have produced a magma arc on the northern margin of the Yili plate. In Late Carboniferous, the Paleo-Junggar Ocean had been closed. The Yili-Central and Junggar plates amalgamated together. The West Tianhan Orogen may undergo a post-collisional collapse since Permian. And the magmatic activities may continue to early Triassic. The initial 87Sr/86Sr ration of the granitic rocks in the western Tianshan Mountains varies from 0.703226 to 0.716343, and Nd（t）from -6.50 to 2.03. The characteristics of Sr-Nd isotope indicate that the source of granitic material is not a sole source, which may be produced by mantle-crust magma mixing. In Paleozoic time, lateral growth of the continental crust along active continental margins was dominant, whereas the vertical growth of continental crust resulted from post- collisional mantle derived magmas was not obvious.

牡丹江碰撞带的组成及演化

Jiamusi Massif is an important tectonic unit in Northeast China. It’s significant for understanding the evolution of Paleo-Asian Ocean and reconstruction of the tectonic framework of Northeast China. Mudanjiang area is located in the southern margin of Jiamusi Massif and is the key to understand the evolution of Jiamusi Massif. However, the detailed geological research for Mudanjiang area has long been deficient in many important problems, such as the tectonic components of the Mudanjiang collision zone (MCZ), the age of collisional complexes and the scenario of tectonic evolution. Based on the lithology, geochemistry and the SHRIMP zircon U-Pb geochronology in Mudanjiang area, our new data and results come to some constraints for the tectonic reconstruction of MCZ as follows: 1） It is identified that the former suggestion, which the so-called “Heilongjiang Group” in Mudanjiang area is the vestige of oceanic crust, is correct. The oceanic relics represent the Neo-Proterozoic-Early Paleozoic oceanic basins based on the SHRIMP zircon U-Pb geochronology. 2） One sheet of gabbroic complex with oceanic island-type geochemical signature was discovered by this work in Mudanjiang area. 3） It is verified that the Proterozoic concordant U-Pb ages of the migmatites developed along the southern margin of Jiamusi massif, which represent the events of magmatic intrusion, as the direct evidence for the existence of the Proterozoic crystalline basements of the Jiamusi Massif. Based on geochronology, we suggest that the migmatization and coeval S-type granite magmatism of the southern margin of Jiamusi Massif took place about 490Ma. 4） The island arc complex has been found in the Heilongjiang Group, and the oceanic relics was found distributing on both sides, as provided important constraint for the tectonic reconstruction of the MCZ. 5） ~440Ma metamorphic event and coeval post-collisional granite magmatism have been firmly identified in the MCZ and its southern neighboring area. Together with previous data obtained by other researchers, our conclusions on the reconstruction of the tectonic architecture and evolution of the MCZ as follows: 1） The orogenic assemblages developed in the Mudanjiang collisional zone are featured by a sequence of ancient active continental margins and ensuing orogenic processing. The Mashan Group is the reworking basement of Jiamusi Massif, whereas the Heilongjiang Group represents arc and oceanic complexes characterized by imbricate deep-seated sliced and slivering sheets due to multi-phases of thrusting and nappe stacking. 2） The northern sub-belt of MCZ is probably the arc-continent collisional boundary related to the closure of main oceanic basin. The collisional age can be constrained by the events of syn-orogenic migmatization of migmatite, coeval S-type granite magmatism and the related granulite-facies metamorphism. Therefore, we suggested the collisional age of northern sub-belt is probably Cambrian-Early Ordovician. The extensive granulite-facies metamorphism of the Mashan Group in Jiamusi Massif, as affirmed by former works, was probably related with the collisional event. 3） The southern sub-belt of the MCZ was possibly related with the closure of back-arc basin. We presumed that the collisional age of southern sub-belt is about Ordovician-Early Silurian according to the ~440Ma extensive metamorphism and the occurrence of coeval post-collisional granite magmatism. 4） The extant structural architecture of the MCZ is related to the multi-phases of intra-continental superimposition, which is characterized by the Mesozoic nappe structure.

塔里木盆地塔北、塔中地区早古生代白云岩形成机理

In Tarim Basin, extensive carbonates of Lower Paleozoic occur, in which thick Cambrian and Lower Ordovician dolostones are widespread and show a potential perspective in hydrocarbon exploration. So they are viewed as an important target for exploration. Tarim Basin is a poly phase composite basin, which underwent multiphase tectonic modification and volcanic activities; these exerted significant influences on the basin-fills and basin fluid evolution, thereby the diagenetic history, particularly on the deep-buried Lower Paleozoic dolostones. Referring to the classification of dolomite texture proposed by Gregg & Sibley (1984) and Sibley & Gregg (1987). In view of crystal size, crystal shape, crystal surface and contact relation, eight genetic textures of dolomite crystals are identified, based on careful petrographic examinatoins. These textures include: 1) micritic dolomite; 2) relict mimetic dolomite; 3)finely crystalline, planar-e(s), floating dolomite; 4)finely crystalline, planar-e(s) dolomite; 5) finely-coarse crystalline, nonplanar-a dolomite; 6)coarse crystalline, nonplanar saddle dolomite; 7) finely-medium crystalline, planar-e(s) dolomite cement; 8) coarse crystalline, nonplanar saddle dolomite cement, in which the former six textures occurs as in matrix, the latter two in the cements. Detailed geochemistry analysis is carried out on the basis of genetic textures of dolomite and related minerals such as quartz and calcite. The result showed that the calcite has the highest average content in Sr, which can be sorted into two groups; micritic dolomite has the highest average content in Sr among all kinds of dolomites; the REE patterns of all kinds of dolomites is similar to those of marine limestone samples. Saddle dolomite cement has δ13C values from -2.44‰ to 1.27‰ PDB, and δ18O values from -13.01‰ to -5.12‰ PDB, which partially overlap with those of matrix dolomite (δ13C values from -2.83‰ to 2.01‰ PDB, δ18O values from -10.63‰ to -0.85‰ PDB). Saddle dolomite cement has 87Sr/86Sr ratios from 0.7086 to 0.7104, which totally overlap with those of matrix dolomite (0.7084 ~ 0.7116). Compared with saddle dolomite derived from other basins all over the world, the saddle dolomites of Tarim Basin have similar δ13C, δ18O and 87Sr/86Sr ratios values with those of matrix dolomite. This scenario reflects the unusual geological setting and special dolomitizing liquid of Tarim Basin. The values of δ18O, δ13C and 87Sr/86Sr ratios of calcite also can be sorted out two groups, which may been resulted from the one stage of extensive uplift of Tarim Basin from Mesozoic to Cenozoic. Fluid inclusion microthermometry data of the diagenetic mineral indicates that matrix dolomite has relatively low homogenization temperatures (Th) of 80～105oC and salinities of 12.3％ (wt% NaCl equivalent); saddle dolomite has highest Th values, which concentrate in 120～160oC and salinities of 13.5～23.7％ (wt% NaCl equivalent); quartz has relatively low Th of 135～155oC and salinities of 17.8～22.5％ (wt% NaCl equivalent); calcite has relatively low Th of 121～159.5oC and salinities of 1.4～17.5％ (wt% NaCl equivalent). These data suggest that the saddle dolomites could have formed in thermal brine fluids. Based on comprehensive petrographical study, detailed geochemistry and fluid inclusion microthermometry analysis on Lower Paleozoic dolomite of Tarim Basin, three types of dolomitisation mechanism are proposed: Penecontemporaneous dolomitisation (Sabkha dolomitisation & Reflux dolomitisation); Burial dolomitisation (shallow-intermediate burial dolomitisation & Deep burial dolomitisation ); Hydrothermal cannibalized dolomitisation. In view of host-specified occurrences of hydrothermal dolomite, the low abundance of saddle dolomite and high geochemical similarities between saddle dolomite and host dolomite, as well as highest Th and high salinities , the hydrothermal dolomite in Tarim Basin is thus unique, which could have been precipitated in modified fluid in the host dolomite through intraformational thermal fluid cannibalization of Mg ions from the host. This scenario is different from the cases that large scale dolomitizing fluid migration took place along the fluid pathways where abundant saddle dolomite precipitated. Detailed observations on 180 petrographic and 60 casting thin sections show original pores in Lower Paleozoic dolomite were almost died out by complicated diagenetic process after a long time geologic evolution. On the other hand, deep-buried dolomite reservoirs is formed by tectonic and hydrothermal reforming on initial dolomites. Therefore, the distribution of structure-controlled hydrothermal dolomite reservoirs is predicted in Tabei and Tazhong Area of Tarim Basin based on the geophysical data.

华南埃迪卡拉纪末期硅质岩和深海的氧化还原状态

A suit of cherts deposited in deep-ocean basin of South China during terminal Ediacaran and the beginning of Early Cambrian (about 550～540Ma). The origin of these cherts are controversial, and contrary standpoints exist for the redox state of the terminal Ediacaran deep-ocean because of poor study. In this paper, a detailed sedimentology, element and stable isotope geochemistry study were conducted for cherts of Liuchapo Formation in Anhua County, Hunan Province, Laobao Formation in Sanjiang County, Guangxi Province, and Piyuancun Formation in Xiuning County, Anhui Province. Some conclusions were drawn: (1) These cherts were mainly formed through chemical deposition of dissolved silica derived from chemical weathering in continent. Biological processes played a part in the cherts formation, however, the influence of hydrothermal fluids and detritus materials were trivial. (2) The terminal Ediacaran deep-ocean was anoxic and gradually oxidized. (3) Intense bacterial sulfate reduction decreased sulfate concentration in the ocean and the water column became euxinic during Ediacaran-Cambrian transition period. (4) Due to a high CO2 concentration in the terminal Ediacaran atmosphere, chemical weathering in continent dramatically increased and huge amounts of nutrimental material were transferred into ocean. The biota bloomed because of the nutrimental material. Degradation of huge amounts of organic matter maintained dissolved organic carbon reservoir in the ocean, and prolonged the deep-ocean anoxia.

塔里木盆地柯坪-巴楚露头区白云岩成岩作用机理研究

Through field outcrop dolomite observation, laboratory petrography (macroscopy, microscopy, cathodeluminescence and scan electronic microscopy), geochemistry (carbon-oxygen-strontium isotopes and trace elements) and fluid inclusion microthermometry study in Keping-Bachu area of Tarim Basin, it can be inferred that there are existing eight dolomite texture types within four evolution phases in Keping-Bachu area of Tarim Basin. The paragenesis of different dolomite texture types and associated minerals in Keping-Bachu area has been established. The carbon and oxygen isotopes of saddle dolomites and matrix dolomites overlap greatly. The Strontium isotopes results of Keping-Bachu outcrop area show that the strontium isotopes differentiation of the matrix and saddle dolomites is not obvious, the reason of which is that there is thousands of Cambrian-Ordovician dolomite strata below the stratum bearing the saddle dolomite. In the process of the heat flow upward migration, the isotopes of the heat interacts with the host rock, which leads to the similarity betwwen the strontium of the saddle dolomite and matrix dolomite. The strontium isotope of the saddle dolomite is not very radiogenic. the six types samples within four phases in the study area show Eu negatively. Comparing to the other types of samples, the δEu of saddle dolomite is relatively high falling into the range of 0.510-0.874, which shows that the saddle dolomite forms in the hydrothermal setting and is affected by the hydrothermal activity to some extend.The Lan/Ybn of saddle dolomite is high up to 15.726, which means that the HREE is very rich. It belongs to the typical hydrothermal genesis model. The δCe of saddle dolomite is positive anomaly, which is the result of high effect from the land source debris. The homogeneous temperature of the saddle dolomite falls into two ranges 110-120℃ and 125-160℃, after pressure correction, they are 141-152℃，157.5-196℃, the salinity of the saddle dolomite can reach to 20-25%. With the comparing with the burial history, the Th of the saddle dolomite is high than the ambient strata temperature, these data show that the saddle dolomite is of hydrothermal origin. The evolution trend of different dolomite and associated minerals is from matrix dolomite, dolomite cementation, saddle dolomite, quartz to calcite. Alonging with this evolution trend, the temperature of the diagenetic flow initiated from 80-100℃, after rising to 135-160℃, then gradually declined. Finally, a structurally-controlled dolomitization model is established in Keping-Bachu area of Tarim Basin.