Rocks In China Research Articles

太湖石からサズ葉文様への系譜

Saz style ornaments are known as the motifs which are formed by curvy, long, notched leaves. And the ornaments are attributed to the creation of Sah Kulu who was the Ottoman palace painter in the 16th century. Therefore Saz style ornaments have been caused for discussions in the Sah Kulu studies. Although the source and origin of the ornaments have been not studied yet.The article is aimed to present that the source of these motifs are originated from the Taihu-rocks.The Taihu-rocks which are produced in Taihu Lake in China, are very famous and popular rocks in China from ancient times and one of the favorite motifs as a happiness symbol in Chinese arts.The rocks had been introduced to Islamic World by Chinese paintings and ceramics for the first time in the Ilkhanids.The progressive forms presented from Taihu-rock motifs to Saz style ornaments are explained as the following steps;1) The first step: The realistic forms of Taihu-rocks with ‘Ling zhi’, lucky mushrooms or clouds in the forest scenes.2) The second step: Stylized Taihu-rock motifs. Plant or dragon motifs are made passing through the wholes of the Taihu-rocks.3) The third step: Taihu-rocks transformed into the lotus leaves.4) The fourth step: The formation of Saz style ornaments.It is said according to the formation of Saz style ornaments that the transformation in which rocks change into leaves, played very important role as a method for ornamentation.

Reworking intensity—A key factor leading to the formation of superlarge gold deposits in greenstone belts and metamorphosed microclastic rocks in China

The greenstone belt and metamorphosed microclastic rock-type superlarge gold deposits in China are hosted in metamorphic rocks and later intrusive bodies. Sedimentation, regional metamorphism and mineralization contributed a lot to the formation of the deposits, so did remelting magmatic process to some deposits, but the deposits were finally formed by reworking processes. The key factor leading to the formation of superlarge gold deposits is the reworking intensity, which for superlarge gold deposits is reflected by the large-scale reworked source rocks and even ore materials of various sources, strongly oxidized ore-forming fluids with a long and repeated active history and stable geothermal heat current. The factor which decides the reworking intensity is the network consisting of structures of different classes.

Migration of Some Elements and Radionuclides across a Granite‐Granite Contact Zone: A Natural Analogue for Safe Disposal of High‐Level Radwastes

Abstract Elements and natural radionuclides in the contact zone of two granites with different ages would migrate from one to the other because of the difference in their chemical contents and later water‐rock interactions. This migration could serve as an analogue for the near‐field process of radwastes in a high‐level radwaste deep geological disposal repository.In the contact between the Indosinian granite (whole‐rock Rb‐Sr isochron age at 214±3 Ma) and Hercynian granite (zircon U‐Pb isochron age at 296±31 Ma) located in Ziyuan County, Guangxi, the O and Pb isotope characteristics and the activity ratios of 234U/238U, 230Th/238U, 230Th/234U and 226Ra/230Th show that, based on the whole‐rock chemical contents, both of the two granites have maintained a relatively open chemical system in their evolution processes. However, as there is no obvious open fault, the migration of major elements, trace elements and natural U‐series nuclides takes place within only 1–2 m in the contact zone, and water‐rock interactions in the weak contact plane only affect the redistribution of chemical constituents at a distance of 30 cm.Fractures are the pathways for fluid flow. In term of uranium‐series disequilibrium and the radionuclide data (the abnormally high value of 234U/238U=4.60 in the fracture sample), significant water‐rock interactions could cause the bordering rocks to be altered and leach some radionuclides out. U and Ra migrated selectively at the time scale of 106 a and 104a, respectively, but the redistribution of granite is only within 10 cm from the contact, and Th seems to be immobile. On the other hand, clay‐enriched fillings in the fractures can adsorb most of the leached radionuclides. The adsorption could significantly retard radionuclide migration in the fractures, but its influence in distance is less than 10 cm from the fracture plane. The present data could be viewed as evidence for safety confidence for the high‐level radwaste disposal repositories hosted by granitic rocks in China.

Catalytic decarboxylation of fatty acid by iron-containing minerals in immature oil source rocks at low temperature

The catalytic activities of seven immature source rocks in China on fatty acid decarboxylation for generating hydrocarbons have been evaluated by determinating the CO2 content from decarboxylation reaction of stearic acid. It has been found that the catalytic activities of immature source rocks mainly depend on the structure type of the minerals. In general, the catalytic activities of carbonates are higher than those of clays at low temperature. The higher its iron content, the higher the catalytic activity of carbonate.

Spatial Distribution and Ages of Alkaline Intrusive Rocks in China and Related Tectonics

Abstract: On the basis of the geological data from 220 intrusions and isotope ages of 115 rock bodies, the paper discusses the distribution of 18 alkaline intrusive rock belts along deep faults and their relations to the plate tectonic activity. In view of the presence of a large amount of Variscan alkaline rocks of deep‐source character, it is inferred that mantle diapirism was very strong in China during the Variscan. Besides anorogenic and postorogenic alkaline granites, there also occur alkaline granites formed in the terminal orogenic stage when the regional tectonic activity was of compressional nature. Finally, the paper discusses the tectonic environment of the Maoniuping nordmarkite in Mianning county, Sichuan province, and the authors consider it to be a compressional environment originating after rift closing.

Cambrian explosion still in the water

Was Adrian Thomas's short note in the last issue of TREE[1]intended to be provocative? The Cambrian explosion has not been `blown out of the water'. First, the existence of late Precambrian metazoan fossils does not alter the fact that Cambrian fossils record an explosive diversification of animals, although it may make it easier to explain. Second, it has been many years since the fossil record of metazoan animals started with the Cambrian explosion—I first learned about the late Precambrian Ediacara fauna when I was an undergraduate 25 years ago and it was not particularly new to science then. The recent discovery of fossilized metazoan embryos in 570 million-year-old Precambrian rocks in China[2]is tremendously exciting, but it is not the first indication of a metazoan fossil record predating the Cambrian explosion. The Ediacara fauna (now known as Vendozoa or Vendobionta), once shoehorned into extant phyla, has been interpreted as representing an early radiation of metazoans[3]that were not closely related to Cambrian metazoan animals and that flourished during the last 60 million years (very approximately) of the Precambrian but became extinct before the Cambrian explosion. The Chinese fossil embryos may represent the oldest fossils of metazoans that were directly ancestral to Phanerozoic (Cambrian onwards) lineages. A plausible explanation has been put forward (also reported in the same issue of TREE) that the vendozoans occupied the ecological niches available to large animals (several cm), restricting Precambrian (late Proterozoic and Vendian) precursors of Phanerozoic metazoans to small size (mm) and, therefore, little chance of fossilization[4]. The Cambrian explosion can then be attributed partly to a size increase of `Phanerozoic Metazoa' once the vendozoans became extinct. In terms of the fossil record of all metazoans, the vendozoans could even predate the latest Chinese findings. Recent dating of the Ediacara fauna of the English Midlands suggests that it has a minimum age of 603±2 million years, although the authors[5]are cautious about the accuracy of this figure.

Geology and geochemistry of reworking gold deposits in intrusive rocks of China—II. Gold deposits and their genesis

Gold deposits in intrusive masses include the veinlet dissemination, quartz vein and veinlet dissemination + vein types. They are distributed in fracture zones along the endocontact zone of a batholith or in the centre and edge of a stock. The metallogenic epochs are Yenshanian, Hercynian, Archean, Proterozoic and Himalayan. The gold deposits are characterized by a big difference in time span between gold mineralization and the formation of host masses. Ore-forming materials were derived from the masses and auriferous strata and ore-forming fluids came from meteoric and formation waters. When circulating water was heated by ascending heat flow, gold would be extracted, concentrated and transported from auriferous rocks and then precipitated in the masses during the late tectonic movement. Finally gold deposits were formed in the intrusive masses.

Geology and geochemistry of reworking gold deposits in intrusive rocks of China—I. Features of the intrusive rocks

Most gold deposits in intrusive rocks were formed as a result of reworking processes. The intrusive rocks containing gold deposits and consisting of ultramafic-mafic, intermediateacid and alkaline rocks of the Archean, Proterozoic, Caledonian, Hercynian and Yenshanian periods occur in cratons, activated zones of cratons and fold belts. Among them, ultramaficmafic rocks, diorite, alkaline rocks, and anorthosite are products of remelting in the mantle or mantle-crust or mantle with crustal contamination. However, auriferous intermediate-acid rocks are products of metasomatic-remelting in auriferous volcanic rocks or auriferous volcanosedimentary rocks in the deep crust.

Characterization and origin types of immature and low-mature amorphous kerogen in terrestrial source rocks

The microfluorescent technique was applied to investigate the fluorescence alteration patterns of amorphous kerogen of the terrestrial source rocks of China. Two fluorescence parameters, I54620 andR were suggested, which can be taken to divide the amorphous kerogen into five types: algae amorphinite, biodegraded amorphinite A, B, C, and humic amorphous. On the basis of this, the Rock-Eval analysis results of source rocks were used to investigate the hydrocarbon generating potential of these amorphinite.

Fossilized Metazoan Embryos from the Earliest Cambrian

Small globular fossils known as Olivooides and Markuelia from basal Cambrian rocks in China and Siberia, respectively, contain directly developing embryos of metazoans. Fossilization is due to early diagenetic phosphatization. A nearly full developmental sequence of Olivooides can be observed, from late embryonic stages still within an egg membrane, to hatched specimens belonging to several ontogenetic stages. Earlier cleavage stages also occur, but cannot be identified to taxon. Olivooides shows similarities to coronate scyphozoans and to their probable Paleozoic representatives, the conulariids. Markuelia eggs contain looped embryos of a segmented worm with short, conical processes covering the body.

REE geochemistry of some alkali-rich intrusive rocks in China

Based on the REE analyses of about 300 samples from 40 alkali-rich intrusive rocks, a systematic study on the features of REE composition was made, and the major factors controlling the REE distribution are discussed. According to REE, trace elements composition and Sr, Nd isotopic characteristics, the source materials and petrogenetic process of the alkali-rich intrusive rocks were studied. The petrogenetic models of Zijinshan, Sairna, Nianzishan and Shanhaiguan alkali-rich intrusive rocks were calculated using multisequence fractional crystallization and assimilation fractional crystallization models.

Tectonic environments of Cenozoic volcanic rocks in China and characteristics of the source regions in the mantle

Extensive volcanism is one of the important features of Cenozoic geology in China. Based on temporal-spatial distribution, the volcanism was associated with three major different geological settings: 1) the continental rift basalts in Northeast and North China; 2) the tension-fault basalts on the continental margins of Southeast China; and 3) the collision-zone high-K volcanics in the Qinghai-Xizang Plateau and its vicinities. The characteristics of “depletion in the south and enrichment in the north” of the China continental mantle are strongly supported by isotopic evidence. The Cenozoic continental mantle of China can be divided, on the basis of isotopic evidence and regionally geological characters, into the following geochemical provinces: 1) the depleted mantle in South China; 2) the primary mantle in Northeast and North China; 3) the hybrid and transitional mantle in the region of Shandong, Anhui, Jiangsu and northern Zhejiang; 4) the depleted mantle around the Bohai Bay and the Lower Liaohe River; 5) the K-metasomatic enriched mantle in the northern part of Northeast China; and 6) the re-cycled enriched mantle in the ancient subduction zone in the Qinghai-Xizang Plateau and its surroundings. These geochemical characteristics on a regional scale must be a reflection of the nature of lithosphere evolution.

Ultra-high-pressure metamorphic rocks in China

Ultra-high-pressure metamorphic rocks in China

Cretaceous conchostracan faunas of China

Eight conchostracan faunas are known from the Cretaceous rocks in China. They are the Early Cretaceous Orthestheria and Late Cretaceous Aglestheria faunas from the south-west China biogeographic province, the Early Cretaceous Yanjiestheria fauna from the north and southeast China provinces, the Late Cretaceous Linhaiella and Tenuestheria faunas of southeastern China, and the Euestherites and Daxingestheria faunas of northeastern China. The Nemestheria fauna is widely distributed in mid-Cretaceous strata in most regions of China.

Nonmarine Cretaceous bivalve assemblages in China

Bivalve fossils are very abundant in nonmarine Cretaceous rocks in China. Six assemblages are documented: Nakamuranaia-Margaritifera ( Mengyinaia)- Neomiodonoides and Peregrinoconcha-Koreanaia-Pseudohyrioides (Berriasian-Barremian); Trigonioides (T.)-Plicatounio (P.)-Nippononaia (N.) (Aptian-Albian); Plicatounio (P.?)-Maninsonella-Kwanmonia (?) and Trigonioides (Hoffetrigonia)-Trigonioides (Kumamotio?)-Plicatounio (P.) (Cenomanian Santonian); and Pseudohyria-Sainshandia Limnocyrena (Campanian-Maastrichtian). During the Early Cretaceous there appears to have been provincialism of these assemblages, notably the second-named assemblage which is limited to the extreme southwest of China.

Petrochemistry and Sr, Pb, and Nd isotopic geochemistry of early precambrian rocks, Wutaishan and Taihangshan areas, China

Abstract In the Wutaishan and Taihangshan region, China, the lowermost high-grade metamorphic complex of grey-gneiss and amphibolite, the Fuping Complex, gives a 2.2 ± 0.2 Ga Pb-Pb isochron age with a first stage growth μ = 7.73, and a 2.37 ± 0.07 Ga SmNd isochron age with (143Nd/144Nd)0 = 0.50963 ± 0.00005 or ϵNd(T) = 1.50. Nd-depleted mantle model dates (TDM) of amhibolites 2.48 to 2.60 Ga, those of gneisses are 2.43 to 2.46 Ga. The unconformably overlying medium- to low-grade metavolcanic complex, the Wutai Complex, gives a 2.0 ± 0.1 Ga RbSr isochron age with (87/86Sr) 0 = 0.7025 ± 2, a 2.27 ± 0.02 Ga PbPb isochron date with afirst stage growth μ = 7.73, and a 2.26 ± 0.06 Ga SmNd isochron first stage (143Nd/144Nd)0 = 0.5097±2 orϵNd(T)=1.08. Individual sample Nd depleted mantle model date are ∼ 2.5 Ga. Metavolcanic samples from low-grade metasedimentary rocks of the Hutuo Group all lie close to a 2.3 Ga reference line on a RbSr isochron plot, have Nd TDM = 2.32, 2.34, and 2.62 Ga. From previous geological work, published UPb zircon dating, and ourisotopic and geochemical results, we infer that the Fuping rocks formed ∼ 2.6 Ga ago in an environment like a modern island arc. The Wutai Complex formed by 2.5 Ga ago, mostly formed in a tectonic setting similar to that of the Fuping Complex, with the exception that one volcanic cycle formed in an environment like a modern MOR and one unit formed in an environment transitional between modern within-plate and plate margin settings. The Hutuo Group formed 2.4 Ga ago in a within-plate tectonic environment. There is no evidence for continental crust before 2.6 Ga in the Wutaishan and Taihangshan region. This contradicts previous assignment of the Fuping Complex to 2.8 Ga ol older. The Fuping Complex is not an early nucleus of the Sino-Korean Craton. The new data also confirm that the Wutai Complex is older than its original assignment as Early Proterozoic. The SmNd systems for metabasaltic rocks in the region, either in amphibolite facies or in greenschist facies, are all significantly disturbed, in contrast with the undisturbed SmNd reported in previous studies of the Sino-Korea Craton. This study provides further evidence that the Archean igneous rocks in China formed at different times, from heterogeneous and depleted mantle sources.

Evidence for intracontinental thrust-related exhumation of the ultra-high-pressure rocks in China

Coesite- and diamond-bearing ultra-high-pressure metamorphic rocks produced during the Triassic continental collision between the Sino-Korean and Yangtze plates are offset by about 530 km along the sinistral Tanlu fault in eastern China. The Tanlu fault terminates abruptly south of the ultra-high-pressure metamorphic terrain in Dabie Shan and does not extend into the foreland fold belt along the Yangtze River. This suggests that in this region the Mesozoic major sinistral displacement along the Tanlu fault was transferred to southward- directed thrusting, which led to the exhumation of the ultra-high-pressure metamorphic rocks formed earlier. Postcollisional Himalayan-type intracontinental thrusting and concomitant erosion appear to be the main agents in the exhumation of the very high pressure metamorphic rocks in China.

Spectral reflectance of recently fallen chondrites and some igneous rocks in China

Polarization and radiation measurements and microwave studies show that the planets and the great majority of asteroids in the solar system are covered by soils similar to regolith on the moon surface. The soils repesent the composition of the asteroids and the geological elements of the planets. The spectral reflectance shows a tendency of decreasing from near ultraviolet, visible to near-infrared in order of LL → L → H → E with increasing Fe0/Fet rato and toward to absorption for Jilin. Xinyang and Zaoyang ordinary chondrites and Qinzhen enstatite chondrite recently fallen in China. The same chemical group of meteorites feature deeper absorption valleys with increasing metamorphic grade. The spectral reflectance of igneous rocks varies from strong to what is like that of H-group chondrites in order of acid → basic → ultrabasic rocks.

Eastern Asia and the Western Pacific timing and spatial distribution of rifting in China

A compilation of recognized rifts in China indicates that five distinct episodes of rifting have occurred. These episodes occurred at approximately 2.3 Ga, 1.85−1.7 Ga, 1.0-0.7 Ga, 550−190 Ma, and 175 Ma to present. The timing and location of rifting has largely been a function of tectonic activity along the margins of the various Chinese paleocontinents. Some of the oldest rocks in China are found in the Sino- Korean and Tarim cratons, and most of the identified Precambrian rifts are found within or on the margins of these cratons. These cratons are viewed as the continental nucleus of China, and fold belts and microcontinents have been accreted to this nucleus through time. Much of the locus of rifting has migrated away from this nucleus as has the location of the continental margin—especially in the Paleozoic. Beginning in the Middle Mesozoic, rifting commenced along the entire eastern margin of China. Extension occurred concomitantly with subduction in a backarc setting; this is the dominant Cenozoic extensional regime in China and is still active today. To date, few Cenozoic rifts have been , found in western China where most tectonism is probably a consequence of the collision between India and China, but it seems likely that more rifts will be discovered in this area as it becomes better studied.

Determination of trace elements in crude oils and organic materials extracted from oil-forming source rocks in China by INAA

A combination of Soxhlet extraction, column chromatography and INAA with GC and GC-MS was used in this work for the study of the abundance patterns of 36 trace elements and their correlation in nearly 100 samples of crude oil and organic materials extracted from oil-forming source rocks from 10 main Chinese oilfields. The low V/Ni ratios of 0.01 to 0.3 state the oil-forming continent environment. The geochemical significance hinted from other trace element abundances is also briefly discussed.