Outcrops Of Igneous Rocks Research Articles

Spatio-seasonal patterns and sources of major ions in the Longjiang River catchment, Southern China.

River water quality is closely related to the major ion sources and hydrological conditions. However, there is a limited cognition about the geochemical sources and the seasonal variations of major ions. Thus, in this study, a total of 90 water samples were collected from the Longjiang River and its three tributaries in the dry and wet seasons. The samples were analyzed, including major ion concentrations and physicochemical parameters. Statistical analysis, such as correlation analysis and principal component analysis (PCA), was employed to investigate the spatial and seasonal variations in major ion composition and their respective sources. Our study revealed that the predominant major ions in the studied samples are Ca2+, Mg2+, HCO - 3, and SO2 - 4. Most of ions exhibited notable spatial disparities attributable to variations in geological settings and human activities. Regions characterized by igneous rock outcrops tend to exhibit higher levels of K+ and Na+, while areas with higher population densities in the middle and downstream segments show elevated concentrations of Cl-, NO - 3, SO2 - 4, Na+, and K+. The observed peak SO2 - 4 levels may be attributed to active mining operations. Most parameters displayed higher values in flood season than those in dry season due to dilution effects. Stoichiometric analysis indicated that carbonate weathering inputs contribute to over 85% of the mean total cation concentrations in the water, followed by contributions from silicates, atmospheric deposition, and anthropogenic inputs. On the whole, although the water quality remains non-polluted and is suitable for drinking and irrigation purposes, the enrichment of SO2 - 4 and NO - 3 may contribute to water eutrophication. Caution is warranted during the dry season due to reduced water flow resulting from dam interceptions and limited dilution capacity, potentially leading to elevated pollutant concentrations. Taken together, our results provided a scientific basis for water quality managements of monsoon rivers.

Isotopic range of bioavailable strontium on the Peloponnese peninsula, Greece: A multi-proxy approach

Sr isotopes are a powerful tool used for provenancing in many disciplines, but their successful application requires the availability of robust Sr baselines of potential target areas. This study presents 87Sr/86Sr signatures and Sr concentrations of water, plants and soil leachates from the Peloponnese peninsula, Greece, to establish the first comprehensive bioavailable Sr isotope baseline for this region. Additionally, this study aims to evaluate which proxy is most suitable to characterise bioavailable Sr in a geologically complex area also exposed to foreign aeolian Sr sources. Our recorded bioavailable Sr isotope signatures correspond well with the surface lithologies characteristic of the Peloponnese. Unradiogenic 87Sr/86Sr ratios and a narrow isotope range (0.70779–0.70955) characterise the bioavailable Sr signatures of the sedimentary deposits and more radiogenic and isotopically variable values (0.70791–0.72370) were measured for metamorphic and igneous rock outcrops. The differences in 87Sr/86Sr values measured between proxies of one site are comparatively low for samples from the sedimentary and igneous deposits, while the overall spread in 87Sr/86Sr values is wider for samples from metamorphic deposits. We propose to define bioavailable 87Sr/86Sr baseline ranges as the average bioavailable 87Sr/86Sr ratio of all proxies of each lithology ± its double standard deviation (x̅ ± 2σ). This results in narrow baselines for the sedimentary outcrops of 0.70832 ± 0.00053 (n = 58) for clastic sediments and 0.70835 ± 0.00089 (n = 29) for chemical sediments. The metamorphic deposits are characterised by wider bioavailable 87Sr/86Sr baselines of 0.70906 ± 0.00116 (n = 4) and 0.71429 ± 0.01133 (n = 13) for marble and schist, respectively. The bioavailable Sr baseline for igneous rock outcrops is also characterised by a comparatively wide range with 0.70950 ± 0.00259 (n = 7). The wide range in inter- and intra-site specific bioavailable 87Sr/86Sr variation observed in this study emphasise the need for comprehensive multi-proxy sampling strategies within geologically-complex areas.

The Nature of the Protolith of the Quartz—Carbonate—Dickite Metasomatites from the Bodrak and Alma Rivers Watershed and from the Trudolyubovka Area (Southwestern Crimea)

At least two outcrops of igneous rocks have been reported from the watershed of the Bodrak and Alma Rivers (southwestern Crimea). Previous studies suggested that these outcrops are composed of pre-Middle Jurassic intermediate and acidic tuffs and lavas. We compared the rocks from one of these outcrops with those from the near-contact area of the Middle Jurassic Dzhidair intrusion, which is exposed proximally, near the Trudolyubovka village. The Dzhidair intrusion is mostly composed of altered dolerites. We show that the rocks from both locations were significantly altered to quartz—carbonate—dickite metasomatites due to acidic metasomatism. The pattern of alterations and the appearance of the least altered samples of dolerites are similar across both locations.

К экологии редких степных видов рода Iris на Южном Урале

The research presents the experience of assessing the diversity of communities and ecology of 3 rare steppe species of the genus Iris L. in the Southern Urals: I. pumila L., I. scariosa Willd. ex Link and I. humilis Georgi which are distributed in the steppe and forest-steppe zones of the region and listed in the Red Data Book of Bashkortostan Republic (Krasnaya kniga…, 2011) and the Russian Federation (Krasnaya kniga…, 2008). We analyzed the ecology of communities with participation of rare species using indirect ordination, which makes it possible to identify important ecological patterns of species distribution and to give an ecological interpretation of syntaxonomic units. Totally, we collected 28 geobotanical releves within the studied coenopopulations in the Southern Urals (mainly, in the Urals and Transurals of the Republic of Bashkortostan, as well as adjacent areas of Chelyabinsk and Orenburg regions) to characterize the phytocenotic localization and ecology of rare steppe species of the genus Iris. Localities of the studied species are presented on the map (See Fig. 1). The size of the releves was 64-100 m2. Releves descriptions and classification were performed using the Braun-Blanquet approach (Westhoff and van der Maarel, 1978; Braun-Blanquet, 1964). The names of vascular plants species are given according to Cherepanov (1995). The impact assessment of complex environmental factor gradients was performed using DCA-ordination in the CANOCO 4.5 program (Ter Braak and Smilauer, 2002). DN Tsyganov’s scale which was adjusted for the Southern Urals region (Shirokikh and Zverev, 2012) was applied to estimate the environmental factors of habitats. The weighted average of environmental factors was calculated in the IBIS software (Zverev, 2007). We revealed that the phytocenosis with participation of rare steppe irises in the Southern Urals belongs to the class Festuco-Brometea Br.-Bl. et Tuxen ex Soo 1947, which unites the steppe vegetation of Southern Ukraine and Russia and includes 5 associations and 2 communities. I. pumila grows mainly on the steppe slopes of various expositions as part of the steppes of association Astragalo austriacae-Stipetum pulcherrimae Martynenko et al. 2018, which is a zonal type of the Pre-Ural steppe of the Republic of Bashkortostan. I. pumila also grows in the communities of the association Scorzonerо austriacaе-Stipetum lessingianae Yamalov 2011 prov., which is steppes with dominating Stipa lessingiana of the southern regions of Bashkortostan and in the basal community Stipa capillata [Festuco-Brometea] combining low-degraded steppe pastures, which are distributed mainly in the upland and slope habitats of the southern expositions. Among the rarest communities with participation of I. рumila, there are phytocoenoses of shrub steppes of association Spiraeo hypericifoliaе-Amygdaletum nanae Solomeshch et al. 1994, which are distributed mainly across the eastern and southeastern slopes of the ranges on stony substrates. I. scariosa was found in the phytocoenosis of the association Silene altaici-Elytrigietum pruiniferae Yamalov 2018 prov., characteristic of outcrops of igneous rocks on thermophilic slopes. Occasionally, I. scariosa is observed in the communities of Festuca pseudovina [ Helictotricho- Stipetalia], distributed to the flattened mountain slopes. Communities with I. humilis occur in the Southern Urals quite rarely and belong, according to their floristic composition, to the association Diantho acicularis-Orostachetum spinosae Schubert et al. 1981. The floristic composition of all noted communities is characterized by a high role of petrophytic species (Artemisia marshalliana, Astragalus helmii, Centaurea turgaica, Ephedra distachya, Hedysarum argyrophyllum, Koeleria sclerophylla, Orostachys spinosa, Tanacetum kittaryanum Thymus guberlinensis etc.). DCA-ordination of communities with participation of steppe species of the genus Iris showed that they are well separated in the space of the first two axes (See Fig. 2). The main axis is interpreted as a complex gradient of moisture-salinity variability. The second axis can be interpreted as the aridity-humidity gradient. The studied species of the genus Iris are plants of open habitats (steppes, meadows, river banks), therefore the lighting conditions (Lc) are critical for them (See Fig. 3-5). The critically important environmental factors also include the variability of moisture (fH) and the severity of the winter period (Cr). The low ecological amplitude of I. pumila and I. scariosa for a number of climatogenic environmental factors, such as aridity-humidity (Om) and associated soil moisture (Hd), and the amount of incoming heat (Tm) causes their confinement mainly to the steppe zone of the region. At the same time, the values of the continentality of climate factors (Kn) are in wider boundaries, especially for I. scariosa. Ordination analysis showed that, according to a complex of environmental factors, each species of the genus Iris occupies its own ecological niche. Therefore, in nature, the studied species are extremely rare in the same habitats and communities. According to the given values of ecological factors of the environment (See Table), I. pumila, I. scariosa and I. humilis in the Southern Urals have a rather narrow ecological amplitude, i.e. they are stenotopes, which largely determines their natural rarity in the region of the Southern Urals.

The nature of the protolith of the quartz-carbonate-dickite metasomatites from the Bodrak and Alma rivers watershed, and from the Trudolyubovka area (south-western Crimea)

At least two outcrops of igneous rocks have been reported from the watershed of the Bodrak and Alma rivers (south-western Crimea). Previous studies suggested that these are intermediate to acidic volcanic rocks of pre-Middle Jurassic age. We compared the rocks from one of these outcrops with those from the near-contact area of the Middle Jurassic Dzhidairskiy intrusion, which is located proximally and predominantly consists of mainly of altered dolerites. It was determined found that the rocks from both locations were significantly altered as a result of the processes of acid metasomatism, down to quartz-carbonate-dikkite metasomatites. In this case, the nature of the changes and the appearance features of relatively unaffected by this metasomatism samples the most unaltered samples represented by altered dolerites are of the same type in both locations.

Distribution of igneous rocks in China revealed by aeromagnetic data

After several decades of aeromagnetic surveys, the measured data now cover nearly the entire Chinese continent and part of the China Sea. These data were first applied in this research and could provide important insights into the distribution of igneous rocks beneath the earth’s surface. Because different types of igneous rocks have a magnetic difference and produce distinct aeromagnetic anomalies on aeromagnetic ΔT image with reduction to the pole or other data calculating maps. By analyzing more than 240 thousand magnetic susceptibility data points and aeromagnetic anomalies of known igneous rocks in the Chinese continent, it was determined that mafic-ultramafic rocks commonly have a high magnetic susceptibility and cause linear and strong positive aeromagnetic anomalies. Intermediate-felsic rocks have a stable and low magnetic susceptibility and show a flat gradient variation and regular shape. Volcanic rocks have large variability in regard to magnetic susceptibility and romance; therefore, the aeromagnetic anomalies are always random or show variation within a planar area and decrease rapidly when an upward continuation is applied. Following the aeromagnetic data and calculating the maps of the vertical first order derivative and the tilt derivative, and combining this information with known outcrops of igneous rocks, we renewed the boundaries of 82 known mafic-ultramafic rocks, 228 known intermediate-felsic rocks and 131 known volcanic rocks. In addition, we newly mapped concealed igneous rocks of 203 mafic-ultramafic rocks, 2322 intermediate-felsic rocks and 494 volcanic rocks. The igneous rocks can be identified as nine ultra-mafic belts, 10 mafic belts (or regions), 27 intermediate-felsic belts and eight volcanic blocks. The results indicate that the mafic-ultramafic rocks are mainly distributed in Tibet, Erenhot of Inner Mongolia and northern Qilian and the smaller zones in the western Kunlun, Tianshan, western Junggar, eastern Tibet, Maqin in Gansu and the Ailao Mountain (Mtn.) areas. The mafic rocks are mostly outcropped in northern Tibet, southwestern Sanjiang, Kangdian in Sichuan, Baise and Rongjiang in Guangxi, Yinjiang in Guizhou, Dabashan Mtn., Southern Dabie Mtn, Bangbu in Anhui, Qiemo in Xinjiang. The intermediate-felsic rocks are mainly located in the orogenic system and rarely within the craton. Volcanic rocks are widely developed in eastern and western China such as the circumference of Songliao Basin, Erlian Basin, the southern Yellow Sea - Subei Basin, Bohai Bay Basin, eastern Zhejiang, the circumference of Hainan Island, southern Sichuan - northern Yunan, central Tibet, the Bachu area in Tarim Basin, Junggar Basin and Turpan-Hami Basin.

Barium content of paleosols from Central Italy

A paper published in 2013 concerning the elemental composition of 50 paleosols from Central Italy (Tuscany and Abruzzo) noted that Barium values were exceptionally high, a fact which could be not justified by the presence of neighbouring outcrops of igneous rocks. This current paper aims to explain the origin and significance of barium enrichment in these Pleistocene paleosols (Xerults, Xeralfs, Udalfs and Xerepts) formed on alluvial siliciclastic deposits mainly derived from sandstones and shales and, in a few cases, insoluble residues of Mesozoic carbonate rocks. Ba content was considered in relation to the molecular weathering ratio, soil pH and total Mg content. A qualitative inverse correlation was suggested between Mg and Ba for most soils. Maximum Ba values were found both in acid and alkaline soils, while minimum values were observed in neutral soils. This suggests the existence of different pedoclimatic environments. The acid soil solution supports the Ba release from minerals and soil components and its precipitation in the presence of SO<sub>4</sub><sup>2-</sup>, clays and Fe/Mn nodules, whereas other bases are removed. In contrast, the soils during seasonal low humidity periods or extended events of drought have a different pH: the soil solution then has a higher base concentration and therefore a greater likelihood of Ba precipitation bound to clays, metal oxides or even as insoluble sulphate (barite). Thus the soils with higher and lower pH are enriched in Ba both directly and indirectly in relation to ionic strength of the soil solution. The significant enrichment in Ba is ascribed to intense and very long pedogenetic processes during past climatic conditions of a wet- warm subtropical type, which acted on the Italian paleosols of Pleistocene age. The recurring shrink-swell pattern would have increased the rate of chemical weathering, the rate of barium release in the soil solution and its subsequent immobilisation in neoformed complexes as barite and others.

The field description of igneous rocks

Field Techniques. Description of Igneous Rock Outcrops. Hand Specimens and Their Interpretation. Mode of Occurrence of Igneous Bodies. Volcanic Rocks. Minor Intrusions. Plutonic Rocks I: The Calc-Alkaline Association. Plutonic Rocks II: The Alkaline Association. Plutonic Rocks III: Mafic-Ultramafic Associations. Plutonic Rocks IV: Anorthositic Associations and Charnockitic Associations. Metamorphism. Appendix. References and Further Reading. Index.

SHRIMP U–Pb zircon dating of the Katerina Ring Complex: Insights into the temporal sequence of Ediacaran calc-alkaline to peralkaline magmatism in southern Sinai, Egypt

SHRIMP U–Pb dating reveals that the hypabyssal Katerina Ring Complex formed over a ~9Ma interval. The first rocks that formed were the alkaline to peralkaline granitoids that form the wall and the roof cap of the Ring Dike, emplaced at 602±8Ma and 602±4Ma respectively. These were closely followed by the Isbaiya calc-alkaline quartz-monzonites at 599±3Ma, and by the main Katerina pluton at 596±3Ma. The pluton is composed of A-type metaluminous fluorite-bearing granites that contain one inherited Archean zircon (~3.2Ga). The Katerina magmatic cycle ended with the intrusion of another peralkaline body in the ring interior at 593±2Ma; this body forms the summit of Gebel Musa (Mount Sinai). The Ring Dike encloses older rocks such as the 844±4Ma Moneiga quartz-diorites and the 622±3Ma Rutig volcanic rocks. The conglomerates interbedded with these contain boulders of granites with ages of 735±6Ma and 748±11Ma. Outcrops of igneous rocks with these ages are currently unknown in the Sinai, probably because they were recycled into the late ~590–625Ma granites and volcanic rocks, as is revealed by zircon inheritance. The alternating formation of calc-alkaline and alkaline granite magmas during the short time frame of the Katerina magmatic cycle (~9Ma) poses the problem to understand which mechanisms have controlled the production of coeval calc-alkaline and alkaline magmas, the magma sources of which remain poorly constrained as identical Sr and Nd isotope compositions cannot distinguish between mantle melting and reworking of juvenile crust. Additionally, the diachronism of peralkaline magmas from the Katerina magmatic cycle with respect to other areas of the Sinai suggests that the magmatic focus migrated in space and time which may be related to alkaline metasomatism processes in the crust.

New, high resolution swath bathymetry of Gettysburg and Ormonde Seamounts (Gorringe Bank, eastern Atlantic) and first geological results

High resolution swath bathymetry of shallow water (< 200 m) oceanic seamounts is a relatively rare issue. During the recent Gorringe_2003 cruise over the Gorringe Bank (Eastern Atlantic) we collected multibeam bathymetry on the bank’s two shallow summits, Gettysburg and Ormonde in the –25/–400m depth range at a resolution rarely achieved over an oceanic seamount. We also carried out bottom samplings and ROV dives in the same bathymetric interval. The acquisition parameters and the characteristics of the echosounder employed allowed to generate a Digital Terrain Model (DTM) with metric spatial resolution upto 75–100 m depths. To ensure proper tidal corrections a tide-gauge was deployed at sea-bottom during the survey. DTM reveals for the Gettysburg Seamount an almost perfectly circular summit resulting from the blanket of bioclastic sediments over an igneous ‘core’ consisting of sheared and foliated serpentinites. The core is dissecated by N 10° W trending ridges elevating some tens of metres and filled in between by bioclastic sands. Both foliation and ridge patterns seem related to primary igneous fabric rather than later structural deformation. The overall circular shape confirms the origin of the seamount as a mantle serpentinite diapir in analogy with similar, but subduction-related, circular seamounts observed in the Bonin Trench (western Pacific). In contrast the Ormonde elongated summit follows the regional tectonic trend with a N 60° E active (seismogenic?) fault on its southeastern flank. Its basement morphology corresponds to the outcrops of igneous rocks chiefly consisting of gabbros, volcanic rocks and dyke intrusions. On both seamounts topographic profiles show that the ‘shelf’ area is somewhat convex rather than flat like that of ‘Pacific type’ guyots and is bordered by a depositional, locally erosional shelf break, located between –170 and –130 m. Various terraced surfaces and some geological evidence confirm previous observations and indicate relative sea-level oscillations with partial emersion of the two summits that seem occurred during the last glacial cycle (past 120 ka).

The geochemistry and isotopic composition of the mafic and intermediate igneous components of the Cape Granite Suite, South Africa

A number of small outcrops of igneous rocks, gabbroic to granodioritic in composition, occur scattered throughout the western Cape in South Africa. These outcrops, which are mostly intrusive into the Malmesbury metasedimentary sequence, define a small number of medium-sized plutons. A characteristic feature of the larger plutons is their composite nature. Each pluton consists of multiple intrusive phases; a few show extensive hydrothermal alteration. Plutons from Yzerfontein and Mud River, which occur in the Tygerberg terrane, are high-K calcalkaline (K-trans-alkaline) while all plutons from Malmesbury, which occurs in the Swartland terrane, are tholeiitic. The high-K suite correspond to other I-type Cape granites, whereas the tholeiitic Malmesbury plutons may be a precursor of A-type Cape granites in both the Tygerberg and Swartland terranes. Monzonite from the Yzerfontein pluton yielded a UPb age of 519±7 Ma on zircon mineral separates. Rb-Sr isotope data did not yield reliable ages, possibly due to alteration, but yielded distinct initial isotope ratios for the high-K calc-alkaline and the tholeiitic plutons. The δ 34S isotope ratios of pyrite range from 1 to 2.7% for Yzerfontein and from 3.6 to 4.6% for Mud River, suggesting a magmatic source for the pyrite. PbPb data on whole rock and pyrite samples imply crustal input into all the original magmas.

Influence of geological factors on soundness and abrasion resistance of road surface aggregates: A case study

A study has been carried out on soudness and abrasion resistance of crushed-rock aggregates used in heavily trafficked road surfacings in Gauhati, a city situated in the State of Assam, India. The crushed-rock aggregates under study were obtained from Precambrian acid igneous rock outcrops in and around Gauhati. The grain, size and the volume of pore spaces were found to be the significant geological factors influencing soundness and abrasion resistance. The durability, in terms of resistance to weathering and resistance to wear, of the acid igneous rocks was found to increase with decrreasing grain size and decreasing volume of pore spaces.

Sedimentology and Shallow Stratigraphy of Mid-Atlantic Ridge Mountain Tops: ABSTRACT

Bottom photographs and drilled rock cores, obtained from several mountain tops along the crest of the Mid-Atlantic Ridge near 45°N, show a patchy distribution of basic igneous rock outcrops and localized mixed deposits of basaltic boulders, cobbles and pebbles, ahermatypic-coral skeletal fragments, and calcareous mud. Coralline limestones repeatedly have been observed underlying unconsolidated pebble and mud deposits. Between 900 and 1,200 m water depth on the south slope of Confederation Peak (45°23^primeN, 28°10^primeW), outcrops of fractured igneous rock are surrounded by deposits of angular cobbles and pebbles in a calcareous-mud matrix. Downslope, exposed, igneous rock outcrops are surrounded by pebble deposits with about a 60% calcareous-mud matrix. A basalt conglomerate core drilled near the top of this mountain (914 m) is composed of manganese-coated pebble and cobble-sized basaltic fragments cemented by a calcareous matrix that may have lithified, in part, during subsequent vertical uplift of this deposit to its present elevation. At 1,042 m water depth, porous coralline limestone was encountered by the drill after 143 cm of penetration through unconsolidated sediments. The surfa e of the north side of Bald Mountain (45°13^primeN, 28°56^primeW) between 1,555 and 2,380 m is composed of outcrops of basic igneous rock alternating with angular cobble and gravel deposits, probably of similar composition. An intermittent cover of calcareous mud is evident starting at about 1,900 m water depth. Slightly porous and friable, coralline limestone, covered by 81 and 155 cm of coral skeletal material, basaltic pebbles, and calcareous mud has been drilled at 1,426 and 1,682, respectively. Generally, limestones covered by a relatively thin layer of unconsolidated sediment and those situated at relatively shallow water depths show a greater degree of induration. Five whole-sample radiocarbon dates determined for the upper parts of several limestone cores range approxim tely between 31,000 and 39,000 years, suggesting that deposition and (or) lithification may have been associated with a moderately warm interval following the early Wisconsin glaciation (Emiliani's Stage 3). End_of_Article - Last_Page 803------------

The Correlation of pre-Cambrian Granites by means of Heavy Mineral Analyses

The correlation of isolated outcrops of igneous rocks where two or more similar intrusions are exposed is a difficult problem which is not always solved by thin sections or field studies. Such a problem was encountered in mapping the closely related Pikes Peak and Silver Plume granites of pre-Cambrian age in the Sawatch Range of central Colorado (Fig. 1). A comparison of the heavy minerals of the isolated outcrops with those of known granites was undertaken; and for this purpose large samples, suitable for crushing and heavy mineral analysis, were collected from various points within the areas of each batholith, and from the small outcrops whose age was in question. It was hoped that sufficient similarities in the heavy mineral assemblages might be established to be of value in making correlations. Furthermore, as work on the heavy minerals in igneous rocks is still in the experimental stage, a series of analyses from various parts of a given batholith should throw some light on the question of whether heavy minerals may be distinct and constant enough to be characteristic and so give a reliable means of correlation of isolated exposures.

Alkaline Intrusives of Lutingshan and Ch'iaoshan in S. Shansi*

The known areas of alkaline rocks in Shansi are all situated in or near regions where different systems of trendlines meet. As indicated on any map of Shansi by the sudden diversion of the Fenho river towards W we should find near the bend a crossing of trendlines and it is here that the Linfen (P'ingyang) intrusives are situated. The newly discovered intrusives, which are described in this paper, are Lutingshan and Ch'iaoshan and they may be considered distant satellies of the main intrusive body Lungwangmiao (cfr. Nyström: Some alkaline rocks of Shansi province). They are both typical “shoulder” intrusives, reinforcing the edge of a limestone plateau.Lutingshan of which the highest eminence consists of Carboniferous sandstone, harbours in its S slope an almost circular stock of about 4000 m. diameter, the most striking feature of which is its topography. The rock composing this igneous body is obviously of two different kinds: the rim showing a jagged “shark's teeth” contour has offered stronger resistance to erosion, wheras the centre is deeply excavated, the whole resulting in what one may call a “pseudo‐crater”, about 200 m. deep. The rim rock is light grey banatite, inclining to akerite, and the centre a red, easily weathered alteration‐product of banatitic orgin, the alteration probably being of hydrothermal nature and having taken place during the latter stages of solidification. There are veins of pink gramte‐aplitic composition in the rim. There are highly metamorphosed inliers of limestone in die southern part of the intrusive and here a valley provides an outlet from the “crater”. There is also a narrow canyon providing exit towards SW. These topographical features are without parallel in the other alkaline areas in Shansi.The other intrusive Ch'iaoshan may be seen from Lutingshan at a distance of a few km. towards E. It looks like a dark, cone‐like eminence, rising above the rather undisturbed layers of Ordovician limestone. At closer inspection it is seen that this cone represents the northern semicircular part of a bat‐tike intrusive which spreads along a faultline running NE‐SW. It is sculptured in numerous peak, of which the northern eminence, mentioned above, is the highest. The topography suggests a variety of rocks of different hardness. Ch'iaoshan no doubt marks the spot where, through intersection of trendlines, the crust has been particularly weakened. This is also made probable by the numerous satellites which—in contrast to Lutingshan—are very prevalent round Ch'iaoshan.The high northern peak consists of a coarse crumbling pink porphyrv extremely affected by cleavage. Towards the centre of die intrusive the rock becomes more dense and firm but there are numerous miarolithic cavities. It is of light pink colour and has bisilicate crystals scattered throughout. Since this seems to be fairly representative of a large mass of the intrusive, a chemical analysis was made and the composition is strongly alkaline, but with quartz, in fact a nordmarkite and very similar to certain alkaline rocks of W Shansi. There are dykes, of a snow‐white banatite and veins of granite‐aplite, showing thus rapid differentiation both in a dioritic and in a granitic direction. The satellites are of banatitic character. Here and there grass‐green patches of epidote are seen in die outlying parts of the intrusive. No inliers of limestone have been seen.Concerning the association of rocks in these two intrusives, they show undoubted consanguineity both with each other and with the parent intrusive Lungwangmiao. From a hypothetical parent rock of akeritic composition there has been differentiation both in a granitic (aplitic) and in a dioritic (banatitic) direction. The syenitic differentiation (resulting ultimately in nepheline and nosean‐bearing rocks) so characteristic for die alkaline areas in W. Shansi, is conspicuous by its absence and there are no alkaline pyroxens (aegirine or aeg. augite) to be seen. The nordmarkite in Ch'iaoshan is an intermediary member in the granitic differentiation process.Regarding the age of the intrusions it is not possible to arrive at anv definite conclusion because of the absence of sediments, contemporaneous, or younger than die igneous action. But since the intrusions are so obviously connected with the Fenho‐Weiho graben diastrophism, which produced fault‐scarps, along which Pliocene beds are interbedded with conglomerates from the scarps and since, on exposed surfaces of the parent (Lungwangmiao) intrusive, Hipparion‐beds can be found covering outcrops of igneous rocks, it seems that until further information is forthcoming, we may in a preliminary and tentative way establish the time of intrusion to be during the closing stages of maximum diastrophism of mid‐Tertiary time.

III.—A remarkable instance of Rock Differentiation

Upon Sheet 339 (Devonshire) of the new Geological Survey maps, one instance out of the very numerous outcrops of igneous rocks thereon indicated proves to be of unusual interest by reason of its peculiar constitutional modifications in different parts of the same mass. The rockin question occurs about four and a quarter miles 15° north of west from Newton Abbot, near to the hamlet of Bickington, within the limits of a farm named Lurcombe. It is an intrusive amidst the shales and grits of the Culm, occurring almost on the junction-line between that series and the Devonian, whose massive limestones and volcanics dominate it in elevation within a quarter of a mile on the south-east.