The palingenic calc-alkaline granitoid massifs of the Olekminsky complex form a magmatic belt stretching within the Western-Stanovoy terrane in the northeastern direction for more than 700 km. New U-Pb LA-ICP-MS dates for zircons from the granodiorites of the Marekta-Bereinsky massif of the Olekminsky complex and the granodiorites of the Yamninsky massif of the Krestovsky complex were obtained, amounting to 371±4 Ma and 364±5 Ma, respectively. These geochronological data are well consistent with the 355–358 Ma ones, therefore suggesting the Late Carboniferous age of quartz-diorite-granodiorite-granite rocks of the Olekminsky complex. However, these dates are not correlated with the existing legends of geological maps covering the area of the Western-Stanovoy structural-formation zone or the Western-Stanovoy terrane, as the intrusive formations of the Olekminsky complex are dated as the Early Paleozoic. In addition, new geochronological data call into question distinguishing of a separate Early Paleozoic Krestovsky granitoid complex.

The geodynamic evolution during the closure of the Paleo-Tethys Ocean in the Tibetan Plateau remains to be fully understood. The Longmu Co-Shuanghu suture zone in the northern Tibetan Plateau has usually been considered to represent the main ocean basin of the Paleo-Tethys Ocean, so it plays a key role in understanding the evolution of the Paleo-Tethys Ocean. In this study, we focused on the Gacuo and Bensong batholiths on the north and south sides of the Longmu Co-Shuanghu suture zone, respectively. We conducted detailed zircon geochronology and whole-rock geochemical and Sr -Nd isotopic analyses, as well as zircon Hf isotope studies. Zircon U -Pb dating indicates that the Gacuo batholith was formed ca. 223-209 Ma, and the age of the Bensong batholith is ca. 213- 203 Ma. The Gacuo batholith is mainly composed of I -type granitoids, which are most likely attributed to partial melting of ancient sedimentary materials of the North Qiangtang terrane with a mixture of similar to 0%-30% amounts of mantle-derived components. In contrast, the Bensong batholith has granitoids of A -type affinity, and it was probably generated by partial melting of Mesoproterozoic crust of the South Qiangtang terrane with limited mantle contribution ( < 5%). Finally, we suggest that the Gacuo batholith was probably generated by the break -off of the oceanic slab beneath the North Qiangtang terrane, while the Bensong batholith was related to a possible lithospheric delamination process of the South Qiangtang terrane after continental collision. Therefore, the Gacuo and Bensong batholiths both developed in a postcollisional tectonic setting, and they recorded the evolutionary process of the subduction and closure of the PaleoTethys Ocean during the Late Triassic.

The Eastern Pontide Orogenic Belt (EPOB), a well-preserved palaeo-magmatic arc, exists south of the Black Sea, from Bulgaria to Georgia. The region, which forms an essential part of the Alpine-Himalayan belt, contains volcanic rocks formed in the Late Cretaceous. This paper aims to investigate the petrogenesis of the Late Cretaceous volcanic rocks using both new and previously existing geochemical and geochronological data. Based on the geochemical features, the studied volcanics are divided into Group I (dacite/rhyolite) and Group II (basalt/basaltic andesite). According to LA-ICP-MS zircon U-Pb data, the crystallization age of Group I is 83.43 +/- 0.87 Ma. The epsilon Nd(t) values of Group I are -1.4 and + 4.5, and the epsilon Nd(t) value of Group II is +3.0. The Lu-Hf isotope data from zircon shows that Group I have positive epsilon Hf(t) values (+14.20 - +12.15), and their crustal model age is 240-339 Ma. The epsilon Hf(t) values indicate that the Group I rocks are derived from the melting of a depleted mantle source. Whole-rock geochemistry data show that Group II samples were formed by partial melting of metasomatised spinel-bearing lherzolites at shallow depths. It is thought that the Late Cretaceous volcanic rocks are the products of arc magmatism associated with the northward subduction of the Neotethys oceanic lithosphere under the Eurasian plate, and the EPOB was an active continental margin arc during the Late Cretaceous.

&lt;p&gt;The Yuli belt in eastern Taiwan attests to tectonic evolution involving subduction metamorphism because two metam&amp;#233;lange units contain high-pressure (HP) blocks or layers of metaigneous rocks and serpentinites enclosed in metasedimentary schists. Metasomatic reaction zones occur locally along the contact between serpentinite (SP) and pelitic schist (PS). In the Tsunkuanshan area, we recognized five metasomatic zones. From PS to SP, the dominant minerals in each zone are: (I) albite, chlorite, phengite; (II) albite, amphibole, biotite, stilpnomelane; (III) chlorite, phengite, albite, epidote; (IV) epidote, chlorite, albite; and (V) talc, chlorite. Minor garnet and glaucophane are present in zone I and II, respectively. Field and petrographic observations combined with whole-rock major elements data suggest that this rock association was formed by diffusive exchanges between the PS and SP. Zones I - IV and PS samples show identical rare earth element (REE) patterns, indicating that these zones are of PS protolith. Hence, the original boundary between the PS and SP is likely in the zone IV and V. The isocon method was applied to quantify the mass balance among the metasomatic zones. The result shows mass changes in zones: I: +12%; II: -4%; III: +50%; IV: +56%. Enrichment of Ca is present in the entire reaction zones, especially the zone IV (up to 91%), whereas Na is only enriched within the zone I (~80%) and II (~89%). These enrichments are likely due to the involvement of external fluids. The formation of these metasomatic rocks was not only controlled by diffusive exchanges between PS and SP, but also by the Na and Ca rich fluid infiltrations. The existence of glaucophane within the zone II indicates that the metasomatism occurred under HP metamorphic conditions in a paleo-subduction interface.&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Keywords&lt;/strong&gt;: Fluid-rock interactions, isocon method, Na and Ca rich fluids, high-pressure, Yuli belt.&lt;/p&gt;

Intra-oceanic arc’s collision with an oceanic plateau plays a crucial role in the development of complex tectonic setting and induce subduction polarity reversal. Despite several studies and investigations, the origin and timing of subduction initiation in Solomon Island Arc (SIA) is still ambiguous. This study presents first robust zircon U-Pb ages and in-situ Hf isotope data from Choiseul, Santa Isabel (SI) and New Georgia Group (NGG), three major islands of SIA. Magmatic zircons and Hf isotope data from one gabbro sample, geochemically identical to N-MORB with Nb, Ta depletion in spidergram yielded 46 ± 1 Ma, which we decipher as the timing of Stage I magmatism by subduction of Pacific plate and subduction initiation in Choiseul. Six Choiseul andesites gave a mean age 206Pb/238U of 0.7 Ma, with εHf(t) values from +9 to +15 which represents the youngest crystallization age of Stage II magmatism with typical island arc-like signatures and a depleted mantle source. Detrital zircons from two sand sample yielded a population of mean age ranging from 0.3-0.7 Ma, 10 Ma and 48-46 Ma with εHf(t) values +9 to 15, +11 to +12 and +11 to +14 respectively and third sample has yielded a mean age 207Pb/206Pb 2.6 Ga and 500-1600 Ma with εHf(t) values -8 to +9, probably associated with Australian-type source indicating presence of a continental fragment beneath SIA. Similar ages of ca. 2.6 Ma have been obtained from inherited zircons from three gabbroic dyke sample from Santa Isabel with εHf(t) values +1 to +9 whereas one gabbroic dyke sample yields 110 ± 1 Ma, with εHf(t) values +14 to + 16 which we interpret as the basement age of SI. U-Pb dating of zircons from mafic to felsic rocks along NGG, covered mostly by Quaternary eruptive lavas. The youngest age population indicate Late Pliocene-Pleistocene 206Pb/238U ages, 2.5-1.5 Ma, interpreted as zircon crystallization ages of Stage II arc magmatism resulting from subduction of the Solomon Sea plate, as those of Choiseul Andesite. The first U-Pb age from ca. 36.8±0.5 Ma granite on Ghizo Island in New Georgia Group, revealing Late Eocene-aged magmatic zircon. This age represents the magmatic emplacement as the basement of plutonic rock from NGG that has not been reported before. We conclude that, (i) The Solomon Islands has a Cretaceous basement preserved in SI. (ii) The timing of subduction initiation and Stage I N-MORB type tholeiitic magmatism in SIA is 46 Ma followed by episodic eruptions from the early Eocene to late Eocene. (iii) Oligocene (30-20 Ma) magmatic hiatus, probably the time of subduction polarity reversal from subduction of Pacific plate to subduction of Solomon Sea plate. (iv) Stage II island arc magmatism initiated at 20-18 Ma in NGG to youngest emplacement age of Pliocene to Pleistocene in Choiseul as well as in NGG. (v)Abundant Archean zircons are present in samples from all three islands, indicate presence of micro-continent beneath Islands of Solomon. We are still working on the whole rock isotopic analysis to better constrain the tectonic and magmatic evolution of SIA.

The Jehol Biota comprises significant fossils that help to elucidate the evolution of Early Cretaceous terrestrial ecosystems. In this paper, we provide three new zircon U-Pb age constraints (124.3 & PLUSMN; 1.5 Ma, 124.9 & PLUSMN; 1.6 Ma, and 121.5 & PLUSMN; 1.4 Ma) from the base to the top of the Jiufengshan Formation (Xinganling Group) at the Naketa section in the north Great Xing'an Range of eastern Inner Mongolia, China, within a succession that contains the typical Eosestheria-Ephemeropsis trisetalis-Lycoptera davidi (EEL) assemblage of the Jehol Biota. Combined biostratigraphic and radio-isotopic dating suggests that the Jiufengshan Formation in the Naketa section corresponds to the upper part of the Yixian Formation and the lower part of the Jiufotang Formation, making it Barremian to earliest Aptian in age. Our findings allow us to test a widely accepted hypothesis about the migration and radiation of the Jehol Biota, and show that these organisms preserved within the lower part of the Jiufengshan Formation reached the Naketa area during the second and third evolutionary stages. The preservation of Jehol elements in the Naketa section provides valuable clues regarding the evolutionary history of the Jehol Biota and its spatiotemporal development. Furthermore, our study allows us to explore possible links between evolutionary processes and concurrent tectonism in the North China Craton, as the timing of this Jehol migration occurred when the tectonic setting changed from a compressional to an extensional regime.

In the last century, a blue–green colored gemstone known as Larimar with a special sea-wave pattern was discovered in the Dominican Republic. Larimar is composed of the mineral pectolite, which has a chemical composition of NaCa2Si3O8(OH) and is usually white in color. Cu2+ has always been considered to be the primary genesis of the blue color shown in Larimar, because native copper often grows together with Larimar. To clarify whether copper is the main reason for the origin of blue–green pectolite, we utilized laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) techniques to analyze trace elements in the pectolite samples and compared the relationship between elements and colors. The results show that vanadium and iron are the main origins of the sky-blue and green color of Larimar. We also discovered that it is not only the chemical elements that affect the color shades of the mineral, but the orientation of the radial fiber crystals also plays a critical role. The sea-wave pattern and the changes in the color saturation of radial pectolite are due to the transmittance of visible light through different viewed angles under changing crystal orientations. Our results reveal the chemical and physical factors behind the color and sea-wave pattern of Larimar. In addition, to our knowledge, this is the first time that the formation age of Larimar has been proven to be approximately equal to or younger than 40 ka, using the U-Th dating of calcite growth together with pectolite.

Precambrian metamagmatic complexes of the Zhingeldy and Kendyktas blocks of the Zheltau and ChuKendyktas terranes of the SW part of the Central Asian Orogenic Belt (CAOB) consist of predominant Neoproterozoic orthogneisses with the estimated protolith ages of ca. 790-800 Ma, and subordinate epidote and garnet amphibolites, metabasalts and metadolerites of the lower metamorphic grades. The orthogneisses are characterized by negative epsilon Nd(t) values of-12 to-4 with Nd model ages of 2.3-1.7 Ga, indicating their protoliths could have formed by a reworking of the Palaeoproterozoic crustal materials. Precambrian metavolcanic rocks in the studied region are rhyolites with the estimated crystallization ages of ca. 800-830 Ma, and are associated with metabasalts. Metasedimentary complexes in the studied region consist of intensively retrogressed garnet-mica schists interlayered with marmorized limestones, metasilicic rocks, epidote and garnet amphibolites and strongly altered eclogites. The inferred protoliths of the garnet-mica schists are terrigenous rocks accumulated during the latest Ediacaran - middle Cambrian and formed from Mesoproterozoic (ca. 1.0 Ga) and to a lesser extent Palaeoproterozoic felsic source rocks (ca. 1.6-1.7 Ga and ca. 2.5 Ga). The garnet-mica schists of the Kendyktas block have negative epsilon Nd(t) of-13.4 and a model age tNd(DM) of 2.2 Ga, implying formation of their protolith from Palaeoproterozoic crustal source. The studied Zheltau and Chu-Kendyktas terranes from the SW part of the CAOB have much in common in terms of Precambrian and Early Palaeozoic evolution and chemical compositions of the key rock types. The presence of the Early Precambrian rocks (Zheltau terrane), an abundance of the Late Mesoproterozoic (1000-1100 Ma) detrital zircons in the Ediacaran-Cambrian metasedimentary complexes and a wide distribution of the Late Neoproterozoic magmatism, are distinctive features of the studied terranes. We refer such Precambrian terranes of the western CAOB to the Ulutau-Moyunkum group where tectono-magmatic evolution is consistent with that observed from the northern part of the Tarim craton. Our results also aid comprehensive correlation of metamorphic complexes of the Precambrian terranes from the SW CAOB. (C) 2021 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Abstract We report new U–Pb zircon ages for mafic plutonic (gabbro) and volcanic (andesite) rocks, along with the whole-rock chemistry of a mafic–felsic suite of volcanic rocks from the Siang window of the Eastern Himalayan Syntaxis, NE India. Field relationships, and mineralogical and geochemical characteristics, of the studied mafic–intermediate–felsic rocks suggest their co-magmatic linkage that was generated in an extensional tectonic environment. Incompatible trace elements and low concentrations of large ion lithophile elements (LILEs) and REE behaviour reflect both the enriched nature of the mafic rocks and the limited influence of crustal contamination in their genesis. Partial melting and fractional crystallization processes have played a major role during the genesis of these felsic volcanics from the parental mafic magma. The laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb ages suggest that the mafic plutonic rock was emplaced at c. 121.18 ± 1 Ma and intermediate volcanic rock was emplaced at c. 135.48 ± 0.50 Ma during the Early Cretaceous period. The new ages are consistent with earlier reported zircon U–Pb ages (133.0 ± 1.9–130.7 ± 1.8 Ma) of felsic volcanic rocks from the present study area. Our new field observations, and mineralogical and geochemical characteristics, in conjunction with the U–Pb isotopic database suggest that the major magmatic event in the core of the Siang window of the Eastern Himalaya is coeval with the Rajmahal–Sylhet–Mikir–Shillong flood basalts of eastern and northeastern India, and the Comei–Bunbury Large Igneous Province of southeastern Tibet and SW Australia. These events are related to the break-up of eastern Gondwana and outbreak of the Kerguelen plume.

Net additions to the continental landmasses, or continental growth, is a process that has irrevocably shaped our environment throughout the Earth history. Studies of ancient orogens suggest that continental growth can be facilitated by plate tectonics-driven arc magmatism and material accretion along convergent margins. However, such details are not well-understood due to the geological complexity of ancient orogens. Specifically, the role of the magmatic arc and its contributions to growing an accretionary margin remains unclear. This study explores an under-studied, long-lived magmatic arc along a 1500 km-wide swath of the NE Asian continental margin between 42° to 52°N (i.e., Sikhote-Alin and adjacent NE China, Sakhalin, and Hokkaido). We present new igneous rock zircon U-Pb ages (n = 93) and geochemistry (n = 61) from Sikhote-Alin that complement limited published data (n > 60). We synthesize these data to reveal four episodes of arc magmatism at Sikhote-Alin, including (1) 134 to 120 Ma S-type, (2) 110 to 100 Ma I-type, (3) 95 to 52 Ma highly-evolved I-type, and (4) <46 Ma I-type. We then combine our new results with published data (n > 600) and geology from adjacent NE Asia to analyze overall magmatic trends during a ∼ 1500 km trenchward migration of arc magmatism driven by Jurassic to Cenozoic juvenile terrane accretion. The young, growing continental margin was modified by arc magmatism with chemical compositions determined by: (1) generation from a mantle wedge mixed with 1.3– 1.4% sediment component from the downgoing slab; and, (2) silica-enrichment from crustal magmatic differentiation. Here, convergent margin continental growth that involved crustal accretion and trenchward migrating arc magmatism show magma compositions that evolve from initial mantle source mixing followed by crustal differentiation.

Glaucophane-bearing metaplagiogranite occurs among the high-pressure (HP) metamorphic rock types poorly exposed in the Yuli belt. This lithologic association has been interpreted as scattered fragments of a meta-morphosed ophiolite. Through field and petrographic investigations, we have identified several types of meta-plagiogranite in the Chinshuichi area. This study reports the first U-Pb zircon dates by secondary ion mass spectrometry (SIMS) and whole-rock geochemical characterization of these metaplagiogranitic samples and associated metagabbro. The newly-obtained U-Pb zircon dates of 17.4-16.9 Ma are interpreted as magmatic crystallization ages. The delta O-18 averages of the dated zircon grains are 3.9-5.0 parts per thousand for the metaplagiogranites and 4.9 parts per thousand for the metagabbro, implying that the ultimate source rocks were of mantle origin. These metaigneous rocks are characterized by negative niobium tantalum anomalies in whole-rock composition. Protoliths of these HP metaigneous rocks may have formed in a nascent forearc setting related to an early Miocene subduction initiation. This finding infers that HP metamorphism of the Chinshuichi plagiogranite was caused by subduction erosion, and challenges some previous models that commonly postulated the South China Sea origin for the metaophiolitic fragments of the Yuli belt.

High-flux magmatic events, or flare-ups, are seen in many continental and transitional arcs but the underlying cause is not fully understood. Throughout Iran, voluminous calc-alkaline rocks emplaced between similar to 53 Ma and similar to 37 Ma are manifestations of a high-flux event. This high-flux event has been attributed to extension in the upper plate of one or more Neo-Tethyan subduction zones. Here, we present new findings in the UrumiehDokhtar paleo-arc, Iran where emplacement of Early Eocene granitic intrusions (ca. 55-52 Ma) immediately preceded the high-flux event. Geochemically, the studied rocks display high-K calc-alkaline compositions, continental crust-like trace element patterns, variable depletion of Y and heavy rare-earth elements, and Sr-Nd isotopes that are close to or slightly more enriched than the Bulk Silicate Earth. The Sr-Nd isotopic compositions indicate that the intrusions derived from upper plate materials. Relatively high Sr/Y and La/Yb of the studied rocks indicate that the residue of melt extraction, the crystalline assemblage that was left behind during magma differentiation, or both, to have existed in the deep arc crust. Following a similar to 20 Myr magmatic lull, the Early Eocene crustal thickening was most likely related to underthrusting of rear-arc crust towards the main arc, a process that not only promoted rapid root growth but also triggered the Eocene high-flux event. In the Iranian case example in particular, magmas formed during the high-flux event do not display elevated Sr/Y, implying that dense, locally thickened root might have foundered from the base of the arc lithosphere to the convecting mantle soon after their formation.

LA-ICP-MS U–Pb and Hf isotope analysis was conducted on zircons from the metamorphic unit of Omo Formation and a granodorite body of Tokunoshima in the Amami Islands, Southwest Japan. Zircons from dioritic gneiss (S9, S46) and pelitic schist (S99) yielded Paleoproterozoic upper intercept and Early Jurassic lower intercept ages. The positive εHf(t) values of the Paleoproterozoic zircons (between +12.7 and 0.8) and the negative εHf(t) values of the Jurassic zircons (−19.6 and −22.8) indicate Early Jurassic reworking of the older continental crust. The results suggest that the Omo Formation is an eastern equivalent of Cathaysia of the South China block. Zircons from granodiorite (S62) yielded a 206Pb/238U mean age of 61.3 ± 1.0 Ma with positive εHf(t) values of +12.0 and +12.6. The εHf(t) values indicate juvenile magmatic activity, which is correlated with that in the San-in batholith belt of Southwest Japan. Dioritic gneiss (S30) and psammitic schist (P91) yielded zircon U–Pb ages comparable to that of granodiorite (S62) with positive εHf(t) values (from +6.4 to +10.4). This suggests that the intrusion of the granodiorite induced the crystallization of zircon grains in the host rocks.

The Qiangtang terrane, which is divided into the North and South Qiangtang subterranes, is a key unit to study the evolution of the Paleo-Tethys Ocean in the Tibetan Plateau. Here we present new detrital zircon U-Pb and Lu-Hf isotopic data from a Paleozoic-Triassic sedimentary succession in the Qiangtang terrane. This new dataset is used to unravel the tectonic affinity of the North and South Qiangtang subterranes and the evolution of the Paleo-Tethys Ocean. Detrital zircons from the Paleozoic-Triassic sedimentary succession in the North Qiangtang sub-terrane are generally poorly rounded, indicating short transported distance. They yielded variable U-Pb ages ranging from 3399 Ma to 233 Ma with major age peaks of 358 Ma and 266-248 Ma, and epsilon Hf (t) values of-18.6 to 19.3. These features reveal that these detrital zircons were most likely derived from arc magmatic rocks, which were associated with the subduction of the Paleo-Tethys oceanic lithosphere. By contrast, detrital zircons from the Paleozoic sedimentary succession in the South Qiangtang subterrane are characterized by sphericity and ellipsoid, with most Th/U values > 0.1. They yielded U-Pb ages of 3624-321 Ma and three consistent age peaks of 549-527 Ma, 973-940 Ma and 2504-2470 Ma. They display epsilon Hf (t) values ranging from -33.4 to 26.2, with a cluster of -20.0 to 10.0. These features are similar to those of the detrital zircon grains from the South Qiangtang, Lhasa, and Himalaya terranes, as well as the Indian Gondwana. Detrital zircon ages data suggest that the North and South Qiangtang subterranes were derived from the Yangtze block and Gondwana, respectively. Available data indicate that the northward subduction of the Paleo-Tethys oceanic lithosphere was continuous at least during the Late Devonian to Triassic. The collision between the North and South Qiangtang subterranes was initiated at ~225 Ma.

Peridotites at water depths of 3430 to 5999 m have been discovered using the submersible Shinkai6500 (dives 6K-1397 and 6K-1398) on the southwestern slope of the 139°E Ridge (11°12′N, 139°15′E), a small ridge at the southwesternmost tip of the Mariana forearc near the junction with the Yap Trench and Parece Vela Basin. The peridotites studied consist of 17 residual harzburgites and one dunite and show various textures with respect to their depths. Peridotites with coarse-grained (> 1 mm) textures were sampled from the shallowest part (3705–4042 m) of the dive area, and peridotites with fine-grained (< 0.5 mm) textures were sampled deeper (5996 m). Olivine crystal-fabrics vary with grain size, with (010)[100] A-type patterns for the coarse-grained peridotites, {0kl}[100] D-type patterns for the fine-grained peridotites, and various indistinct patterns in samples of variable grain sizes. Fine-grained peridotites with D-type olivine crystal-fabrics could result from deformation under relatively higher flow stresses, suggesting that a ductile shear zone in the lithospheric mantle could occur in the deepest part of 139°E Ridge. Spinel Cr# range from relatively low (0.36) to moderately high (up to 0.57), and correlate with Ti contents (0.07–0.45 wt.%). The trace element patterns of clinopyroxene similarly exhibit steepening slopes from the middle to the light REEs regardless of textural variations. These mineralogical and geochemical features would result from melt-rock interactions under conditions of relatively shallow lithospheric mantle, which are much more comparable with the Parece Vela Basin peridotites than the Mariana forearc peridotites. Consequently, the Parece Vela Basin mantle is more likely exposed on the inner slope of the westernmost Mariana Trench, presumably due to the collision of the Caroline Ridge.

Metasomatic rocks in orogenic mélanges bear critical information about fluid-rock interactions and element mobilities during subduction processes. The Yuli belt contains a few mélange units that crop out high-pressure blocks of metaigneous rocks and serpentinites enclosed in metasedimentary rocks. Metasomatic rocks are found along contacts between the serpentinites and metasedimentary rocks. However, the protolith and formation of those metasomatic rocks are largely unknown. Meter-scale metasomatic zones occur at the contact between pelitic schists (PS) and serpentinites (SP) in the Tsunkuanshan area. Five zones from PS to SP are newly identified: (I) chlorite-albite schist, (II) amphibole-albite rock, (III) albite-chlorite schist, (IV) epidote-chlorite schist, and (V) chlorite-talc schist. Minor garnet and amphibole (glaucophane core - barroisite mantle - actinolite rim) are present in the zone I and II, respectively. Field and petrographic observations combined with whole-rock major elements data suggest that this rock association likely was formed by chemical exchanges between the SP and PS. However, the zone II shows enrichment of Si, Na, and Ca, but Al depletion relative to the other metasomatic rocks. This anomaly might be due to infiltration of external fluids. Rare earth element patterns of the PS, zone I, II, III, and IV are similar, indicating a similar protolith origin. Hence, the original boundary between the PS and SP is likely between the zone IV and V. We estimate the chemical mass balance from the PS to the metasomatic rocks (zone I, II, III, and IV) using the sparse isocon method (Kuwatani et al., 2020). The result shows that the chemical components in zone I, III, and IV are gained relative to the PS, whereas those in zone II are of loss. We interpret that the zone I, III, IV, and V were produced by diffusive exchanges of components between the PS and SP, whereas formation of the zone II was likely created by Na-Ca rich fluid infiltrations. The newly-found occurrence of glaucophane within the zone II indicates fluid-rock interactions during subduction metamorphism. Keywords: Chemical mass balance, sparse isocon method, Na-Ca rich fluids, Yuli belt.

Pontid Orojenik Kuşağı, Bulgaristan’dan başlayıp, Türkiye-Istranca Bölgesi'nden Küçük Kafkasya'ya kadar uzanan Doğu-Batı uzanımlı dağ kuşağını temsil etmektedir. İnceleme alanı Pontidler’in doğu kesiminde (Kaçkar Batoliti) Çamlıkaya köyü (İspir/Erzurum) ve çevresini kapsamaktadır. İnceleme alanında yüzeyleyen plütonik kayaçlar genel olarak granit ve granodiyoritler ile temsil edilmektedir. İncelenen kayaçlar, bileşimsel olarak kalkalkalen’den şoşonitiğe değişen karakterde ve I-tipi granit özelliğindedir. İlksel mantoya göre normalize edilmiş iz element diyagramlarında, Rb, K, Th, Ba gibi büyük iyon yarıçaplı elementlerde zenginleşme olduğu, Nb, Ti, P ve Ta gibi yüksek alan enerjili elementlerde ise fakirleşme olduğu görülmektedir. Granitik kayaçlarda gözlenen negatif Nb anomalisi yitimle ilişkili magmaların karakteristik özelliğidir. Kondrite göre normalize edilmiş iz element diyagramlarında, hafif nadir toprak elementleri, ağır nadir toprak elementlerine göre daha fazla zenginleşme göstermektedir. Negatif Eu anomalileri görülmektedir. Yüksek Rb/Sr, Nb/Ta, Zr/Hf, Th/U, Th/Ta ve düşük Nb/La gibi iz element oranları bu kayaçların oluşumunda kabuksal kirlenmenin etkin rol oynadığını göstermektedir. İnceleme konusunu oluşturan kayaçlar tektonik ayırtlama diyagramlarında volkanik yay ve çarpışma sonrası bölge alanlarına düşmektedir.

The white ignimbrite layer on top of volcanic sequences in the Coastal Range is the youngest eruption of the northern Luzon Arc in the Taiwan region.A gabbroic enclave was coexisting with the andesitic ignimbrite in this sequence.This study reports the dating results, textural and petrographic descriptions, and geochemical characteristics of the gabbroic enclave and andesitic breccias in the ignimbrite.Both components erupted approximately at 4 Ma, and show enrichment in large ion lithophile elements and depletion in high field strength elements, which are important island arc characteristics.Major and trace elements indicated that the andesitic magma shows larger fractionation and lower degrees of partial melting than the basaltic magma which formed the gabbroic enclaves.We suggest that three sub-stages of magmatism occur during the youngest eruption of the northern Luzon Arc at ~4 Ma.In the first sub-stage, the basaltic magma generated by higher degrees of partial melting from the source rose to a shallow reservoir and cooled to build up the gabbroic wall rocks.Later, lower degrees of partial melting magma were injected into the shallow reservoir and fractionated to intermediate magma causing the second substage.The third sub-stage was activated by the recharged magma, which triggered the intermediate magma to rise along the earlier pathway and assimilated within the gabbroic wall rock.This magma eventually erupted to form the andesitic ignimbrite with gabbroic enclaves within.

Although Peninsular Malaysia abundant Permo-Triassic Malayan granitic plutons and volcanics (292-198 Ma) generate an enormous volume of detrital zircons that masks other detrital sources in fluvial sediments, there are suggestions that Peninsular Malaysia could recycle detrital zircons from Indochina (through Jurassic-Cretaceous strata) to other parts of Sundaland by paleoriver after the Indochina-Sundaland sediment link diminishes in the Cenozoic. As there is insufficient data to prove this, we compiled our new detrital zircon U-Pb isotopic data from modern river sands in Peninsular Malaysia with all available data to create a dataset that revealed five detrital zircon age pattern zones: (1) Northeast Coastal Zone (-73 Ma and -223 Ma), (2) Mid-East Coastal Zone (-236 Ma and -280 Ma), (3) Southeast Coastal Zone (-170 Ma, -243 Ma, -291 Ma, 400-416 Ma and 1545-1852 Ma), (4) Central Zone (-220 Ma) and (5) Mid-West Coastal Zone (-227 Ma and 1105-1173 Ma). All detrital age pattern zones show a clear detrital contribution from Malayan granitoids and volcanics. However, the Southeast Coastal Zone also shows significant contributions from Jurassic-Cretaceous strata in the northwest, e.g. Bertangga and Gerek sandstones, making them comparable with sources from Indochina and Lower Cretaceous strata in Singapore. We suggest a defunct drainage during Paleogene which transports the eroded sediments from the Jurassic-Cretaceous strata in the northwest to the sink in the southeast coast of Peninsular Malaysia recycled "Indochina signature" detrital zircons. If the sink connects with the Sundaland paleoriver system, it might contribute to the "Indochina signature" detrital provenance in West Borneo.