RESUMO
The Twangiza-Namoya Gold Deposit within the Kibaran Belt of the Democratic Republic of the Congo represents a crucial manifestation of the hydrothermal gold system. This review investigates its intricate origin and the subsequent metallogenic evolution that has shaped its present-day characteristics and offers a systematic categorization based on its deposition processes and geotectonic settings. The findings reveal that the gold deposits are predominantly derived from sedimentary fluid sources. Within this vast metallogenic province, two stages of gold deposition have been constrained: (a) the early-stage formation related to the accretion of Rodinia assembly with subduction-collisional event where diagenesis cemented the syngenetic pyrite carbonaceous sediments and (b) the later stage deposition related to the continent-collisional event during the last stage of Rodinia supercontinent amalgamation. Previous isotopic investigations, with a particular emphasis on pyrite sulfur isotopes on both host rocks and vein-bearing sulfides, have been instrumental in tracing the origins of gold-bearing fluids in the study region. The isotopic variance in the four deposits: Twangiza (-5.2 % to +3 %, avg. -0.3 %), Kamituga (-0.6 % to -0.9.1 %, avg. -5%), Lugushwa (+3.0 % to -18.4 %), and Namoya, on the southernmost end, has a vast range but with much heavier isotope compositions, ranging between +1.3 % and to +22.6 %, with an average of +12.2 %. The data predominantly points to the sedimentary origins of ore fluids in the Twangiza-Namoya Gold belt, highlighting the pivotal role of sedimentary processes in shaping the metallogenic landscape of the region. The fluids inclusions depicted the deposits to be formed from H2O-Nacl-H2O with abundant CH4 and N2 ore-forming fluid, moderate temperature (350-500 °C), and low salinity. The overall results confirm the genetic style of the Twangiza-Namoya Gold Belt to be an orogenic gold-style deposit that was emplaced during the early Neoproterozoic era in low greenschist facies terrain.
RESUMO
Radiogenic isotopes of igneous and detrital minerals from various clastic rocks of mountain belts are used to reveal tectonic and sedimentary processes, which are otherwise difficult to detect. Here, we discuss the results of U-Pb and Lu-Hf zircon systems, and 40Ar/39Ar on detrital white mica in Eastern Alps. Zircon and white mica are chemically and mechanically stable and occur in magmatic, metamorphic and sedimentary rocks. During subsequent metamorphism, zircon is resistant against high temperature, >650â °C (U-Pb) and 900â °C (Lu-Hf). The Lu-Hf zircon system is used as a tracer of initial magma separation from the mantle, and the U-Pb zircon system records magmatic crystallization. The 40Ar/39Ar white mica system is stable up to 400-450â °C dating either formation or cooling after high-grade metamorphism. Detrital U-Pb zircon ages on two major rivers draining the Eastern Alps do not record any sign of Alpine orogeny or metamorphism. Consequently, U-Pb zircon studies can entirely miss the record of collisional orogeny in cool, magma-poor collision orogens. In contrast, 40Ar/39Ar white mica ages record Early and Late Alpine metamorphism but are limited to revealing the pre-orogenic history. U-Pb zircon and 40Ar/39Ar white mica yield different information in provenance studies. In the Eastern Alps, U-Pb zircon dating of magmatic and clastic rocks indicates intense formation of magmatic rocks between 630 and 230â Ma. Felsic rocks dominate the older age groups, and increasingly young mafic rocks were dated, specifically between 265 and 230â Ma. Hf isotopes record increasing juvenile input since â¼630 Ma. Two different groups with respect to Mesoproterozoic depleted mantle ages are shown: (1) one group with a Mesoproterozoic age gap typical for Gondwana-derived units, and (2) a rare group with Mesoproterozoic ages recording a new tectonic element in the Austroalpine basement in Alps.
RESUMO
Decades of empirical research have revealed how the geological history of our planet shaped plant evolution by establishing well-known patterns (e.g., how mountain uplift resulted in high rates of diversification and replicate radiations in montane plant taxa). This follows a traditional approach where botanical data are interpreted in light of geological events. In this synthesis, I instead describe how by integrating natural history, phylogenetics, and population genetics, botanical research can be applied alongside geology and paleontology to inform our understanding of past geological and climatic processes. This conceptual shift aligns with the goals of the emerging field of geogenomics. In the neotropics, plant geogenomics is a powerful tool for the reciprocal exploration of two long standing questions in biology and geology: how the dynamic landscape of the region came to be and how it shaped the evolution of the richest flora. Current challenges that are specific to analytical approaches for plant geogenomics are discussed. I describe the scale at which various geological questions can be addressed from biological data and what makes some groups of plants excellent model systems for geogenomics research. Although plant geogenomics is discussed with reference to the neotropics, the recommendations given here for approaches to plant geogenomics can and should be expanded to exploring long-standing questions on how the earth evolved with the use of plant DNA.
Assuntos
Plantas , Plantas/genética , Genômica , Evolução Biológica , Filogenia , Botânica , Genoma de Planta , GeologiaRESUMO
U-Pb dating was conducted for zircons from a total of 14 samples from 13 granite bodies in southwestern Cambodia using LA-ICP-MS. The granitic rock samples were collected from southwestern Cambodia, southwest of the Mae Ping Fault extending from northwest Cambodia via Tonle Sap Lake to southern Vietnam. The studied rock bodies belong to the ilmenite-series, except for three granitic rock bodies. They were identified as I-or A-type. The analysis yielded three distinct age ranges: 295-309, 191-232, and 75-98 Ma. The 295-309 Ma ages are associated with the Paleo-Tethys Sea subduction beneath the Indochina Block. The ages of 191-232 Ma may correspond to the amalgamation period of the Sibumasu and Indochina Blocks during the Indosinian Orogeny. Granitic rocks with ages of 75-98 Ma occur near the southeastern Cambodia-southern Vietnam border. Formation of these granitic rocks was associated with the Paleo-Pacific Ocean Plate (the Izanagi Plate) subduction beneath the Indochina Block. The region in which these granitic rocks occur is part of the Dalat-Kratie Zone.
RESUMO
Mountains play a key role in forming biodiversity by acting both as barriers to gene flow among populations and as corridors for the migration of populations adapted to the conditions prevailing at high elevations. The Anatolian and the Zagros Mountains are located in the Alpine-Himalayan belt. The formation of these mountains has influenced the distribution and isolation of the animal population since the late Cenozoic. Apathya is a genus of lacertid lizards distributed along these mountains with two species, i.e., Apathya cappadocica and Apathya yassujica. The taxonomy status of lineages within the genus is complicated. In this study, we tried to collect extensive samples from throughout the distribution range, especially within the Zagros Mountains. Also, we used five genetic markers, two mitochondrial (COI and Cyt b) and three nuclear (C-mos, NKTR, and MCIR), to resolve the phylogenetic relationships within the genus and explain several possible scenarios that shaped multiple genetic structures. The combination of results in the current study indicated eight well-support monophyletic lineages that separated to two main groups; group 1 including A. c. cappadocica, A. c. muhtari and A. c. wolteri, group 2 contains four regional clades Turkey, Urmia, Baneh and Ilam, and finally a single clade belonging to the species A. yassujica. In contrast to previous studies, Apathya cappadocica urmiana was divided into four clades and three clades were recognized within Iranian boundaries. The clades have dispersed from Anatolia to adjacent regions in the south of Anatolia and the western Zagros Mountains. According to the evidence generated in this study this clade is paraphyletic. Based on our assumption, orogeny activities and also climate fluctuations in Middle Miocene and Pleistocene have influenced to formation of lineages. In this study we revisit the taxonomy of the genus and demonstrate that the species diversity was substantially underestimated. Our findings suggest that each of the eight clades corresponding to subspecies and distinct geographic regions deserve to be promoted to species level.
Assuntos
Lagartos , Animais , Filogenia , Lagartos/genética , Irã (Geográfico) , DNA Mitocondrial/genética , Evolução Biológica , Variação GenéticaRESUMO
Background: The Svalbard Archipelago is commonly believed to have been located at comparable latitude and, possibly, to have been attached to Laurentia in the early Paleozoic (500-420 Ma) based on trilobite assemblage similarities. Trilobite assemblage differences and lack of mixing between Laurentia-Svalbard and Baltica were further used to propose that these continents were separated by the Iapetus Ocean at that time. However, recent structural correlation of Timanian (650-550 Ma) thrust systems throughout the Barents Sea show that Svalbard was already attached to Baltica in the latest Neoproterozoic and remained so during the Phanerozoic. Methods: The present study presents a new interpretation of seismic reflection data from the DISKOS database, which were tied to nearby exploration wells. The study uses recently acquired knowledge of the seismic facies of intensely deformed pre-Caledonian rocks and principles of seismic stratigraphy to interpret the data. Results: The present study reconciles the proximity of Svalbard and Laurentia with the early accretion of Svalbard to Baltica in the latest Neoproterozoic. It also describes the influence of Timanian thrust systems on paleoenvironments and possible effects on trilobite assemblages, e.g., the lack of mixing between those of Laurentia-Svalbard and Baltica. Conclusions: The identification of elongate, emerged topographic highs in the Barents Sea and Svalbard in the late Neoproterozoic-early Paleozoic suggest that paleontological constraints should be considered with greater care when discussing continent separation since thrust systems may act as major faunal barriers within a single tectonic plate. Other factors to consider when discussing plate separation include paleoclimatic belts.
Previous paleontological studies have used the differences in faunas (in the present case, now extinct fossil occurrences of trilobites) between two or more continental blocks (presently the Svalbard Archipelago, North America, and Scandinavia) to infer separation of these blocks by large distances up to several thousands of kilometers ca. 550 to 420 million years ago due to global plate tectonics processes. The present study shows that this method is biased because previous studies undermined factors such as climatic belts and (topographic) faunal barriers such as large, mountain-building cracks in the Earth's crust. The study builds on previous work on seismic data in the Barents Sea and Svalbard, which identified continuous, thousands of kilometers long, tens of kilometers thick networks of cracks extending from northwestern Russia to Svalbard and potentially northern Greenland, which formed 650 to 550 million years ago, therefore demonstrating a connection between all these continental blocks at 550-420 Ma.
RESUMO
Asia's rich species diversity has been linked to its Cenozoic geodiversity, including active mountain building and dramatic climatic changes. However, prior studies on the diversification and assembly of Asian faunas have been derived mainly from analyses at taxonomic or geographic scales too limited to offer a comprehensive view of this complex region's biotic evolution. Here, using the class Mammalia, we built historical biogeographic models drawn on phylogenies of 1,543 species occurring across Asia to investigate how and when the mammal diversity in Asian regions and mountain hotspots was assembled. We explore the roles of in situ speciation, colonization, and vicariance and geoclimatic events to explain the buildup of Asia's regional mammal diversity through time. We found that southern Asia has served as the main cradle of Asia's mammal diversity. Present-day species richness in other regions is mainly derived from colonization, but by the Miocene, in situ speciation increased in importance. The high biodiversity present in the mountain hotspots (Himalayas and Hengduan) that flank the Qinghai-Tibetan plateau is a product of high colonization instead of in situ speciation, making them important centers of lineage accumulation. Overall, Neogene was marked by great diversification and migrations across Asia and surrounding continents but Paleogene environments already hosted rich mammal assemblages. Our study revealed that synchronous diversification bursts and biotic turnovers are temporally associated with tectonic events (mountain building, continental collisions) and drastic reorganization of climate (aridification of Asian interior, intensification of Asian monsoons, sea retreat) that took place throughout the Cenozoic in Asia.
Assuntos
Biodiversidade , Mamíferos , Animais , Humanos , Mamíferos/genética , Ásia , Povo Asiático , ClimaRESUMO
Vicariance is the simplest explanation for divergence between sister lineages separated by a potential barrier, and the northern Andes would seem to provide an ideal example of a vicariant driver of divergence. We evaluated the potential role of the uplift of the Eastern Cordillera (EC) of the Colombian Andes and the Mérida Andes (MA) of Venezuela as drivers of vicariance between lowland populations co-distributed on both flanks. We synthesized published geological data and provided a new reconstruction showing that the EC-MA grew from north to south, reaching significant heights and separating drainages and changing sediment composition by 38-33 million years ago (Ma). A few lowland passes across the EC-MA may have reached their current heights (~1,900 m a.s.l.) at 3-5 Ma. We created a comparative phylogeographic data set for 37 lineages of lowland tetrapods. Based on molecular phylogenetic analyses, most divergences between sister populations or species across the EC-MA occurred during Pliocene and the Quaternary and a few during the latest Miocene, and coalescent simulations rejected synchronous divergence for most groups. Divergence times were on average slightly but significantly more recent in homeotherms relative to poikilotherms. Because divergence ages are mostly too recent relative to the geological history and too asynchronous relative to each other, divergence across the northern Andes may be better explained by organism-environment interactions concomitant with climate oscillations during the Pleistocene, and/or dispersal across portals through the Andes.
Assuntos
Clima , Filogeografia , Filogenia , Colômbia , VenezuelaRESUMO
The phylogeography of the Kaloula genus in East Asia is still poorly understood. One of the difficulties is the absence of fossils to corroborate molecular dating estimates. Here, we examined the mitochondrial structure of Kaloula spp. in East Asia and focused on the impact of glaciations on the northernmost species: Kaloula borealis. We determined the phylogenetic relationships, molecular dating, and genetic connectivity assessments within the genus from 1211 bp of concatenated mitochondrial 12S and 16S. The relaxed clock analyses reveal the emergence of Kaloula spp. common ancestor in East and Southeast Asia between the Eocene and Oligocene, c. 38.47 Ma (24.69-53.65). The genetic diversification of lineages then increased on the East Asian Mainland during the Lower Miocene, c. 20.10 (8.73-30.65), most likely originating from the vicariance and radiation triggered by the orogeny of the Qinghai-Tibetan Plateau. Later, the dispersal towards the North East Asian Mainland during the Upper Miocene drove the population diversification of K. borealis c. 9.01 Ma (3.66-15.29). Finally, the central mainland population became isolated following orogenesis events and diverged into K. rugifera during the Pliocene, c. 3.06 Ma (0.02-10.90). The combination of population genetic and barrier analyses revealed a significant genetic isolation between populations of Kaloula spp. matching with the massive Qinling-Daba Mountain chain located in south-central China. Finally, we highlight a young divergence within the Eastern Mainland population of K. borealis, possibly attributed to refugia in south eastern China from which populations later expanded.
Assuntos
Anuros , Refúgio de Vida Selvagem , Animais , Anuros/genética , Fósseis , Filogenia , FilogeografiaRESUMO
BACKGROUND: The orogeny of the eastern Mediterranean region has substantially affected ecological speciation patterns, particularly of mountain-dwelling species. Mountain vipers of the genus Montivipera are among the paramount examples of Mediterranean neo-endemism, with restricted ranges in the mountains of Anatolia, the Levant, Caucasus, Alborz, and Zagros. Here we explore the phylogenetic and ecological diversification of Montivipera to reconstruct its ecological niche evolution and biogeographic history. Using 177 sequences of three mitochondrial genes, a dated molecular phylogeny of mountain vipers was reconstructed. Based on 320 occurrence points within the entire range of the genus and six climatic variables, ecological niches were modelled and used to infer ancestral niche occupancy. In addition, the biogeographic history and ancestral states of the species were reconstructed across climate gradients. RESULTS: Dated phylogenetic reconstruction revealed that the ancestor of mountain vipers split into two major clades at around 12.18 Mya followed by multiple vicariance events due to rapid orogeny. Montivipera colonised coastal regions from a mountain-dwelling ancestor. We detected a highly complex ecological niche evolution of mountain vipers to temperature seasonality, a variable that also showed a strong phylogenetic signal and high contribution in niche occupation. CONCLUSION: Raising mountain belts in the Eastern Mediterranean region and subsequent remarkable changes in temperature seasonality have led to the formation of important centres of diversification and endemism in this biodiversity hotspot. High rates of niche conservatism, low genetic diversity, and segregation of ranges into the endemic distribution negatively influenced the adaptive capacity of mountain vipers. We suggest that these species should be considered as evolutionary significant units and priority species for conservation in Mediterranean mountain ecosystems.
Assuntos
Evolução Biológica , Ecossistema , Biodiversidade , Região do Mediterrâneo , FilogeniaRESUMO
Pseudopimelodus is a Neotropical genus of bumblebee catfish, composed of four valid species occurring in both trans- and cis-Andean rivers of South America. The orogeny of the Andes has led to diversification in the genus Pseudopimelodus in Colombia. This study analyzed partial sequences of mitochondrial cox1 and nuclear rag2 genes to test the hypothesis that the species, nominally recognized as P. schultzi and P. bufonius in Colombia, correspond to more than two different evolutionary lineages. Results indicate high levels of genetic divergence among individuals of nominal P. schultzi and P. bufonius, from trans- and cis-Andean basins in Colombia. In addition, five divergent lineages of Pseudopimelodus were confidently delimited by using a single-locus species-discovery approach and confirmed by species tree analyses. Additionally, molecular-clock dating showed that most diversification processes in Pseudopimelodus took place during the Miocene, when Andean tectonic evolution was occurring in northwestern South America. The present study provides, for the first time, phylogeographic insight into this Neotropical genus.
RESUMO
More than 100 million people around the world are endangered by geogenic arsenic (As) in groundwater, residing in sedimentary aquifers. However, not all sedimentary aquifers are groundwater As enriched, and the ultimate source of As in enriched aquifer sediments is yet-unknown, globally. A reconnaissance of the major aquifers suggests that major As enriched aquifers are predictably systematic on a global scale, existing in sedimentary foreland basins in the vicinity of modern or ancient orogenic systems. In conformity with the Principle of Uniformitarianism, we demonstrate that the groundwater As comes from magmatic arcs (primary source) in present (e.g. Andes) or ancient (e.g. Himalaya) continental convergent margins of some of the most prominent orogenic systems across the globe, and ends up in sediments (secondary source) in adjoining foreland or related basins that eventually act as aquifers. These arc magmas scavenge As while rising through the deep continental crust. Erosion of such orogens ultimately increases the bulk As content in sediments of adjoining basins, leading to groundwater As enrichment in downstream aquifers. Such As-polluted aquifers are eventually extensively used for groundwater exploitation, for drinking and other human purposes. Surface geological and biogeochemical processes, like redox reactions, are conducive to such groundwater As enrichment. We suggest this model by integrating our study of long-time observations in Himalayan and Andean basin aquifers, and generalizing 63 major aquifers across the globe, to demonstrate the source-to-sink transport of As, thereby delineating it's geogenic cycling in the subsurface. This work outlines the specifics of the mechanisms that would drive the processes of groundwater As enrichment across spatio-temporal scales, i.e. tectonic-scale taking place over millions of years on continental-scale and groundwater pollution taking place at human time-scales on village to household scale. Thus, in this work, we demonstrate a direct evidence of connectivity between global geological processes and individual human health.
RESUMO
Much of the immense present day biological diversity of Neotropical rainforests originated from the Miocene onwards, a period of geological and ecological upheaval in South America. We assess the impact of the Andean orogeny, drainage of Lake Pebas and closure of the Panama isthmus on two clades of tropical trees (Cremastosperma, ca 31 spp.; and Mosannona, ca 14 spp.; both Annonaceae). Phylogenetic inference revealed similar patterns of geographically restricted clades and molecular dating showed diversifications in the different areas occurred in parallel, with timing consistent with Andean vicariance and Central American geodispersal. Ecological niche modelling approaches show phylogenetically conserved niche differentiation, particularly within Cremastosperma. Niche similarity and recent common ancestry of Amazon and Guianan Mosannona species contrast with dissimilar niches and more distant ancestry of Amazon, Venezuelan and Guianan species of Cremastosperma, suggesting that this element of the similar patterns of disjunct distributions in the two genera is instead a biogeographic parallelism, with differing origins. The results provide further independent evidence for the importance of the Andean orogeny, the drainage of Lake Pebas, and the formation of links between South and Central America in the evolutionary history of Neotropical lowland rainforest trees.
RESUMO
The timing of continental collision between India and Asia has been controversial for a long time because of the difficulty in screening isotopic ages for different types of tectonothermal event along the convergent continental boundary. After distinguishing the collisional orogeny from the precollisional accretionary orogeny and the postcollisional rifting orogeny, an age range of 55⯱â¯10â¯Ma is obtained to mark the collisional orogeny in the Early Cenozoic rather than throughout the Cenozoic. This age range provides the resolution to the timing of tectonic reactivation not only for reworking of the marginal arc systems in the Early Cenozoic but also for overprinting of granulite facies metamorphism on eclogites in the Late Cenozoic. In particular, superimposition of the rifting orogeny on both accretionary and collisional orogens in the Late Cenozoic is the key to the reactivation of both Gangdese and Himalayan orogens for contemporaneous metamorphism and magmatism at high thermal gradients. Therefore, rise of the plateau may be caused by underplating of the asthenospheric mantle for rifting orogeny in the composite Himalayan-Tibetan orogens after foundering of their roots in the Late Cenozoic.
RESUMO
BACKGROUND AND AIMS: Recent biogeographic studies have illustrated that Quaternary climatic changes and historical orogenies have driven the development of high levels of biodiversity. In this context, phylogenetic niche conservatism may play a role as a major precursor of allopatric speciation. However, the effects of niche evolution on the diversification patterns of plant species under rapid habitat changes are still unknown. Here, Primula section Reinii, one of the few primroses endemic to the Japanese Archipelago, was investigated. This study aimed to clarify the phylogenetic position and relationships of section Reinii, interpret the biogeographic and diversification patterns of this group and gain a better understanding of the role of climatic niche evolution in the Japanese endemic primroses. METHODS: Dated phylogeny for Primula section Reinii is presented based on the sequences of six chloroplast genes and one nuclear gene. Biogeographic history was reconstructed using statistical dispersal-vicariance analysis. Macro-evolutionary modelling of the climatic niche was combined with biogeographic inferences. KEY RESULTS: Section Reinii was shown to be monophyletic based on chloroplast and nuclear sequences. Fossil-calibrated dating analysis estimated that this section diverged from its sister taxon, sect. Cortusoides, around 1.82 million years ago, and intraspecific diversification occurred within the last million years. This time frame was characterized by Quaternary climatic oscillations and uplift of high mountains in Japan. Biogeographic inference suggested that this section originated at the northern end of the Japanese Archipelago and then dispersed southward to other islands. Models of climatic niche evolution indicated that the closely related species P. reinii and P. tosanensis have contrasting niche optima and rates of niche evolution. CONCLUSION: Our results highlight that spatiotemporal heterogeneity in the Japanese islands may play a significant role in the biogeographic history of Japanese endemic primroses. Contrasting evolutionary processes found in closely related species illustrate the effects of climatic niche evolution on species' diversification patterns.
Assuntos
Evolução Biológica , Mudança Climática , Primula/genética , Fósseis , Especiação Genética , Japão , Filogenia , Proteínas de Plantas/genéticaRESUMO
The diverse biota of New Guinea includes many nominally widespread species that actually comprise multiple deeply divergent lineages with more localised histories of evolution. Here we investigate the systematics of the very large geckos of the Cyrtodactylus novaeguineae complex using molecular and morphological data. These data reveal two widespread and divergent lineages that can be distinguished from each other, and from type material of Cyrtodactylus novaeguineae, by aspects of size, build, coloration and male scalation. On the basis of these differences we describe two new species. Both have wide distributions that overlap extensively in the foothill forests of the North Papuan Mountains, however one is seemingly restricted to hill and lower montane forests on the ranges themselves, while the other is more widespread throughout the surrounding lowlands. The taxon endemic to the North Papuan Mountains is related to an apparently lowland form currently known only from Waigeo and Batanta Island far to the west - hinting at a history on island arcs that accreted to form the North Papuan Mountains.
RESUMO
The western sector of the Qinling-Dabie orogenic belt plays a key role in both Late Jurassic to Early Cretaceous "Yanshanian" intracontinental tectonics and Cenozoic lateral escape triggered by India-Asia collision. The Taibai granite in the northern Qinling Mountains is located at the westernmost tip of a Yanshanian granite belt. It consists of multiple intrusions, constrained by new Late Jurassic and Early Cretaceous U-Pb zircon ages (156 ± 3 Ma and 124 ± 1 Ma). Applying various geochronometers (40Ar/39Ar on hornblende, biotite and K-feldspar, apatite fission-track, apatite [U-Th-Sm]/He) along a vertical profile of the Taibai Mountain refines the cooling and exhumation history. The new age constraints record the prolonged pre-Cenozoic intracontinental deformation as well as the cooling history mostly related to India-Asia collision. We detected rapid cooling for the Taibai granite from ca. 800 to 100 °C during Early Cretaceous (ca. 123 to 100 Ma) followed by a period of slow cooling from ca. 100 Ma to ca. 25 Ma, and pulsed exhumation of the low-relief Cretaceous peneplain during Cenozoic times. We interpret the Early Cretaceous rapid cooling and exhumation as a result from activity along the southern sinistral lithospheric scale tear fault of the recently postulated intracontinental subduction of the Archean/Palaeoproterozoic North China Block beneath the Alashan Block. A Late Oligocene to Early Miocene cooling phase might be triggered either by the lateral motion during India-Asia collision and/or the Pacific subduction zone. Late Miocene intensified cooling is ascribed to uplift of the Tibetan Plateau.