East Malaya Research Articles

Revision of the Early Carboniferous trilobite Linguaphillipsia, with a new species from Terengganu in Peninsular Malaysia

This study examines the morphology and palaeobiogeography of species assigned to the Early Carboniferous trilobite Linguaphillipsia. We recognize 27 valid species found in Tournaisian and Viséan deposits worldwide. We provide an updated generic diagnosis, with four previously recognized species groups revised. The terapaiensis-group and scabra-group are considered synonymous, while the longicornuta-group and strabonis-group are retained. Linguaphillipsia exhibits a restricted palaeogeographical distribution around the tropical Palaeo-Tethys Ocean, together with the shallow marine margins of eastern Gondwana (Australia). During the Tournaisian, 15 species of Linguaphillipsia ranged across what is now Europe, Asia, and eastern Australia, each showing distinct provincialism. This distribution persisted into the Viséan, although the number of species decreased, particularly in eastern Palaeo-Tethys of Asia. The genus did not survive to the end of the Mississippian. In addition, we describe a new species, Linguaphillipsia buchuensis sp. nov., from Bukit Buchu in Terengganu, Peninsular Malaysia (East Malaya Block). Based on faunal similarities, we correlate the Bukit Buchu beds with the Charu Formation in Pahang and assign the unit a Viséan (middle Mississippian) age. Hung Yung Tang [tanghungyung@gmail.com], Department of Geology, University of Malaya, Kuala Lumpur 50603, Malaysia; Marine Geoscience Program, Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia; Masatoshi Sone [masatoshi.sone@gmail.com], Department of Geology, University of Malaya, Kuala Lumpur 50603, Malaysia; David K. Brezinski [david.brezinski@maryland.gov], Maryland Geological Survey, 2300 St. Paul Street, Baltimore, Maryland 21218, USA; Yu He Teng [yuheteng@gmail.com], Academy of Sciences Malaysia, 50480 Kuala Lumpur, Malaysia; Hasrizal Shaari [riz@umt.edu.my], Fatin Izzati Minhat [fatinminhat@umt.edu.my], Marine Geoscience Program, Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia; Institute of Oceanography and Environment (INOS), Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia.

Structural and Geochemistry of Air Piau Gold Mineralisation in Kelantan, North-East Peninsular Malaysia

The formation of the Air Piau Gold Deposit in North-East Peninsular Malaysia due to Permo–Triassic subduction and collision between Sibumasu and East Malaya blocks and resulted in several phases of deformation, contraction, and metamorphism. Kinematic and petrography study of quartz veins in Air Piau area observed whether following the foliation of metamorphic rock or crosscut the foliation. Early generation of veining system in Air Piau follow the host rock foliation (V1). Meanwhile the later formation of the hydrothermal vein has a cross-cutting relationship with foliation (V2). Some veins observed were sheared and brecciated (V3). Positive correlation between Au and As concentration that can be characterized these deposit formed at mesozonal zone. V3 vein type showed the brecciated texture of vein indicates the brittle structure deformation. The conceptual model of orogenic gold, this type of V3 vein can be classified as epizonal zone. Regionally, the Air Piau gold deposit shares geologically similarities (in term of tectonic setting, geological structures controlled, host rock, ore gechemistry) with many other sediment/metasediment- hosted, orogenic gold deposits in Peninsular Malaysia such as Tersang, Selinsing and Penjom. Furthermore, Air Piau gold deposit characteristics as discussed before supported the theory related with orogenic/mesothermal gold from various researchers However, a number of inferences on classified Air Piau gold deposit model as orogenic gold deposit remains speculative in the absence importance data like ore geochemistry data (Hg, Sb and Te element concentrations) and fluid inclusion data.

Two new Chelonocoris species from Borneo and Sumatra (Hemiptera, Heteroptera, Aradidae)

Chelonocoris bakonyii sp. n. from Borneo (East Malaya) and Ch. heissi sp. n. from Sumatra (Indonesia) is described on the basis of male specimens. The female holotype of C. usingeri Kormilev, 1956 from Borneo is depicted. With 19 figures.

Triassic felsic magmatism in SE Peninsular Malaysia: Petrogenesis and geodynamic implications for the Eastern Paleotethyan tectonic transition

Middle–Late Triassic volcanism and contemporary granitoids in East Malaya provide significant insights into the magmatic evolution and geodynamic processes of the Paleotethyan Ocean in SE Asia. This paper presents new zircon ages and whole-rock geochemical data including Sr-Nd-Pb-Hf isotopic analyses for newly identified felsic volcanic rocks and granites in SE Peninsular Malaysia. Zircon geochronological data constrain their formation time at 238–235 Ma. All samples have relatively high SiO2 contents with enrichment in light rare earth elements but have negative anomalies at Nb, Ta, Ti, and Eu on spidergrams. Calculated zircon saturation temperatures are between 840 °C and 957 °C. Samples have (87Sr/86Sr)i ratios between 0.70501 and 0.71014 and εNd (t) values ranging from −6.6 to −5.9, with (206Pb/204Pb)i = 18.45–18.77, (207Pb/204Pb)i = 15.68–15.71, and (208Pb/204Pb)i = 38.88–38.97. The zircon in-situ εHf (t) values and TDM2 ages range from −5.6 to +4.5 and 1.62 Ga to 0.98 Ga, respectively. The primary melting source which produced these felsic volcanic rocks and granites was Proterozoic crustal rocks with a juvenile middle-lower crustal component. Triassic volcanism in SE Peninsular Malaysia northerly correlates with synchronous volcanic rocks in the Lancangjiang and Chiang Khong-Lampang-Tak volcanic zones. Our data, along with regional observations, indicate that these volcanic rocks and granites formed in a localized extensional setting in response to the Paleotethyan slab breakoff. While the initial collision of Sibumasu with East Malaya may have occurred at ∼237 Ma.

Multiple stages of continental rifting in Eastern Peninsular Malaysia: new insights from Jurassic–Cretaceous granitoids

Mesozoic granitoids in Peninsular Malaysia provide crucial information on the temporal–spatial relationship between the Tethyan and Palaeo-Pacific domains. This paper presents new ages and geochemical data for newly identified Jurassic–Cretaceous granites and meta-granites from East Malaya. These granitoids can be divided into three groups. Group 1 consists of high-K calc-alkaline granites and granodiorites (171–162 Ma) with variable ε Nd ( t ) values of −7.4–+0.5, zircon ε Hf ( t ) values of −7.4–+8.6, and high initial ratios for 206 Pb/ 204 Pb (20.04–20.65), 207 Pb/ 204 Pb (15.73–15.79) and 208 Pb/ 204 Pb (39.80–40.20). The melting of metasedimentary rocks with a juvenile mafic component formed Group 1 samples. Group 2 granite porphyries ( c. 131 Ma) with A-type affinities and Group 3 granitic gneisses ( c. 130 Ma) with I-type affinities share similar ε Nd ( t ) values (−7.2 to −5.5), zircon ε Hf ( t ) values (−10.1–+6.5), and initial ratios for 206 Pb/ 204 Pb (18.81–19.02), 207 Pb/ 204 Pb (15.71–15.77) and 208 Pb/ 204 Pb (38.95–39.59). Although Group 2 and 3 samples were derived from an ‘ancient’ meta-mafic source region, Group 2 shows evidence for the involvement of a juvenile mafic component. All these granitoids are akin to the Permian–Triassic igneous rocks in East Malaya. The Jurassic–Cretaceous igneous rocks in Eastern Peninsular Malaysia were formed during multiple stages of continental rifting in response to Palaeo-Pacific slab rollback pulses rather than by Tethyan evolutionary processes. Supplementary material : Data for the Middle Jurassic–Early Cretaceous granitoids of East Malaya are available at https://doi.org/10.6084/m9.figshare.c.6689085 Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change

Late Paleozoic–Early Mesozoic granitic rocks in Eastern Peninsular Malaysia: New insights for the subduction and evolution of the Paleo-Tethys

• The granitoids in East Malaya were emplaced at 289–244 Ma. • The granitoids were formed in response to the Paleotethyan subduction . • The slab roll-back of the Eastern Paleotethyan initially occur at ∼ 270 Ma. • Subduction-related granitoids in East Malaya can extend to SW China and W Borneo. Well-preserved Late Paleozoic–Early Mesozoic igneous rocks in Peninsular Malaysia are important for investigating the Paleotethyan tectonic evolution. This study presents new zircon U-Pb dating, whole-rock geochemical, and Sr-Nd-Pb-Hf isotopic data for granitoids identified from the East Malaya. By utilizing all available data, the Permian–Middle Triassic granitoids in Eastern Peninsular Malaysia can be divided into three groups. Group A (289–270 Ma) I-type granites have higher ε Nd (t) values of − 6.6 to − 2.6 and zircon ε Hf (t) values of − 7.1 to + 4.9 than Group B S-type granites (285–272 Ma) with ε Nd (t) = − 10.1 and zircon ε Hf (t) = − 23.1 to + 1.5. Group C (254–244 Ma) with A-type characteristics, has ε Nd (t) and zircon ε Hf (t) values ranging from − 7.3 to − 3.8 and − 8.9 to + 2.2, respectively. The Pb isotopic values for three groups are similar with ( 206 Pb/ 204 Pb) i = 18.71–19.43, ( 207 Pb/ 204 Pb) i = 15.66–15.71 and ( 208 Pb/ 204 Pb) i = 38.27–39.43. Group A was derived from metaigneous rocks with a juvenile mafic component, while Group B was from metasedimentary rocks. Group C had a mixed source of “ancient” meta-mafic rocks with a juvenile mafic component. This study proposes that the Late Paleozoic–Early Mesozoic granitoids were formed in response to the subduction of the Paleotethyan Ocean, and that a tectonic transition from subduction to slab roll-back might occur at ∼ 270 Ma. Subduction-related granitoids in East Malaya can northernly extend to the Tachileik Batholith in eastern Myanmar and Jinghong in SW China, and southernly link with W Borneo.

Metamorphic Evolution of the Baling Formation at Banding Island, Perak, Malaysia

This paper presented new study on the mineral assemblages and the compositions on the rocks protolith. Banding island and its surrounding area are dominated by low-grade regional metamorphism which located within the East Malaya Block and dated from Ordovician to Permian age. The study area is situated at longitudes of 101° 22’ 25”E to 101° 22 35”E and latitudes at 5° 33’ 47”N to 5° 32’ 95”N. The metamorphic rocks consist of phyllite, mica schist, and metasandstone interbedded with slate. Majority of the phyllite are highly weathered with visible joint. Phyllite in the study area contains quartz veins with thickness varies from 0.5 cm to 6 cm, that follows the direction of rock foliation. Phyllite is dominated with mica group with major muscovite mineral, and the mica is mostly muscovite. While the mica shist is also dominated with mica group with muscovite mineral. The intensity of the regional metamorphism is lowest from the west of the Banding Island to slightly moderate metamorphism toward the east of the study area, which supported by the changes of the metamorphic rock type from phyllite to schist according to the petrographic analysis. Regionally, Perak state especially in Gerik area are dominated by rocks from Paleozoic era as Perak is located in Western Belt of Peninsular Malaysia.

New sedimentary constraints for the Late Devonian north-dipping Paleo-Tethys subduction and its eastern continuation on Hainan Island, South China

As a major boundary between the Simao-Indochina and South China blocks, the Jinshajiang–Ailaoshan–Song Ma suture zone preserves the remnants of a back-arc basin or a branch of the Paleo-Tethys Ocean. However, whether this suture zone extends eastward to the Hainan Island is still controversial. Here, we use detrital zircon U–Pb geochronology to explore the source-to-sink characteristics of the Lower Carboniferous-Lower Permian strata in Hainan Island and mainland southeast China (SE China). The results, combined with published data for the Devonian-Triassic sandstones from Hainan and SE China, show that the Devonian-Lower Permian samples display similar detrital zircon age populations at ∼430 Ma, ∼930–980 Ma, ∼1600–1800 Ma and ∼2400 Ma. However, the Upper Permian-Triassic sandstones have a predominant zircon population at ∼370 Ma, indicating a dramatic change in the detritus provenance for Hainan-SE China since the early Late Permian. The presence of similar 400-350 Ma detrital zircons peaked at ∼370 Ma with ϵHf(t) values from −12 to +3 in the sedimentary rocks from both Hainan-SE China and Simao-Indochina blocks indicates that these two terranes should have a similar detritus source with abundant Late Devonian magmatic rock exposure during the Late Permian-Triassic. These Late Devonian magmatic rocks were most likely formed by the north-dipping Paleotethyan subduction. This conclusion is consistent with the recent discovery of Upper Devonian arc-related tuffs, volcaniclastics, tuffaceous chert and rhyolite in the North Qiangtang, Simao-Indochina and East Malaya terranes, and possibly also in the southern Hainan. These Upper Devonian rocks could have acted as detritus source for the basins in SE China-Hainan, as well as the Youjiang Basin in SW China, after the collision between the Indochina and South China blocks. Combined with the transition from a carbonate platform to clastic facies in the early Late Permian in SE China, the Indochina-South China collision on Hainan Island may have occurred at ∼266-260 Ma, earlier than that (∼250-230 Ma) along the Jinshajiang–Ailaoshan–Song Ma suture zone. Such a temporal–spatial source-to-sink relationship between the Late Devonian arc and basins on the southern margin of South China suggests that SE China-Hainan should be located within the Paleo-Tethys rather than the Paleo-Pacific tectonic domain during the Early Carboniferous-early Late Permian.

Geochemical Distribution of REE and Grain Size Analysis of Heavy Mineral Associated with Tin Placer-Type Deposit, Bangka

Indonesia is included in the East Malaya Block of the Southeast Asian Tin Belt. Two types of tin deposits in Indonesia are primary and secondary tin deposits (placer). Factors that can cause the formation of placer tin deposits include S-type granite, weathering, transportation, and sedimentation. Factors that control the formation of placer tin deposits include the presence of source rock (granite type S), weathering processes, erosion, transportation and sedimentation, and the presence of basins or valleys where weathering materials are deposited. The transportation process has a major role in the grain shape of a material. This study aims to determine the geochemical distribution and characteristics of heavy mineral grains at the accumulation of placer tin deposits, e.g., colluvial, alluvial, and tailings, in which there are 62 sample points located Bangka Island, Indonesia. The research method used in this study was grain size analysis, radiation level measurement using a scintillometer, and geochemical analysis using ICP-MS.

Malayacyclus gen. nov., the first Southeast Asian Cyclida (Crustacea) from the Early Carboniferous of Terengganu, Malaysia

Malayacyclus terengganuensis, a new genus and species of the Cyclida (Crustacea), is reported from the Early Carboniferous (Visean) of Terengganu, eastern Peninsular Malaysia (East Malaya Block). The new genus possesses diagnostic features of both families Cyclidae and Americlidae. Plus, it develops the trifurcate posterior spines: a unique morphology that was not previously known for any cyclidan genera. Based on the possession of an anterior rostrum and optic notches, it is tentatively included in the Americlidae. This represents the first find of the Cyclida from Southeast Asia and the second from the Carboniferous of Asia (eastern Tethys).

Peninsular Malaysia transitional geodynamic process from Gondwana to Pangaea: New constraints from 500 to 200 Ma magmatic zircon U-Pb ages and Hf isotopic compositions

The geodynamic process from the evolution of supercontinent has distinct isotope characteristics explorable using zircon Hf isotopic composition. Since Peninsular Malaysia associates with Gondwana dispersal and Pangaea formation, analyzing the U-Pb and Hf-isotopic content of its 500–200 Ma magmatic zircon could reveal the signal left by the transitional geodynamic process between the supercontinents. We collected two groups of magmatic rocks from West Malaya: Ordovician meta-volcanics (n = 8), and Triassic Main Range granitoid province (MRGP) (n = 6); and three groups from East Malaya: Carboniferous meta-volcanics (n = 2), Permian-Triassic Eastern granite province (EGP) (n = 6), and Permian-Triassic EGP volcanics (n = 8). Difference in magmatic zircon Hf isotopic crustal model ages uphold the previous rationale which separates Peninsular into two blocks: West Malaya (part of Sibumasu terrane) magmatic zircon Hf isotopic crustal model ages (Average TDM2: 1.3 Ga) are older than East Malaya (part of Chanthaburi-Sukhothai-Lincang arc of Indochina terrane) (Average TDM2: 0.9 Ga). During the final assembly of Gondwana from 500 to 450 Ma, West Malaya and East Malaya were at the outboard of Gondwana Proto-Tethys margin. The shift of East Malaya zircon Hf array towards higher εHf(t) (external orogenic system) after ca.370 Ma may infers Paleo-Tethys ocean broadening and East Malaya separation from Gondwana. The 370–350 Ma juvenile zircon Hf isotopic composition in East Malaya is a significant improvement over radiolarian age to show the broadening and subduction of the Paleo-Tethys ocean between the two terranes. After ca.280 Ma, East Malaya zircon Hf array shifted towards lower εHf(t) (internal orogenic system). Coinciding with the Indosinian collision at ca.230 Ma, crustal reworking signal increases in both blocks, signifying the end in Peninsular Malaysia Gondwana to Pangaea transitional geodynamic process. As the Paleo-Tethys segment was completely subducted after 230 Ma, the peninsular crustal thickening starts from 230 to 218 Ma. The post-collision phase would begin at ca.215 Ma.

Geochemical characteristics and Sr‐Nd‐Hf isotope compositions of Late Triassic post‐collisional A‐type granites in Sarudik, SW Sumatra, Indonesia

AbstractLate Triassic A‐type granites are identified in this study in Sarudik, SW Sumatra. We present new data on zircon U–Pb geochronology, whole‐rock major and trace elements and Sr‐Nd‐Hf isotope geochemistry, aiming to study their petrogenesis and tectonic implications. LA‐ICP‐MS U–Pb dating of zircon separated from one biotite monzogranite sample yields a concordia age of 222.6 ±1.0 Ma, indicating a Late Triassic magmatic event. The studied granites are classified as weakly peralumious, high‐K calc‐alkaline granites. They exhibit high SiO2, K2O + Na2O, FeO/(FeO + MgO) and Ga/Al ratios and low Al2O3, CaO, MgO, P2O5 and TiO2 contents, with enrichment of Rb, Th and U and depletion of Ba, Sr, P and Eu, showing the features of A‐type granites. The granites have zircon εHf(t) values from −4.6 to −0.4 and whole‐rock εNd(t) values from −5.51 to −4.98, with Mesoproterozoic TDM2 ages (1278–1544 Ma) for both Hf and Nd isotopes. Geochemical and isotopic data suggest that the source of these A‐type granites is the Mesoproterozoic continental crust, without significant incorporation of mantle‐derived component, and their formation is controlled by subsequent fractional crystallization. The Sarudik A‐type granites are further assigned to A2‐type formed in post‐collisional environment. Combined with previous knowledge on the western SE Asia tectonic evolution, we conclude that the formation of the Late Triassic A‐type granites is related to the post‐collisional extension induced by the crustal thickening, gravitational collapse, and asthenosphere upwelling following the collision between the Sibumasu and the East Malaya Block.

The igneous rocks of Singapore: New insights to Palaeozoic and Mesozoic assembly of the Sukhothai Arc

Six plutons of granitic to gabbroic rocks have been recognised in the poorly exposed ground of north and east Singapore using new data from borehole cores and field observations. Five of the plutons were emplaced sequentially during the period 285–230 Ma, and these have been grouped within a single parent unit (Bukit Timah Centre) in a new lithodemic framework for Singapore. These plutons record the development of early Permian to Triassic arc-related magmatism towards the southern end of the Sukhothai Arc system of Thailand, Peninsular Malaysia and Indonesia. Compositional trends in the plutons record decreasing crustal contribution as the arc matured. The volcanosedimentary succession underlying southwest Singapore records contemporaneous deposition in the forearc basin, and includes pyroclastic units of sufficient thickness and extent to be assigned ‘member’ status in a new lithostratigraphical framework for Singapore. The largest pyroclastic unit, which is >150 m thick, developed as volcanic activity peaked at c. 242 Ma and is correlated with a large (probably caldera-forming) eruption of one of the Permo-Triassic plutons. The composition, typology and age of the Bukit Timah Centre plutons confirm their affinity with Eastern Belt intrusions of the Eastern Province (one of three granitoid provinces in Southeast Asia), and support a widely accepted model that Eastern Province granitoids formed in an Andean-type setting as Palaeo-Tethys crust descended beneath the Indochina–East Malaya block. Widespread development of hydrothermal-tuffisite in the Permo-Triassic intrusions is correlated tentatively with rapid uplift following slab breakoff, when arc activity ceased in the Singapore region in the interval c. 230–205 Ma. A sixth pluton, much younger than (and unrelated to) the Bukit Timah Centre, was emplaced in northeast Singapore in the Upper Cretaceous.

First evidence of Middle to Late Triassic radiolarians in the Garba mountains, South Sumatra, Indonesia

AbstractA Middle to Late Triassic (Ladinian–Carnian) radiolarian fauna was discovered in cherts of the Situlanglang Member of the Garba Formation, South Sumatra, which is generally regarded as of Late Jurassic–Early Cretaceous age. This fauna is characterized by the presence of Annulotriassocampe sulovensis, Triassocampe postdeweveri, Spongotortilispinus tortilis, Poulpus piabyx, Canoptum levis and others. This evidence possibly indicates that the deposition of the Situlanglang cherts took place after the collision of the Sibumasu and East Malaya blocks recorded in the Bentong–Raub Suture in Peninsular Malaysia in Late Permian–Early Triassic times. During the Middle–Late Triassic Sumatra and Peninsular Malaysia consisted of submarine horst and graben structures. It is possible that a submarine graben, the Tuhur basin, whose southern boundary was formerly undefined, extends into South Sumatra, to the area in which the Situlanglang cherts were deposited. The Situlanglang Member is proposed to be a rock unit stratigraphically contemporaneous with those of the Middle–Upper Triassic Kualu and Tuhur Formations in North and Central Sumatra.

The eastern Sundaland margin in the latest Cretaceous to Late Eocene: Sediment provenance and depositional setting of the Kuching and Sibu Zones of Borneo

The Kuching Zone in Borneo comprises several large sedimentary basins of Late Cretaceous to Late Eocene age. In West Sarawak the Kayan Basin includes the Upper Cretaceous to Lower Eocene Kayan Group and further east in the Kuching Zone is the Ketungau Basin, consisting of the Middle to Upper Eocene Ketungau Group.The Kayan Group is composed of the Kayan Sandstone and the Penrissen Sandstone. U-Pb detrital zircon ages and heavy minerals from the Kayan Sandstone suggest two major drainage systems: 1) Late Cretaceous to Paleocene rivers supplied sediment with abundant Cretaceous, Permian-Triassic and Precambrian zircons primarily from SW Borneo and East Malaya–Indochina and 2) Paleocene to Early Eocene rivers provided sediment containing almost entirely Cretaceous zircons from the Schwaner granites of SW Borneo. Differences in heavy minerals and zircon ages of the Lower Eocene Penrissen Sandstone support interpretations of an unconformity above Kayan Sandstone.The Ketungau Group is interpreted to be unconformably above the Kayan Group, representing a new basin. The Ngili Sandstone, the oldest formation of the group, contains sediment derived from nearby sources, probably the Triassic Sadong and Kuching Formations. The Middle to Upper Eocene Bako-Mintu Sandstone, Silantek Formation and the probable Upper Eocene Tutoop Sandstone have similar sources to the Kayan Sandstone and have partly reworked the underlying sediments.Field observations, heavy minerals and U-Pb zircon age data identify a large depositional system passing from the Kuching Zone terrestrial setting into Sibu Zone Rajang Group submarine fan deposits. This system was active for at least 25 to 30 Ma and at times the catchment area extended into the Malay Peninsula, possibly Sibumasu. The Kuching Supergroup sediments can be correlated with deep marine Rajang Group sediments based on detrital zircon ages and heavy mineral assemblages. There was some magmatism but the scarcity of contemporaneous zircons and compositional maturity of heavy mineral assemblages indicates that it was very minor. There is no support for subduction magmatism and the new observations are inconsistent with models suggesting the Sibu Zone was the source of sediments for a Kuching Zone forearc basin.

Implications of U–Pb detrital zircon geochronology analysis for the depositional age, provenance, and tectonic setting of continental Mesozoic formations in the East Malaya Terrane, Peninsular Malaysia

Mesozoic strata in the East Malaya Terrane of Peninsular Malaysia record a long but poorly constrained history of basin evolution. In this study, we report LA‐ICP‐MS U–Pb geochronology analyses of detrital zircons in the continental Mesozoic sequences from the Bertangga and Gerek formations of Peninsular Malaysia, with the aim to constrain the depositional ages and provenances of the continental Mesozoic strata as well as the Mesozoic tectonic evolution of the East Malaya Terrane. The Bertangga Formation yields populations of U–Pb zircon ages of Jurassic (139 to 194 Ma), Permo−Triassic (226 to 274 Ma), Ordovician−Devonian (372 to 459 Ma), Neoproterozoic (631 to 876 Ma), and Mesoproterozoic−Palaeoproterozoic (1,448 to 2,629 Ma). In contrast, the Gerek Formation yields significant Carboniferous grains, but with an approximate zircon age range relative to the Bertangga Formation. The new data indicate a maximum Late Jurassic depositional age for the previously undated Bertangga Formation. Similarly, young zircon grain ages in the Gerek Formation also indicate a maximum Late Jurassic depositional age. Collectively, these results on detrital zircons correlate well with a regional tectonic uplift and erosion to a tectonic stability of the East Malaya Terrane basin during the Mesozoic.

The Mesozoic tectono-magmatic evolution at the Paleo-Pacific subduction zone in West Borneo

Metamorphic and magmatic rocks are present in the northwestern part of the Schwaner Mountains of West Kalimantan. This area was previously assigned to SW Borneo (SWB) and interpreted as an Australian-origin block. Predominantly Cretaceous U-Pb zircon ages (c. 80–130Ma) have been obtained from metapelites and I-type granitoids in the North Schwaner Zone of the SWB but a Triassic metatonalite discovered in West Kalimantan near Pontianak is inconsistent with a SWB origin. The distribution and significance of Triassic rocks was not known so the few exposures in the Pontianak area were sampled and geochemical analyses and zircon U-Pb ages were obtained from two meta-igneous rocks and three granitoids and diorites. Triassic and Jurassic magmatic and metamorphic zircons obtained from the meta-igneous rocks are interpreted to have formed at the Mesozoic Paleo-Pacific margin where there was subduction beneath the Indochina–East Malaya block. Geochemically similar rocks of Triassic age exposed in the Embuoi Complex to the north and the Jagoi Granodiorite in West Sarawak are suggested to have formed part of the southeastern margin of Triassic Sundaland. One granitoid (118.6±1.1Ma) has an S-type character and contains inherited Carboniferous, Triassic and Jurassic zircons which indicate that it intruded Sundaland basement. Two I-type granitoids and diorites yielded latest Early and Late Cretaceous weighted mean ages of 101.5±0.6 and 81.1±1.1Ma. All three magmatic rocks are in close proximity to the meta-igneous rocks and are interpreted to record Cretaceous magmatism at the Paleo-Pacific subduction margin. Cretaceous zircons of metamorphic origin indicate recrystallisation at c. 90Ma possibly related to the collision of the Argo block with Sundaland. Subduction ceased at that time, followed by post-collisional magmatism in the Pueh (77.2±0.8Ma) and Gading Intrusions (79.7±1.0Ma) of West Sarawak.

Geology and fluid characteristics of the Ulu Sokor gold deposit, Kelantan, Malaysia: Implications for ore genesis and classification of the deposit

The Ulu Sokor gold deposit is one of the most famous and largest gold deposits in Malaysia and is located in the Central Gold Belt. This deposit consists of three major orebodies that are related to NS- and NE-striking fractures within fault zones in Permian-Triassic meta-sedimentary and volcanic rocks of the East Malaya Block. The faulting events represent different episodes that are related to each orebody and are correlated well with the mineralogy and paragenesis. The gold mineralization consists of quartz-dominant vein systems with sulfides and carbonates. The hydrothermal alteration and mineralization occurred during three stages that were characterized by (I) silicification and brecciation; (II) carbonatization, sericitization, and chloritization; and (III) quartz–carbonate veins.Fluid inclusions in the hydrothermal quartz and calcite of the three stages were studied. The primary CO2–CH4–H2O–NaCl fluid inclusions in stage I are mostly related to gold mineralization and display homogenization temperatures of 269–389°C, salinities of 2.77–11.89wt.% NaCl equivalent, variable CO2 contents (typically 5–29mol%), and up to 15mol% CH4. In stage II, gold was deposited at 235–398°C from a CO2±CH4–H2O–NaCl fluid with a salinity of 0.83–9.28wt.% NaCl equivalent, variable CO2 contents (typically 5–63mol%), and up to 4mol% CH4. The δ18OH2O and δD values of the ore-forming fluids from the stage II quartz veins are 4.5 to 4.8‰ and −44 to −42‰, respectively, and indicate a metamorphic–hydrothermal origin. Oxygen fugacities calculated for the entire range of T-P-XCO2 conditions yielded log fO2 values between −28.95 and −36.73 for stage I and between −28.32 and −39.18 for stage II. These values indicate reduced conditions for these fluids, which are consistent with the mineral paragenesis, fluid inclusion compositions, and isotope values.The presence of daughter mineral-bearing aqueous inclusions is interpreted to be a magmatic signature of stage IIIa. Combined with the oxygen and hydrogen isotopic compositions (δ18OH2O=6.8 to 11.9‰, δD=−77 to −62‰), these inclusions indicate that the initial fluid was likely derived from a magmatic source. In stage IIIb, the gold was deposited at 263° to 347°C from a CO2–CH4–H2O–NaCl fluid with a salinity of 5.33 to 11.05wt.% NaCl equivalent, variable CO2 contents (typically 9–15mol%), and little CH4. The oxygen and hydrogen isotopic compositions of this fluid (δ18OH2O=8.1 to 8.8‰, δD=−44 to −32‰) indicate that it was mainly derived from a metamorphic–hydrothermal source. The CO2–H2O±CH4–NaCl fluids that were responsible for gold deposition in the stage IIIc veins had a wide range of temperatures (214–483°C), salinities of 1.02 to 21.34wt.% NaCl equivalent, variable CO2 contents (typically 4–53mol%), and up to 7mol% CH4. The oxygen and hydrogen isotopic compositions (δ18OH2O=8.5 to 9.8‰, δD=−70 to −58‰) were probably acquired at the site of deposition by mixing of the metamorphic–hydrothermal fluid with deep-seated magmatic water and then evolved by degassing at the site of deposition during mineralization. The log fO2 values from −28.26 to −35.51 also indicate reduced conditions for this fluid in stage IIIc. Moreover, this fluid had a near-neutral pH and δ34S values of H2S of −2.32 to 0.83‰, which may reflect the derivation of sulfur from the subducted oceanic lithospheric materials.The three orebodies represent different gold transportation and precipitation models, and the conditions of ore formation are related to distinct events of hydrothermal alteration and gold mineralization. The gold mineralization of the Ulu Sokor deposit occurred in response to complex and concurrent processes involving fluid immiscibility, fluid–rock reactions, and fluid mixing. However, fluid immiscibility was the most important mechanism for gold deposition and occurred in these orebodies, which have corresponding fluid properties, structural controls, geologic characteristics, tectonic settings, and origins of the ore-forming matter. These characteristics of the Ulu Sokor deposit are consistent with its classification as an orogenic gold deposit, while some of the veins are genetically related to intrusions.

Structural evolution of Malay Basin, its link to Sunda Block tectonics

The Malay Basin is located offshore West Malaysia in the South China Sea, within north central region of 1st order Sunda Block. The basin developed partly as a result of tectonic collisions and strike-slip shear of the Southeast Asia continental slabs, as the Indian Plate collided into Eurasia, and subsequent extrusion of lithospheric blocks towards Indochina. The Sunda Block epicontinental earliest rift margins were manifested by the Palaeogene W–E rift valleys, which formed during NW–SE sinistral shear of the region. Later Eocene NW–SE dextral shear of (2nd order) Indochina Block against East Malaya Block rifted open a 3rd order Malay Basin. Developed within it is a series of 4th order N–S en-echelon ridges and grabens. The grabens and some ridges, sequentially, host W–E trending 5th order folds of later compressional episodes. The Malay Basin Ridge and Graben Model explains the multi-phased structural deformation which started with, the a) Pre-Rift Palaeo/Mesozoic crystalline/metamorphic Basement, b) Synrift phase during Paleogene, c) Fast Subsidence from Late Oligocene to Middle Miocene, d) Compressional inversion of first Sunda fold during Late Miocene, and e) Basin Sag during Plio-Pleistocene with mild compressional episodes. The subsequent Mio-Pliocene folding history of Malay Basin is connected to the collision of Sunda Block against subducting Indian–Australian Plate. This Neogene Sunda tectonics, to some degree after the cessation of South China Sea spreading, is due to the diachronous collision along the 1st order plate margins between SE Asia and Australia.

Chert blocks in Bentong-Raub Suture Zone: A heritage of Palaeo-Tethys

Bentong-Raub Suture Zone is considered as a collision zone between the Sibumasu and East Malaya (Indochina) terranes. Sibumasu was a part of the Cimmerian plate, which was attached to Gondwana during the Carboniferous. East Malaya was attached to the Indochina plate. From the Devonian to the Permian the Sibumasu and East Malaya blocks were separated by an ocean called Palaeo-Tethys. The closure of Palaeo-Tethys was completed during the Triassic. The major part of the history of the Palaeo-Tethys was destroyed and only a small portion is still preserved in blocks of oceanic sedimentary rocks such as cherts. The chert blocks are exposed in several localities along the Bentong-Raub road (3°35'N, 101°54'E), Gua Musang-Cameron Highland road (4°45'N, 101°45'E) and at a road-cut in Langkap (2°38'N, 102°21'E). The chert blocks consist of thinly bedded chert interbeded with mudstone. Some chert layers contain radiolarians. The oldest chert block found at Bentong-Raub road-cut yielded an assemblage of radiolarians belonging to the Trilonche minax Zone of early Frasnian, (early Late Devonian) age. A chert block from Langkap, Negeri Sembilan yielded radiolarians belonging to the Albaillella deflandrei Assemblage Zone, Tournaisian, (Early Carboniferous) age. Permian radiolarians were retrieved from several chert blocks in the vicinity of Pos Blau, Ulu Kelantan. The youngest radiolarian assemblage in the area is from the Follicucullus monacanthus Assemblage Zone indicating Wordian, (Middle Permian) age. The occurrence of radiolarian chert suggests high plankton productivity during the Late Devonian, Early Carboniferous and Permian. These chert blocks are the natural heritage of the Paleo-Tethys which needed to be conserved as National Heritage sites.