Tourmaline Composition of the Kı¸sladag Porphyry Au Deposit,Western Turkey: Implication of Epithermal Overprint

The Kışladağ porphyry Au deposit occurs in a middle Miocene magmatic complex comprising three different intrusions and magmatic-hydrothermal brecciation related to the multiphase effects of the different intrusions. Tourmaline occurrences are common throughout the deposit, mostly as an outer alteration rim around the veins with lesser amounts disseminated in the intrusions, and are associated with every phase of mineralization. Tourmaline mineralization has developed as a tourmaline-rich matrix in brecciated zones and tourmaline-quartz and/or tourmaline-sulfide veinlets within the different intrusive rocks. Tourmaline was identified in the tourmaline-bearing breccia zone (TBZ) and intrusive rocks that had undergone potassic, phyllic, and advanced argillic alteration. The tourmaline is present as two morphological varieties, aggregates of fine crystals (rosettes, fan-shaped) and larger isolated crystals and their aggregates. Four tourmaline generations (tourmaline I to IV) have different compositions and substitutions. Tourmaline I in TBZ and INT#1 is distinguished by the highest Fetot and enriched in Fe3+. Tourmalines II and III occur as fine aggregates, accompanied by the formation of isolated crystals and are characterized by lower Fetot and Fe3+. Tourmaline IV is characterized by the lowest Fetot, enriched in Cl, and has the highest proportion of X-site vacancy among all the tourmalines. Tourmaline I may be attributed to the potassic stage in INT#1 and early tourmaline in TBZ. Tourmalines II and III from INT#1 and the TBZ could be referred to the phyllic stage. The low Fe content in tourmaline is caused by the simultaneous deposition of sulfide minerals. Tourmaline IV from the TBZ and tourmaline II from INT#3 are distinguished by the high X-site vacancy proportion up to the formation of X-site vacant species as well as enriched in Cl; they can be attributed to the argillic stage of the hydrothermal process. The textural and especially chemical data of the tourmaline from the Kışladağ Au deposit provide information on the physico-chemical conditions during the porphyry to epithermal transition and subsequent epithermal overprinting

Çöpler (Erzincan, İç-Doğu Anadolu) Porfiri-Epitermal Altın Yatağında Arjilik Alterasyona İlişkin Mineralojik Kanıtlar (Mineralogical Evidences on Argillic Alteration in the Çöpler Porphyry-Epithermal Gold Deposit) (Erzincan, East-Central Anatolia)

Çöpler porfiri-epitermal altın yatağı, Tetis Alpin-Himalaya orojenik kuşağında açılmalı tektonizma sonucu gelişen orta Eosen yaşlı plütonik sokulumlarla ilişkili bir altın yatağıdır. Plütonik kayaçlar (granodiyorit porfir, diyorit porfir) Geç Paleozoyik-Mesozoyik yaşlı metapelit ve metakarbonat kayaçlar içerisine sokulum yaparak porfiri-epitermal bir Cu-Au yatağı oluşturmuş ve hidrotermal alterasyon zonlarının (potasik, fillik, propilitik, arjilik) gelişimine neden olmuştur. Bu çalışmada, önceki araştırmacılarca yerel ve sınırlı alanda geliştiği belirtilen süperjen alterasyonun aksine, geniş yayılım sunan arjilik alterasyon zonlarının mineralojik-petrografik özelliklerinin ortaya konulması amaçlanmıştır. Bu kapsamda, optik ve taramalı elektron mikroskop (SEM ve SEM-EDS), X-ışınları kırınımı (XRD), O-H izotop jeokimyası ve K/Ar yaş tayini incelemeleri gerçekleştirilmiştir. Aşırı killeşmiş granodiyorit porfirlerde bile, ilksel porfiritik doku izlenebilmekte, ince-kristalli kil ve kuvarslar homojen ve yer yer mikrolaminasyonlar şeklinde gözlenmektedir. Simektit ve karışık-tabakalı illit-simektit (I-S) mineralleri yapraksıtüysü, illit ve kaolinitler levhamsı biçimler sergilemektedir. Kuvars ve jarositler özşekilli kristaller, kristobalitler kurtçuk görünümlü, bu çalışmada ilk kez belirlenen krandallitler ise ince-taneli granüler topluluklar şeklinde gözlenmektedir. Arjilik zona ait örnekler fillik zona yakın iç kesimlerde (ileri arjilik zon) kuvars + I-S, kuvars + krandallit + jarosit ve kristobalit, dış kesimlerde (arjilik zon) ise kuvars + simektit + kaolinit birliktelikleri sergilemektedir. Simektitler dioktahedral bileşime sahiptir (d060<1.500 Å, oktahedral Al=1.47-1.66). I-S mineralleri yüksek illit bileşenli (I85-S15) ve R3 tipi ara tabakalanmaya sahip olup, oktahedral Al ve yapraklar arası K içerikleri sırasıyla 1.66-1.71 ve 0.58-0.75 arasında değişmektedir. I-S’lerin O-H izotop bileşimi, düşük sıcaklık koşullarında ve magmatik suyun baskın olduğu bir oluşumu işaret etmektedir. Jarosit içeren örneğin K/Ar yaş verisi (43.6 ± 1.0 My), arjilik alterasyonun plütonik sokulum sırasında veya hemen sonrasında (<1 My) başladığına işaret etmektedir. Elde edilen bulgular, Çöpler porfiriepitermal altın yatağında geniş yayılım sunan, düşük sıcaklık (<200 ºC) ve asidik koşullarda gelişmiş, alüminyum fosfat ve demir sülfat minerallerinin de geliştiği bir arjilik alterasyonun varlığını ortaya koymaktadır. (The Çöpler porphyry-epithermal gold deposit is associated with middle Eocene intrusive rocks related to an extensional tectonic phase in the Tethyan Alpine-Himalayan orogenic belt. The intrusive rocks (granodiorite porphyry and diorite porphyry) were emplaced into Late Paleozoic–Mesozoic metapelite and metacarbonate rocks creating the porphyry-epithermal Cu-Au deposit and hydrothermal alteration zones (potassic, phyllic, propylitic, argillic). The mineralogic-petrographic and geochemical properties of the extensive argillic alteration zones (not supergene alteration described previously) were determined by optical and scanning electron microscopy (SEM and SEM-EDS), X-ray diffraction (XRD), O-H isotope geochemistry and K-Ar dating. Within the primary porphyritic texture, fine-grained clay and quartz crystals are present as homogeneous and partly micro-laminations in the more intensely argillized granodiorite porphyry. Smectite and mixed-layer illite-smectite (I-S) minerals exhibit flaky/sponge-like and fibrous shapes, respectively, whereas illites and kaolinites show platy/tabular crystal shapes. Quartz and jarosite have euhedral crystals, cristobalites and crandallites (first determined here) are shown as worm-like and fine-grained granular aggregates, respectively, developed within the pores indicating direct precipitation from the hydrothermal fluids. The samples from the argillic zone display quartz + I-S in the inner parts (advanced argillic zone) close to phyllic zone, whereas quartz + smectite + kaolinite associations are towards outer parts (argillic zone). Smectites have a dioctahedral composition (d060<1.500 Å, octahedral Al=1.47-1.66 a.p.f.u). I-S minerals have a high illite component (I85-S15) with R3 type ordering of interlayering. The tetrahedral Al and interlayer K contents are 1.66-1.71 and 0.58-0.75, respectively. Oxygen and hydrogen isotope composition of I-S indicate the low temperature conditions from the magmatic water dominant fluids. K/Ar age data from jarosite-bearing sample (43.6±1.0 My) indicates that the argillic alteration started during or shortly after (<1 Ma) the plutonic intrusion. The data demonstrate the argillic alteration was widely distributed and developed under low temperature (<200 ºC), acidic conditions in association with the aluminum phosphate and iron phosphate minerals.

Genome-Wide Transcriptional Reorganization Associated with Senescence-to-Immortality Switch during Human Hepatocellular Carcinogenesis

Cataloged from PDF version of article.Senescence is a permanent proliferation arrest in response to cell stress such as DNA damage. It contributes strongly to tissue aging and serves as a major barrier against tumor development. Most tumor cells are believed to bypass the senescence barrier (become "immortal") by inactivating growth control genes such as TP53 and CDKN2A. They also reactivate telomerase reverse transcriptase. Senescence-to-immortality transition is accompanied by major phenotypic and biochemical changes mediated by genome-wide transcriptional modifications. This appears to happen during hepatocellular carcinoma (HCC) development in patients with liver cirrhosis, however, the accompanying transcriptional changes are virtually unknown. We investigated genome-wide transcriptional changes related to the senescence-to-immortality switch during hepatocellular carcinogenesis. Initially, we performed transcriptome analysis of senescent and immortal clones of Huh7 HCC cell line, and identified genes with significant differential expression to establish a senescence-related gene list. Through the analysis of senescence-related gene expression in different liver tissues we showed that cirrhosis and HCC display expression patterns compatible with senescent and immortal phenotypes, respectively; dysplasia being a transitional state. Gene set enrichment analysis revealed that cirrhosis/senescence-associated genes were preferentially expressed in non-tumor tissues, less malignant tumors, and differentiated or senescent cells. In contrast, HCC/immortality genes were up-regulated in tumor tissues, or more malignant tumors and progenitor cells. In HCC tumors and immortal cells genes involved in DNA repair, cell cycle, telomere extension and branched chain amino acid metabolism were up-regulated, whereas genes involved in cell signaling, as well as in drug, lipid, retinoid and glycolytic metabolism were down-regulated. Based on these distinctive gene expression features we developed a 15-gene hepatocellular immortality signature test that discriminated HCC from cirrhosis with high accuracy. Our findings demonstrate that senescence bypass plays a central role in hepatocellular carcinogenesis engendering systematic changes in the transcription of genes regulating DNA repair, proliferation, differentiation and metabolism

Hybrid Meta-heuristics with VNS and Exact Methods: Application to Large Unconditional and Conditional Vertex p-Centre Problems

Large-scale unconditional and conditional vertex p-centre problems are solved using two meta-heuristics. One is based on a three-stage approach whereas the other relies on a guided multi-start principle. Both methods incorporate Variable Neighbourhood Search, exact method, and aggregation techniques. The methods are assessed on the TSP dataset which consist of up to 71,009 demand points with p varying from 5 to 100. To the best of our knowledge, these are the largest instances solved for unconditional and conditional vertex p-centre problems. The two proposed meta-heuristics yield competitive results for both classes of problems

Direct Observation and Measurement of Au and Ag in Epithermal Mineralizing Fluids

Colloidal gold particles have been observed in c. 300 °C low salinity fluids from the Arapucandere intermediate sulphidation epithermal base-metal-Au deposit in NW Turkey. This is the first time colloidal gold has been recorded in an ancient mineralizing fluid. Growth, in veins, of large euhedral quartz crystals, after the deposition of sulphides, occurred in a number of stages from the introduction of fresh pulses of fluid. The quartz overgrowths have a fibrous texture which facilitated trapping of large elongate fluid inclusions between the quartz fibres which grew perpendicular to the crystal faces of the pre-existing quartz. Episodic periods of intense trapping of fluid inclusions occurred throughout the growth of quartz. Trapped within primary fluid inclusions are numerous particles of gold, the largest observed is c. 1 μm but most are smaller. BSE element mapping shows these to contain Au, Ag, Cu ± Hg. LA-ICP-MS profiles of the fluid inclusions confirm Au and Ag is not present in solution, being present as numerous particles. We have quantified the concentration of gold in fluid inclusions which are orders of magnitude greater than has been previously measured or thought likely in crustal fluids. The average Ag concentration is c. 32 ppm and Au is c. 41 ppm but the maximum concentrations of both may reach several 100’s to 1000 ppm. Calcite forms a coating on the inner surface of the inclusions and barite, pyrite, galena, sphalerite and unidentified minerals are also present with the Au-Ag particles. It is clear that the Au-Ag particles could not have precipitated in the fluid inclusions, therefore they must have precipitated elsewhere and been carried with the hydrothermal fluid. The high concentrations and their colloidal nature have implications for the enrichment of gold in mineral deposits

The presence of colloidal gold in epithermal mineralizing fluids

Transport of gold and silver as colloidal particles has been observed in c. 300OC low salinity fluids from the Arapucandere intermediate sulphidation epithermal base-metal-Au deposit in NW Turkey. Large euhedral quartz crystals, grew after the deposition of sulfides. Overgrowths have a fibrous texture which grew perpendicular to the existing crystal faces and facilitated trapping of large elongate fluid inclusions between the quartz fibres. Episodic trapping of fluid inclusions occurred throughout the growth of quartz. Trapped within primary fluid inclusions are numerous particles of gold, the largest observed is c. 1 μm but most are smaller. BSE element mapping show these to contain Au, Ag, Cu + Hg. LA-ICP-MS ablation of fluid inclusions confirms Au and Ag is not present in solution, occurring as numerous particles. The concentration of gold in fluid inclusions is orders of magnitude greater than has been previously measured or thought likely in crustal fluids. The average Ag concentration is c. 32 ppm and Au is c.41 ppm, but the maximum concentrations may reach several 100’s to 1000 ppm. Au-Ag particles could not have precipitated in the fluid inclusions, therefore have precipitated elsewhere and transported by the hydrothermal fluid