The geology and genesis of the iron skarns of the Turgai belt, northwestern Kazakhstan

인도네시아 까시한 지역 함 동-아연 스카른광체는 올리고신 후기 퇴적암류 중 석회암층을 따라 발달한다. 스카른광체의 괴상스카른대는 초기에서 후기로 단사휘석-석류석대, 석류석대, 석류석-녹염석대, 녹염석대 스카른으로 구분된다. 초기 괴상 스카른대에서 산출하는 단사휘석은 투휘석-헤덴버가이트 고용체로서, 초기 투휘석 단성분에 가까운 조성으로부터 후기 salitic 단사휘석으로의 조성변화가 확인된다. 이러한 단사휘석의 조성변화는 일반적인 스카른 광체에서의 수반 금속성분 (Cu 및 Zn광화작용)과 단사휘석 조성 상관관계와 잘 일치한다. 석류석의 경우 그로슐라-안드라다이트 고용체로서 매우 넓은 조성변화를 보여주며, 후기 석류석의 경우 Fe함량의 증가 경향성이 인지된다. 녹염석의 경우 클리노조이사이트-피스타사이트 고용체(65.8-76.2 mol. % 클리노조이사이트)로 확인된다. 상평형관계로 확인된 까시한 지역 함 동-아연 스카른광체는 약 0.5 kb의 환경에서 초기 약 $450^{\circ}C$ (단사휘석-석류석 및 석류석 스카른, ${\approx}450-370^{\circ}C$) 에서 시작되어 후기 $300^{\circ}C$ (석류석-녹염석 및 녹염석 스카른, ${\approx}370-300^{\circ}C$) 에 걸쳐 진행되었다. Copper-zinc-bearing skarns of the Kasihan area developed at limestone layers in the sedimentary facies of the Late Oligocene Arjosari Formation. The skarns consist mainly of fine-grained, massive clinopyroxene-garnet, garnet, garnet-epidote, and epidote skarns. Most copper and zinc(-lead) ore mineralization occur in the clinopyroxene-garnet and garnetepidote skarn, respectively. Clinopyroxene occurs as a continuous solid solution of diopside and hedenbergite (from nearly pure diopside up to ${\approx}34$ mole percent hedenbergite), with a maximum 28.2 mole percent johannsenite component. The early and late pyroxenes of Kasihan skarns are diopsidic and salitic, respectively. They fall in the fields typical Cu- and Zn-dominated skarns, respectively. Garnet displays a relatively wide range of solid solution between grossular and andradite with up to ${\approx}2.0$ weight percent MnO. Garnet in early pyroxene-garnet skarn ranges from 49.1 to 91.5 mole percent grossular (mainly ${\geq}78$ mole % grossular). Garnets in late garnet and garnet-epidote skarns range from 2.8 to 91.4 mole percent grossular (mainly ${\geq}70$ mole % for garnet skarn). Epidote compositions indicate solid solutions of clinozoisite and pistacite varying from 65.8 to 76.2 mole percent clinozoisite. Phase equilibria indicate that skarn evolution was the result of interaction of water-rich fluids ($X_{CO_2}{\leq}0.1$) with original lithologies at ${\approx}0.5$ kb with declining temperature (early clinopyroxene-garnet and garnet skarn, ${\approx}450$ to $370^{\circ}C$; late garnet-epidote and epidote skarn, ${\approx}370$ to $300^{\circ}C$).

Grossular

Diopside

Andradite

Paragenesis

Pyroxene

10.9719/eeg.2012.45.1.001

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Mineralogy, Geochemistry, and Age Constraints on the Axinite-Bearing Gukjeon Pb–Zn Skarn Deposit in the Miryang Area, South Korea

Minerals (2021)

Namhoon Kim Sang‐Mo Koh Byoung-Woon You Bum Han Lee

The axinite-bearing Gukjeon Pb–Zn deposit is hosted by the limestone, a member of the Jeonggaksan Formation, which, in turn, forms the part of the Jusasan subgroup of the Yucheon Group in the Gyeongsang Basin in the southeastern part of the Korean Peninsula. In this study, we attempted to interpret the spatial and temporal relationships among geologic events, including the mineralization of this deposit. We constructed a new 3D orebody model and suggested a relationship between skarn alteration and related mineralization. Mineralization timing was constrained using SHRIMP zircon age dating results combined with boron geochemistry on coeval intrusive rocks. Skarn alterations are restrictively found in several horizons of the limestone formation. The major skarn minerals are garnet (grossular), pyroxene (hedenbergite), amphibole (actinolite and ferro-actinolite), axinite (tizenite and ferro-axinite), and epidote (clinozoisite and epidote). The three stages of pre-skarn, syn-skarn, and post-skarn alteration are recognized within the deposit. The syn-skarn alteration is characterized by prograde metasomatic pyroxene and garnet, and the retrograde metasomatic amphibole, axinite, and epidote. Major skarn sulfide minerals are sphalerite, chalcopyrite, galena, and pyrite, which were predominantly precipitated during the retrograde stage and formed amphibole and axinite skarns. The skarn orebodies seem to be disc- or flat-shaped with a convex form at the central part of the orebodies. The vertical ascending and horizontal infiltration of boron-rich hydrothermal fluid probably controlled the geometry of the orebodies. Considering the whole-rock major, trace, and boron geochemical and geochronological results, the timing of Pb–Zn mineralization can be tightly constrained between the emplacement of boron-poor intrusion (fine-grained granodiorite, 82.8 Ma) and boron-rich intrusion (porphyritic andesite in Beomdori andesitic rocks, 83.8 Ma) in a back-arc basin setting. The boron for mineralization was sourced from late Cretaceous (Campanian), subduction-related magmatic rocks along the margin of the Pacific plate.

Actinolite

Metasomatism

Amphibole

Andradite

Pyroxene

Ore genesis

10.3390/min11060619

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Skarn mineral characteristics of Mengku iron deposit in Xinjiang and their geological significance

Mineralium Deposita (2007)

Lin Xu

Andradite

Actinolite

Amphibole

Grossular

Pyroxene

Paragenesis

Diopside

Source

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Citations (1)

Metallogeny of the Handagai skarn Fe–Cu deposit, northern Great Xing'an Range, NE China: Constraints on fluid inclusions and skarn genesis

Ore Geology Reviews (2016)

Zhenhua Zhou Jingwen Mao Hewei Che Hegen Ouyang Xinghua Ma

Actinolite

Paragenesis

Andradite

10.1016/j.oregeorev.2016.08.012

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Citations (21)

Skarn Mineralization Zonation and Fluid Evolution in the Jiaoli Deposit, Jiangxi Province

Dizhi lunping (2004)

Yiming Zhao

The Jiaoli Ag-Pb-Zn-W skarn deposit is located in southern Jiangxi Province, China. The orebodies occur in the exocontact zone between a Yanshanian (171. 6-173. 3 Ma) granodiorite and Upper Cambrian metasandstone and crystalline limestone. Skarn mineralization zoning in the deposit is very pronounced. From the intrusive contract zone to country wall rocks, two ore-bearing skarn zones may be distinguished: proximal scheelite-bearing calcic skarn zone and Ag-Pb-Zn-bearing manganoan skarn zone. The W-bearing calcic skarn is composed of grossular, andradite, diopside , wollastonite, scheelite, and f luorite; while the Ag-Pb-Zn-bearing manganoan skarn consists mainly of manganoan grossular, spessartine, manganoan actinolite, and manganoan vesuvianite, associated with sphalerite, galena, pyrrhotite, argentite, silver, and minor scheelite. Study of the fluid inclusions suggests that ore-bearing fluids flowed from the deep contract zone of the intrusion in the west to the shallow depth in the east. With decreasing temperatures and salinities, the peak values of homogenization temperatures in the W-bearing calcic skarn are 420-340℃. Their salinities range from 12. 7% - 8 % (NaCleq ). In the Ag-Pb-Zn-bearing manganoan skarn, the peak values of homogenization temperatures are 360°-320℃ with salinities being 11. 7%-4. 5% (NaCleq). While for late ore-bearing retrograde hydrothermal metasomatic products, fluolite and quartz, their homogenization temperatures range from 380 to 180℃.

Grossular

Actinolite

Metasomatism

Andradite

Scheelite

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Citations (2)